Code 42, HELP!!!
05-29-2016, 09:12 AM
#1
Code 42, HELP!!!
I am going nuts with this stupid code 42. I have replaced so many parts I have lost track.
New temp sensors
new fuel injectors, South Bay
new TPS module
new high performance starter
New EGR Valve and the wire that attaches to it
new hoses for PVC valve and the other side
cleaned the runners and plenum inside
full tune up last year, plugs wires, cap, etc.
Put in a new fuel pump a few years ago.
This all started around when I first installed the new starter late last summer prior to most of the updates above. However I am not sure that this is the cause being the way its acting.
When I try and start the car, it runs for maybe 5 seconds, then dies. I have to do a bunch of times, then it finally catches and runs. Then the check engine light comes on. When I press the gas, major hesitation then it kicks in. Almost like there is a fuel air mixture issue. I cant drive it because it jerks when in drive.
Yesterday I did a smog test for vacuum and found a small leak on the lower hose that goes into the throttle body. Once I fixed that, she started right up, no codes, revs and idles, drivable, PERFECT. This morning back to the same BS above.
Not sure what to do at this point accept have it towed to a dealership and let them fix it. It also needs an inspection which expires on June 1st.
If anyone has any ideas on the stupid code 42 I would really appreciate it. Thanks!
New temp sensors
new fuel injectors, South Bay
new TPS module
new high performance starter
New EGR Valve and the wire that attaches to it
new hoses for PVC valve and the other side
cleaned the runners and plenum inside
full tune up last year, plugs wires, cap, etc.
Put in a new fuel pump a few years ago.
This all started around when I first installed the new starter late last summer prior to most of the updates above. However I am not sure that this is the cause being the way its acting.
When I try and start the car, it runs for maybe 5 seconds, then dies. I have to do a bunch of times, then it finally catches and runs. Then the check engine light comes on. When I press the gas, major hesitation then it kicks in. Almost like there is a fuel air mixture issue. I cant drive it because it jerks when in drive.
Yesterday I did a smog test for vacuum and found a small leak on the lower hose that goes into the throttle body. Once I fixed that, she started right up, no codes, revs and idles, drivable, PERFECT. This morning back to the same BS above.
Not sure what to do at this point accept have it towed to a dealership and let them fix it. It also needs an inspection which expires on June 1st.
If anyone has any ideas on the stupid code 42 I would really appreciate it. Thanks!
Last edited by Hawkeye1980; 05-29-2016 at 09:40 AM.
05-29-2016, 11:06 AM
#2
Re: Code 42, HELP!!!
If you haven't already done so, you need to pick up the GM service manual for your specific car, then flip to the section on Code 42 and follow the flow chart. That's all a dealer is going to do. There's a 90% chance following the chart will fix the problem.
05-29-2016, 11:19 AM
#3
Re: Code 42, HELP!!!
worn throttle body shaft bushings allowing unmetered air in after the maf sensor possibly? I can't remember which code it was but this problem got rid of it for me and made a huge improvement. I'm not sure but I think it was either code 42-44 for me.
tape off the throttle body opening and blow cigar smoke into a vacuum hose that leads right to the throttle body and look for smoke,
tape off the throttle body opening and blow cigar smoke into a vacuum hose that leads right to the throttle body and look for smoke,
05-29-2016, 11:36 AM
#4
Re: Code 42, HELP!!!
worn throttle body shaft bushings allowing unmetered air in after the maf sensor possibly? I can't remember which code it was but this problem got rid of it for me and made a huge improvement. I'm not sure but I think it was either code 42-44 for me.
tape off the throttle body opening and blow cigar smoke into a vacuum hose that leads right to the throttle body and look for smoke,
tape off the throttle body opening and blow cigar smoke into a vacuum hose that leads right to the throttle body and look for smoke,
Last edited by Hawkeye1980; 05-29-2016 at 11:53 AM.
05-29-2016, 01:21 PM
#6
Re: Code 42, HELP!!!
Well according to the GM service manual after performing all the tests, its ether a connection to the 423 wire, or the ignition coil itself. Which might make sense being I replaced it a while ago from Advance Auto parts. I see this unit can have issues based on reviews.
I have an old Excel coil on the car, this is it on ebay:
http://www.ebay.com/itm/261584061426?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
So what ignition module would be best to replace the one I have?
Thanks!
I have an old Excel coil on the car, this is it on ebay:
http://www.ebay.com/itm/261584061426?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
So what ignition module would be best to replace the one I have?
Thanks!
05-29-2016, 01:49 PM
#7
Supreme Member
Re: Code 42, HELP!!!
Well according to the GM service manual after performing all the tests, its ether a connection to the 423 wire, or the ignition coil itself. Which might make sense being I replaced it a while ago from Advance Auto parts. I see this unit can have issues based on reviews.
I have an old Excel coil on the car, this is it on ebay:
(snipped)
So what ignition module would be best to replace the one I have?
Thanks!
I have an old Excel coil on the car, this is it on ebay:
(snipped)
So what ignition module would be best to replace the one I have?
Thanks!
I'd also recommend either testing the coil (if you can find specs) or swap it with an OEM replacement.
I don't know why you're asking about an ignition module; but again go with an OEM replacement.
OEM replacement = ACDelco
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05-29-2016, 02:12 PM
#8
Re: Code 42, HELP!!!
I'd recommend checking the 423 connector as stated in the FSM.
I'd also recommend either testing the coil (if you can find specs) or swap it with an OEM replacement.
I don't know why you're asking about an ignition module; but again go with an OEM replacement.
OEM replacement = ACDelco
I'd also recommend either testing the coil (if you can find specs) or swap it with an OEM replacement.
I don't know why you're asking about an ignition module; but again go with an OEM replacement.
OEM replacement = ACDelco
I was wrong the manual says ckt 424, not 423. Either that is faulty or the ICM is bad. Just not sure how to check the 424 connector.
05-29-2016, 02:14 PM
#9
Re: Code 42, HELP!!!
You can throw parts at it all day, and you might get lucky, but if you gain an understanding of how the systems work, you can isolate the problem and save yourself a bunch of time and headaches replacing parts that are A-OK. That's what the charts and step-by-step procedures in the book are telling you, each step isolates a possible cause of the error and eliminates it from the list. If you're not understanding what the manual is telling you, study whichever part is confusing you until it makes sense. Don't assume or guess.
There are sections in the GM Service Manual that explain how to test the ignition coil. The same goes for the ignition module. You'll notice the manual doesn't tell you to replace an expensive part until every other diagnostic has been performed.
Aside from on the job experience, which most dealership wrench-monkeys won't likely have with a 25 year old vehicle, and potentially some expensive diagnostic or specialty tools, a dealership isn't going to have any super powers that will allow them to fix the problem any easier than you can. They'll just charge you exorbitant labor, shop fees, parts fees, etc and likely bounce you out the door as soon as the intermittent problem goes away once.
PS If your manual isn't about 3 inches thick with the year, make, and basic model of your car printed on the cover, it's not the GM/Helm manual. A Chiltons, Haynes, or even the old Encyclopedia Britannica style service manuals will only get you so far with general information. At best they have copies of what was in the GM/Helm manual.
There are sections in the GM Service Manual that explain how to test the ignition coil. The same goes for the ignition module. You'll notice the manual doesn't tell you to replace an expensive part until every other diagnostic has been performed.
Aside from on the job experience, which most dealership wrench-monkeys won't likely have with a 25 year old vehicle, and potentially some expensive diagnostic or specialty tools, a dealership isn't going to have any super powers that will allow them to fix the problem any easier than you can. They'll just charge you exorbitant labor, shop fees, parts fees, etc and likely bounce you out the door as soon as the intermittent problem goes away once.
PS If your manual isn't about 3 inches thick with the year, make, and basic model of your car printed on the cover, it's not the GM/Helm manual. A Chiltons, Haynes, or even the old Encyclopedia Britannica style service manuals will only get you so far with general information. At best they have copies of what was in the GM/Helm manual.
05-29-2016, 02:22 PM
#10
Re: Code 42, HELP!!!
You can throw parts at it all day, and you might get lucky, but if you gain an understanding of how the systems work, you can isolate the problem and save yourself a bunch of time and headaches replacing parts that are A-OK. That's what the charts and step-by-step procedures in the book are telling you, each step isolates a possible cause of the error and eliminates it from the list. If you're not understanding what the manual is telling you, study whichever part is confusing you until it makes sense. Don't assume or guess.
There are sections in the GM Service Manual that explain how to test the ignition coil. The same goes for the ignition module. You'll notice the manual doesn't tell you to replace an expensive part until every other diagnostic has been performed.
Aside from on the job experience, which most dealership wrench-monkeys won't likely have with a 25 year old vehicle, and potentially some expensive diagnostic or specialty tools, a dealership isn't going to have any super powers that will allow them to fix the problem any easier than you can. They'll just charge you exorbitant labor, shop fees, parts fees, etc and likely bounce you out the door as soon as the intermittent problem goes away once.
PS If your manual isn't about 3 inches thick with the year, make, and basic model of your car printed on the cover, it's not the GM/Helm manual. A Chiltons, Haynes, or even the old Encyclopedia Britannica style service manuals will only get you so far with general information. At best they have copies of what was in the GM/Helm manual.
There are sections in the GM Service Manual that explain how to test the ignition coil. The same goes for the ignition module. You'll notice the manual doesn't tell you to replace an expensive part until every other diagnostic has been performed.
Aside from on the job experience, which most dealership wrench-monkeys won't likely have with a 25 year old vehicle, and potentially some expensive diagnostic or specialty tools, a dealership isn't going to have any super powers that will allow them to fix the problem any easier than you can. They'll just charge you exorbitant labor, shop fees, parts fees, etc and likely bounce you out the door as soon as the intermittent problem goes away once.
PS If your manual isn't about 3 inches thick with the year, make, and basic model of your car printed on the cover, it's not the GM/Helm manual. A Chiltons, Haynes, or even the old Encyclopedia Britannica style service manuals will only get you so far with general information. At best they have copies of what was in the GM/Helm manual.
I have the original manual for this car from GM, its about 4 inches thick actually. bought it years ago, got messed up and found a reprint on eBay a few years ago. Its the right one.
Taking it to the dealer is an act of desperation. I could not drive it last summer and looks to be the same this this time, just frustrating. At least in the test I have proven its NOT the ECM which it can be if certain conditions were met, which they were not.
The exact fix/troubleshoot is:
"CKT 424 open, faulty connections or faulty ignition module"
so with the module being a cheap one I put in a few years ago, I am going with that. I will look into going back to the stock coil as well.
thanks for the input!
05-29-2016, 02:37 PM
#11
Re: Code 42, HELP!!!
CKT 424 is the tan/blk wire with the timing connector by the heater box. Did you clear the codes and check to see if Code 42 came back? Disconnecting the timing connector at any time will set the code until it's cleared. So if you've ever set the timing by the book and haven't cleared the codes since - Code 42. I'm assuming you ran all the tests with test lights and a DVOM at the ECM connectors to isolate the issue?
When it says "CKT 424 open" it means there's a break in the wire somewhere between the ignition module and the ECM. So you could connect one lead of your DVOM to terminal B at the ignition module connector, and the other to BC7 at the ECM and check for continuity. Wiggle wires, etc and see if the continuity breaks at any point. Visually inspect the plugs at both ends, and the timing connector to be sure they're making a solid contact. If it all that checks out OK, you're looking at an ignition module.
When it says "CKT 424 open" it means there's a break in the wire somewhere between the ignition module and the ECM. So you could connect one lead of your DVOM to terminal B at the ignition module connector, and the other to BC7 at the ECM and check for continuity. Wiggle wires, etc and see if the continuity breaks at any point. Visually inspect the plugs at both ends, and the timing connector to be sure they're making a solid contact. If it all that checks out OK, you're looking at an ignition module.
05-29-2016, 02:43 PM
#12
Re: Code 42, HELP!!!
CKT 424 is the tan/blk wire with the timing connector by the heater box. Did you clear the codes and check to see if Code 42 came back? Disconnecting the timing connector at any time will set the code until it's cleared. So if you've ever set the timing by the book and haven't cleared the codes since - Code 42. I'm assuming you ran all the tests with test lights and a DVOM at the ECM connectors to isolate the issue?
When it says "CKT 424 open" it means there's a break in the wire somewhere between the ignition module and the ECM. So you could connect one lead of your DVOM to terminal B at the ignition module connector, and the other to BC7 at the ECM and check for continuity. Wiggle wires, etc and see if the continuity breaks at any point. Visually inspect the plugs at both ends, and the timing connector to be sure they're making a solid contact. If it all that checks out OK, you're looking at an ignition module.
When it says "CKT 424 open" it means there's a break in the wire somewhere between the ignition module and the ECM. So you could connect one lead of your DVOM to terminal B at the ignition module connector, and the other to BC7 at the ECM and check for continuity. Wiggle wires, etc and see if the continuity breaks at any point. Visually inspect the plugs at both ends, and the timing connector to be sure they're making a solid contact. If it all that checks out OK, you're looking at an ignition module.
To check for continuity from the ECM to the ICM, tan/blk wire, what would could I use tool wise? I have a multi meter, if that would work? thanks again, this site is great with all the help and info given!
05-29-2016, 03:24 PM
#13
Re: Code 42, HELP!!!
Yep, Multimeter, digital volt ohm meter, same thing. You can use the OHM setting which is a bit ambiguous or the diode check setting. Diode check just looks for continuity from one lead to the other. Usually it'll be marked with a triangle with a line through it and another perpendicular like a lower case T, and generally the meter will beep when the leads are touched together, or both to anything conductive, etc. What you're looking for is a solid beep, without any pauses when you jiggle the connectors or wires.
It's worth checking for a pinched wire, or bad connection, but chances are pretty good it's the ICM. They like to get hot and fail intermittently. AC Delco isn't bad, but it's not always as good as it used to be. They generally have two lines, one or both may just be another aftermarket brand with an ACDelco branded box.
It's worth checking for a pinched wire, or bad connection, but chances are pretty good it's the ICM. They like to get hot and fail intermittently. AC Delco isn't bad, but it's not always as good as it used to be. They generally have two lines, one or both may just be another aftermarket brand with an ACDelco branded box.
05-29-2016, 03:48 PM
#14
Re: Code 42, HELP!!!
Yep, Multimeter, digital volt ohm meter, same thing. You can use the OHM setting which is a bit ambiguous or the diode check setting. Diode check just looks for continuity from one lead to the other. Usually it'll be marked with a triangle with a line through it and another perpendicular like a lower case T, and generally the meter will beep when the leads are touched together, or both to anything conductive, etc. What you're looking for is a solid beep, without any pauses when you jiggle the connectors or wires.
It's worth checking for a pinched wire, or bad connection, but chances are pretty good it's the ICM. They like to get hot and fail intermittently. AC Delco isn't bad, but it's not always as good as it used to be. They generally have two lines, one or both may just be another aftermarket brand with an ACDelco branded box.
It's worth checking for a pinched wire, or bad connection, but chances are pretty good it's the ICM. They like to get hot and fail intermittently. AC Delco isn't bad, but it's not always as good as it used to be. They generally have two lines, one or both may just be another aftermarket brand with an ACDelco branded box.
05-30-2016, 11:35 AM
#15
Re: Code 42, HELP!!!
So I checked the wires for both diode and OHMS, as well as inspect the wire itself. Everything looks OK. So now I will just wait for the ICM to show up.
As far as the coil goes, I still have the original, it was taken out YEARS ago and replaced with the EXCEL I have. I wonder if its still any good? If not, I know I can get a replacement but they don't have the riveted bracket built in. Can anyone suggest a good OEM replacement that bolts right in please?
Thanks to all again.
As far as the coil goes, I still have the original, it was taken out YEARS ago and replaced with the EXCEL I have. I wonder if its still any good? If not, I know I can get a replacement but they don't have the riveted bracket built in. Can anyone suggest a good OEM replacement that bolts right in please?
Thanks to all again.
05-31-2016, 12:05 AM
#16
Re: Code 42, HELP!!!
You'll probably find that most replacement coils will want you to drill the rivets and bolt the original bracket to the new coil. If you dont want to grind on the original coil, I want to say some of the 4.3L trucks used the same coil bracket.
06-03-2016, 05:20 PM
#17
Re: Code 42, HELP!!!
So I installed a DELCO ICM. I started her up, initially the same thing, ran like crap, hesitate and stall. Had to charge the battery again to get her started. Got it running, VERY response but check engine light on, running perfectly otherwise, no hesitation. Shut it down, check codes, yup 42 only again.
Removed ODB tool, started her up, right up, NO LIGHT, running perfectly now but code 42 is still present. I will try and clear the codes again tomorrow. But I drove it around my parking lot and she is running great otherwise. I did notice a rev by itself when I stepped away, then settled back down. I will run a vacuum leak test again tomorrow as well. Will update until fixed.
All the support you guys give is really appreciated. Thanks!
Removed ODB tool, started her up, right up, NO LIGHT, running perfectly now but code 42 is still present. I will try and clear the codes again tomorrow. But I drove it around my parking lot and she is running great otherwise. I did notice a rev by itself when I stepped away, then settled back down. I will run a vacuum leak test again tomorrow as well. Will update until fixed.
All the support you guys give is really appreciated. Thanks!
Last edited by Hawkeye1980; 06-03-2016 at 05:35 PM.
06-06-2016, 09:50 AM
#18
Re: Code 42, HELP!!!
Well she is right back to her old habits, hard to start, when runs, runs like crap and the code 42 it still there. I am awaiting a new DELCO Ing. coil to come in. If that doesn't fix it, I am tossing the towel in and taking it to the dealer. Maybe the ECM or MAS is bad, but at this point I am too tired and too frustrated with this issue. I just want to drive my car. Will continue to update as I work through this BS.
06-06-2016, 01:37 PM
#19
Re: Code 42, HELP!!!
just did another leak test, from multiple entry points. NOTHING. So I put it back together, started it, code shows up, forgot I had the PCV valve unplugged. While running I opened the metal filter can to see if there were any blockage, nothing. I put it back, saw the pcv valve vacuum line off, attatched it. Still had code but running perfectly. Shut it down, disconnected battery for 1 minute. Started her up, PERFECT, no light running like gang busters. Let it sit for 5 minutes running. Came back has code, hesitation.
This is so damn aggravating now. I am going to install the new coil when it arrives. If still the same, will try the carb spray test to see if it revs and still confirms some sort of leak I am not catching. If not then I can only assume its the ECM or the MAS.
Anyone have any thoughts?
Just a reminder, the car starts, runs briefly then dies. I have to do this several times, and then she runs. Give it gas and dies. Once warmed up, running fine, but hesitation when I give it gas, like the air fuel mixture is screwed up. yet there are times when I fiddle with it, she is fine and sounds amazing and no code 42.
This is so damn aggravating now. I am going to install the new coil when it arrives. If still the same, will try the carb spray test to see if it revs and still confirms some sort of leak I am not catching. If not then I can only assume its the ECM or the MAS.
Anyone have any thoughts?
Just a reminder, the car starts, runs briefly then dies. I have to do this several times, and then she runs. Give it gas and dies. Once warmed up, running fine, but hesitation when I give it gas, like the air fuel mixture is screwed up. yet there are times when I fiddle with it, she is fine and sounds amazing and no code 42.
06-08-2016, 03:40 PM
#20
Re: Code 42, HELP!!!
Ok, that's it. I just installed the DELCO coil, reset the ECM. SAME STUPID CODE SAME RUNNING LIKE CRAP. I have had it with this. I just don't get why I cant get this resolved. If I don't get it fix I will sick my tommy gun on it. I just can't deal with it anymore.
Its either I try a new ECM or MAS. At this point I am sure it will not fix the issue. As soon as money frees up, I am taking to the dealer. I am too pissed off right now. Thanks for all the help, this time I am stumped. :/
Its either I try a new ECM or MAS. At this point I am sure it will not fix the issue. As soon as money frees up, I am taking to the dealer. I am too pissed off right now. Thanks for all the help, this time I am stumped. :/
06-08-2016, 08:12 PM
#22
Supreme Member
Re: Code 42, HELP!!!
This might be covering old ground (no pun intended) regarding things you already tried but I'll post it anyway.
Code 42 is set when ever any of these three conditions are met:
1. When the system is running on the ignition module (which means no voltage in the bypass wire) the ignition module grounds the EST wire from the ECM. The ECM expects to see no voltage in the EST wire. If the ECM sees voltage in the EST wire, it sets Code 42. You replaced the ignition module. Probably not the problem.
2. If the bypass wire is open (unplugged or otherwise) or grounded, the ECM will set Code 42.
3. If the EST wire is grounded there is no EST signal. The ECM will set Code 42.
I think there's something sketch with the bypass or EST wires. Take a look at the attached schematics.
Test 1 - This is to make sure there's no opens/grounds in the bypass wire.
1. Unplug the harness at the ECM.
2. Unplug the harness at the ignition module.
3. Set your DVM to "diode" - test beep the leads.
4. Connect the leads (You'll need l-o-n-g wires) to the harness contacts.
5. See if there's continuity (or no continuity) - report back.
6. Re-connect the harness at the ignition module and ECM.
Test 2 - This tests the integrity of the connection within the bypass connector.
1. Clear codes.
2. Unplug the bypass connector.
3. Leave the connector unplugged and securely jumper between the disconnected halves.
4. Start engine.
5. Does Code 42 set? - Report back.
Test 3 - This tests the EST wire for opens/grounds.
1. Repeat Test 1 but on the EST wire - report back.
It would be easier to do Test 3 after Test 1.
Code 42 is set when ever any of these three conditions are met:
1. When the system is running on the ignition module (which means no voltage in the bypass wire) the ignition module grounds the EST wire from the ECM. The ECM expects to see no voltage in the EST wire. If the ECM sees voltage in the EST wire, it sets Code 42. You replaced the ignition module. Probably not the problem.
2. If the bypass wire is open (unplugged or otherwise) or grounded, the ECM will set Code 42.
3. If the EST wire is grounded there is no EST signal. The ECM will set Code 42.
I think there's something sketch with the bypass or EST wires. Take a look at the attached schematics.
Test 1 - This is to make sure there's no opens/grounds in the bypass wire.
1. Unplug the harness at the ECM.
2. Unplug the harness at the ignition module.
3. Set your DVM to "diode" - test beep the leads.
4. Connect the leads (You'll need l-o-n-g wires) to the harness contacts.
5. See if there's continuity (or no continuity) - report back.
6. Re-connect the harness at the ignition module and ECM.
Test 2 - This tests the integrity of the connection within the bypass connector.
1. Clear codes.
2. Unplug the bypass connector.
3. Leave the connector unplugged and securely jumper between the disconnected halves.
4. Start engine.
5. Does Code 42 set? - Report back.
Test 3 - This tests the EST wire for opens/grounds.
1. Repeat Test 1 but on the EST wire - report back.
It would be easier to do Test 3 after Test 1.
06-08-2016, 09:36 PM
#23
Re: Code 42, HELP!!!
This might be covering old ground (no pun intended) regarding things you already tried but I'll post it anyway.
Code 42 is set when ever any of these three conditions are met:
1. When the system is running on the ignition module (which means no voltage in the bypass wire) the ignition module grounds the EST wire from the ECM. The ECM expects to see no voltage in the EST wire. If the ECM sees voltage in the EST wire, it sets Code 42. You replaced the ignition module. Probably not the problem.
2. If the bypass wire is open (unplugged or otherwise) or grounded, the ECM will set Code 42.
3. If the EST wire is grounded there is no EST signal. The ECM will set Code 42.
I think there's something sketch with the bypass or EST wires. Take a look at the attached schematics.
Test 1 - This is to make sure there's no opens/grounds in the bypass wire.
1. Unplug the harness at the ECM.
2. Unplug the harness at the ignition module.
3. Set your DVM to "diode" - test beep the leads.
4. Connect the leads (You'll need l-o-n-g wires) to the harness contacts.
5. See if there's continuity (or no continuity) - report back.
6. Re-connect the harness at the ignition module and ECM.
Test 2 - This tests the integrity of the connection within the bypass connector.
1. Clear codes.
2. Unplug the bypass connector.
3. Leave the connector unplugged and securely jumper between the disconnected halves.
4. Start engine.
5. Does Code 42 set? - Report back.
Test 3 - This tests the EST wire for opens/grounds.
1. Repeat Test 1 but on the EST wire - report back.
It would be easier to do Test 3 after Test 1.
Code 42 is set when ever any of these three conditions are met:
1. When the system is running on the ignition module (which means no voltage in the bypass wire) the ignition module grounds the EST wire from the ECM. The ECM expects to see no voltage in the EST wire. If the ECM sees voltage in the EST wire, it sets Code 42. You replaced the ignition module. Probably not the problem.
2. If the bypass wire is open (unplugged or otherwise) or grounded, the ECM will set Code 42.
3. If the EST wire is grounded there is no EST signal. The ECM will set Code 42.
I think there's something sketch with the bypass or EST wires. Take a look at the attached schematics.
Test 1 - This is to make sure there's no opens/grounds in the bypass wire.
1. Unplug the harness at the ECM.
2. Unplug the harness at the ignition module.
3. Set your DVM to "diode" - test beep the leads.
4. Connect the leads (You'll need l-o-n-g wires) to the harness contacts.
5. See if there's continuity (or no continuity) - report back.
6. Re-connect the harness at the ignition module and ECM.
Test 2 - This tests the integrity of the connection within the bypass connector.
1. Clear codes.
2. Unplug the bypass connector.
3. Leave the connector unplugged and securely jumper between the disconnected halves.
4. Start engine.
5. Does Code 42 set? - Report back.
Test 3 - This tests the EST wire for opens/grounds.
1. Repeat Test 1 but on the EST wire - report back.
It would be easier to do Test 3 after Test 1.
I am going to go over these tests again as you stated . I decided to do the spray test again on the vacuum. I did find the small vacuum tube going to the vacuum storage ball was off and the line is rotted.
Tomorrow I will replace this line as well as do the tests you provided. Again I really appreciate all the help I am getting. Thanks!
06-09-2016, 09:23 AM
#24
Re: Code 42, HELP!!!
Ok, I will report back once I run these tests. However it looks like the vacuum storage ball is gone. I pulled down the plastic cover that attaches to the front fender drivers side, its not there. I cant even determine where it was originally mounted. This is crazy. I have the GM service manual, the original, and its shows the general area where it goes, but in my car, nothing, just an empty unplugged vacuum hose. I do have cruise control so it should be there.
06-09-2016, 02:43 PM
#25
Supreme Member
Re: Code 42, HELP!!!
Venting is OK. We all have to do it. If we didn't, we'd all have ulcers and a lot more objects and people with bullet holes in them.
06-09-2016, 04:51 PM
#27
Member
Join Date: Apr 2014
Location: South of Joliet, IL
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Car: 91 Firebird
Re: Code 42, HELP!!!
The part you showed was for an ignition coil, not an ICM,
Here is an ICM:
http://www.ebay.com/itm/Ignition-Con...FVBUqg&vxp=mtr
This is an ignition control module, also when replacing you should use thermal paste, unless you like replacing it repeatedly.
Here is an ICM:
http://www.ebay.com/itm/Ignition-Con...FVBUqg&vxp=mtr
This is an ignition control module, also when replacing you should use thermal paste, unless you like replacing it repeatedly.
06-09-2016, 09:44 PM
#29
Re: Code 42, HELP!!!
The vacuum reservoir, Sphere of Destiny, etc bolts under the battery tray. Sometimes they mount to a bracket which in turn bolts to the triangle brace between the frame rail and bottom of the tray. But most of the time they bolt right to the bottom of the tray under the battery. Look under the battery, you'll see two divots with round holes. Ignore any holes that are square or directly paired with a square hole, and there won't be too many choices left. The ones the ORB OF POWER uses are about 2" back from the front edge of the tray, one is to the far driver's side by the horns, the other is straight across almost in line with the edge of the battery hold down tab.
Keep after the problem and eventually you'll get it.
Keep after the problem and eventually you'll get it.
06-09-2016, 10:01 PM
#30
Re: Code 42, HELP!!!
The vacuum reservoir, Sphere of Destiny, etc bolts under the battery tray. Sometimes they mount to a bracket which in turn bolts to the triangle brace between the frame rail and bottom of the tray. But most of the time they bolt right to the bottom of the tray under the battery. Look under the battery, you'll see two divots with round holes. Ignore any holes that are square or directly paired with a square hole, and there won't be too many choices left. The ones the ORB OF POWER uses are about 2" back from the front edge of the tray, one is to the far driver's side by the horns, the other is straight across almost in line with the edge of the battery hold down tab.
Keep after the problem and eventually you'll get it.
Keep after the problem and eventually you'll get it.
What gets me is where did the original go? I know my memory is shot butni would have remembered removing it. Just baffles my mind.
06-10-2016, 04:20 PM
#31
Re: Code 42, HELP!!!
This might be covering old ground (no pun intended) regarding things you already tried but I'll post it anyway.
Code 42 is set when ever any of these three conditions are met:
1. When the system is running on the ignition module (which means no voltage in the bypass wire) the ignition module grounds the EST wire from the ECM. The ECM expects to see no voltage in the EST wire. If the ECM sees voltage in the EST wire, it sets Code 42. You replaced the ignition module. Probably not the problem.
2. If the bypass wire is open (unplugged or otherwise) or grounded, the ECM will set Code 42.
3. If the EST wire is grounded there is no EST signal. The ECM will set Code 42.
I think there's something sketch with the bypass or EST wires. Take a look at the attached schematics.
Test 1 - This is to make sure there's no opens/grounds in the bypass wire.
1. Unplug the harness at the ECM.
2. Unplug the harness at the ignition module.
3. Set your DVM to "diode" - test beep the leads.
4. Connect the leads (You'll need l-o-n-g wires) to the harness contacts.
5. See if there's continuity (or no continuity) - report back.
6. Re-connect the harness at the ignition module and ECM.
Test 2 - This tests the integrity of the connection within the bypass connector.
1. Clear codes.
2. Unplug the bypass connector.
3. Leave the connector unplugged and securely jumper between the disconnected halves.
4. Start engine.
5. Does Code 42 set? - Report back.
Test 3 - This tests the EST wire for opens/grounds.
1. Repeat Test 1 but on the EST wire - report back.
It would be easier to do Test 3 after Test 1.
Code 42 is set when ever any of these three conditions are met:
1. When the system is running on the ignition module (which means no voltage in the bypass wire) the ignition module grounds the EST wire from the ECM. The ECM expects to see no voltage in the EST wire. If the ECM sees voltage in the EST wire, it sets Code 42. You replaced the ignition module. Probably not the problem.
2. If the bypass wire is open (unplugged or otherwise) or grounded, the ECM will set Code 42.
3. If the EST wire is grounded there is no EST signal. The ECM will set Code 42.
I think there's something sketch with the bypass or EST wires. Take a look at the attached schematics.
Test 1 - This is to make sure there's no opens/grounds in the bypass wire.
1. Unplug the harness at the ECM.
2. Unplug the harness at the ignition module.
3. Set your DVM to "diode" - test beep the leads.
4. Connect the leads (You'll need l-o-n-g wires) to the harness contacts.
5. See if there's continuity (or no continuity) - report back.
6. Re-connect the harness at the ignition module and ECM.
Test 2 - This tests the integrity of the connection within the bypass connector.
1. Clear codes.
2. Unplug the bypass connector.
3. Leave the connector unplugged and securely jumper between the disconnected halves.
4. Start engine.
5. Does Code 42 set? - Report back.
Test 3 - This tests the EST wire for opens/grounds.
1. Repeat Test 1 but on the EST wire - report back.
It would be easier to do Test 3 after Test 1.
Test 1
Check continuity on Tan/blk line as in your drawing, working perfectly, steady beep
Test 2
Battery disconnected overnight. Ran a jumper on connector for tan/blk wire, start car, code 42 reports again, car starts, runs a bit, dies, do that a few times. Then runs but very low idle near stall, warms up, runs fine, but when I give it gas, it hesitates
Test 3
Same as test 1 on white wire, no issues, working perfectly
Performed test 1 and 3 first, then test 2 last.
Code 14 is gone again, ONLY code 42 reporting.
Looking forward to your follow up.
Also, I had to clamp off the line that goes to the vacuum reservoir. That will be in next week. All the accessory 5/32 lines are now new. I replaced the bigger lines last year and they are fine.
Last edited by Hawkeye1980; 06-10-2016 at 04:24 PM.
06-12-2016, 10:57 AM
#32
Re: Code 42, HELP!!!
Ok here is a follow up. This is driving me NUTS by the way.
I found a website that deals with this on a fiero
http://www.fieros.de/en/v6help/code42.html
I did test both 423 and 424 for continuity, both are reporting FINE, steady beep, move wires around, etc. Examined connectors on both ends, no issues physically either.
So here is the test and how it went:
1. Clear Codes. Idle engine for 1 minute or until code 42 sets. Does code 42 set?
YES NO (YES)
2. Ignition off.
Disconnect ECM connectors.
Ignition on.
Ohmmeter selector switch in the 1000 to 2000 Ohms range.
Probe ECM harness connector CKT 423 with an Ohmmeter to ground.
It should read less than 500 Ohms.
Does it?
YES NO (YES)
3. Probe ECM harness connector CKT 424 with a test light to 12 Volts and note light
Light OFF Light ON (Light OFF)
4. With Ohmmeter still connected to ECM harness CKT 423 and ground. Again probe ECM harness CKT 424 with the test light connected to 12 Volts. (As test light contacts CKT 424, resistance should switch from under 500 to over 5000 Ohms).
Does it?
NO YES (NO)
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (NO)
Result:
CKT 424 open, faulty connections or faulty ignition module. (my ignition module is BRAND new, if it was bad it would not start at all, which it does however I will have it tested at autozone today)
CKT 423 shorted to ground. (IF 423 was grounding out, I should get a beep on the DVM if I touch one side to the 423 and the other to ground, NO BEEP. so HOW can it be grounding out??)
I am still awaiting the delivery of the Vacuum reservoir ball. I ran a smoke test on the accessory vacuum line, no leaks either. I also ran it again on the plenum but I did something different. I left the entire air intake with the MAS attached. The throttle was closed, and I saw some come out around the spring in the plenum where the throttle linkage is. I opened the throttle and nothing shows up, all sealed fine.
When I run the car and shoot starter fluid in that area, its does not affect idle so no leak from what I can tell.
I am trying but not having much luck. Not sure if it is the wiring or the ECM at this point. Will try again once the ball comes in this week. ARRGGGHHHH!!
I found a website that deals with this on a fiero
http://www.fieros.de/en/v6help/code42.html
I did test both 423 and 424 for continuity, both are reporting FINE, steady beep, move wires around, etc. Examined connectors on both ends, no issues physically either.
So here is the test and how it went:
1. Clear Codes. Idle engine for 1 minute or until code 42 sets. Does code 42 set?
YES NO (YES)
2. Ignition off.
Disconnect ECM connectors.
Ignition on.
Ohmmeter selector switch in the 1000 to 2000 Ohms range.
Probe ECM harness connector CKT 423 with an Ohmmeter to ground.
It should read less than 500 Ohms.
Does it?
YES NO (YES)
3. Probe ECM harness connector CKT 424 with a test light to 12 Volts and note light
Light OFF Light ON (Light OFF)
4. With Ohmmeter still connected to ECM harness CKT 423 and ground. Again probe ECM harness CKT 424 with the test light connected to 12 Volts. (As test light contacts CKT 424, resistance should switch from under 500 to over 5000 Ohms).
Does it?
NO YES (NO)
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (NO)
Result:
CKT 424 open, faulty connections or faulty ignition module. (my ignition module is BRAND new, if it was bad it would not start at all, which it does however I will have it tested at autozone today)
CKT 423 shorted to ground. (IF 423 was grounding out, I should get a beep on the DVM if I touch one side to the 423 and the other to ground, NO BEEP. so HOW can it be grounding out??)
I am still awaiting the delivery of the Vacuum reservoir ball. I ran a smoke test on the accessory vacuum line, no leaks either. I also ran it again on the plenum but I did something different. I left the entire air intake with the MAS attached. The throttle was closed, and I saw some come out around the spring in the plenum where the throttle linkage is. I opened the throttle and nothing shows up, all sealed fine.
When I run the car and shoot starter fluid in that area, its does not affect idle so no leak from what I can tell.
I am trying but not having much luck. Not sure if it is the wiring or the ECM at this point. Will try again once the ball comes in this week. ARRGGGHHHH!!
Last edited by Hawkeye1980; 06-12-2016 at 11:03 AM.
06-12-2016, 12:35 PM
#33
Supreme Member
Re: Code 42, HELP!!!
Ok here is a follow up. This is driving me NUTS by the way.
I found a website that deals with this on a fiero
http://www.fieros.de/en/v6help/code42.html
I did test both 423 and 424 for continuity, both are reporting FINE, steady beep, move wires around, etc. Examined connectors on both ends, no issues physically either.
So here is the test and how it went:
1. Clear Codes. Idle engine for 1 minute or until code 42 sets. Does code 42 set?
YES NO (YES)
2. Ignition off.
Disconnect ECM connectors.
Ignition on.
Ohmmeter selector switch in the 1000 to 2000 Ohms range.
Probe ECM harness connector CKT 423 with an Ohmmeter to ground.
It should read less than 500 Ohms.
Does it?
YES NO (YES)
3. Probe ECM harness connector CKT 424 with a test light to 12 Volts and note light
Light OFF Light ON (Light OFF)
4. With Ohmmeter still connected to ECM harness CKT 423 and ground. Again probe ECM harness CKT 424 with the test light connected to 12 Volts. (As test light contacts CKT 424, resistance should switch from under 500 to over 5000 Ohms).
Does it?
NO YES (NO)
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (NO)
Result:
CKT 424 open, faulty connections or faulty ignition module. (my ignition module is BRAND new, if it was bad it would not start at all, which it does however I will have it tested at autozone today)
CKT 423 shorted to ground. (IF 423 was grounding out, I should get a beep on the DVM if I touch one side to the 423 and the other to ground, NO BEEP. so HOW can it be grounding out??)
I am still awaiting the delivery of the Vacuum reservoir ball. I ran a smoke test on the accessory vacuum line, no leaks either. I also ran it again on the plenum but I did something different. I left the entire air intake with the MAS attached. The throttle was closed, and I saw some come out around the spring in the plenum where the throttle linkage is. I opened the throttle and nothing shows up, all sealed fine.
When I run the car and shoot starter fluid in that area, its does not affect idle so no leak from what I can tell.
I am trying but not having much luck. Not sure if it is the wiring or the ECM at this point. Will try again once the ball comes in this week. ARRGGGHHHH!!
I found a website that deals with this on a fiero
http://www.fieros.de/en/v6help/code42.html
I did test both 423 and 424 for continuity, both are reporting FINE, steady beep, move wires around, etc. Examined connectors on both ends, no issues physically either.
So here is the test and how it went:
1. Clear Codes. Idle engine for 1 minute or until code 42 sets. Does code 42 set?
YES NO (YES)
2. Ignition off.
Disconnect ECM connectors.
Ignition on.
Ohmmeter selector switch in the 1000 to 2000 Ohms range.
Probe ECM harness connector CKT 423 with an Ohmmeter to ground.
It should read less than 500 Ohms.
Does it?
YES NO (YES)
3. Probe ECM harness connector CKT 424 with a test light to 12 Volts and note light
Light OFF Light ON (Light OFF)
4. With Ohmmeter still connected to ECM harness CKT 423 and ground. Again probe ECM harness CKT 424 with the test light connected to 12 Volts. (As test light contacts CKT 424, resistance should switch from under 500 to over 5000 Ohms).
Does it?
NO YES (NO)
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (NO)
Result:
CKT 424 open, faulty connections or faulty ignition module. (my ignition module is BRAND new, if it was bad it would not start at all, which it does however I will have it tested at autozone today)
CKT 423 shorted to ground. (IF 423 was grounding out, I should get a beep on the DVM if I touch one side to the 423 and the other to ground, NO BEEP. so HOW can it be grounding out??)
I am still awaiting the delivery of the Vacuum reservoir ball. I ran a smoke test on the accessory vacuum line, no leaks either. I also ran it again on the plenum but I did something different. I left the entire air intake with the MAS attached. The throttle was closed, and I saw some come out around the spring in the plenum where the throttle linkage is. I opened the throttle and nothing shows up, all sealed fine.
When I run the car and shoot starter fluid in that area, its does not affect idle so no leak from what I can tell.
I am trying but not having much luck. Not sure if it is the wiring or the ECM at this point. Will try again once the ball comes in this week. ARRGGGHHHH!!
Step 4 checks the switch circuit inside the ignition module. It's not switching because you're not seeing the resistance in of CKT 423 go from 500 to 5000 ohms.
The failed test at Step 4 indicates that either:
1) CKT 423 is shorted to ground
2) Bypass CKT 424 is open
3) The ignition module or the module connection is bad.
Step 5 determines which of the three things above is at fault. Disconnecting the harness at the ignition module removes it from the test. Because the ohm meter was reading resistance thru the module, disconnecting it essentially opens CKT 423. The ohm meter should read infinite resistance with the connector removed; the ohm meter should read infinite resistance (open circuit) of CKT 423. You reported that it doesn't. Therefore, even with the harness disconnected at the ignition module, it's still grounded someplace.
You're problem is CKT 423 is grounded someplace between the ECM and the ignition module.
I don't understand why you don't get "beeps" from CKT 423 either. Provided you ran the tests exactly as described in the FSM, it still indicates that CKT 423 is grounded.
On a side note, think back hard....did you ever measure resistance of anything in the ignition system with the connectors still attached to the ECM?
06-12-2016, 01:11 PM
#34
Re: Code 42, HELP!!!
You found your problem. You just don't realize it. Re-read the flow chart for Code 42 in the FSM.
Step 4 checks the switch circuit inside the ignition module. It's not switching because you're not seeing the resistance in of CKT 423 go from 500 to 5000 ohms.
The failed test at Step 4 indicates that either:
1) CKT 423 is shorted to ground
2) Bypass CKT 424 is open
3) The ignition module or the module connection is bad.
Step 5 determines which of the three things above is at fault. Disconnecting the harness at the ignition module removes it from the test. Because the ohm meter was reading resistance thru the module, disconnecting it essentially opens CKT 423. The ohm meter should read infinite resistance with the connector removed; the ohm meter should read infinite resistance (open circuit) of CKT 423. You reported that it doesn't. Therefore, even with the harness disconnected at the ignition module, it's still grounded someplace.
You're problem is CKT 423 is grounded someplace between the ECM and the ignition module.
I don't understand why you don't get "beeps" from CKT 423 either. Provided you ran the tests exactly as described in the FSM, it still indicates that CKT 423 is grounded.
On a side note, think back hard....did you ever measure resistance of anything in the ignition system with the connectors still attached to the ECM?
Step 4 checks the switch circuit inside the ignition module. It's not switching because you're not seeing the resistance in of CKT 423 go from 500 to 5000 ohms.
The failed test at Step 4 indicates that either:
1) CKT 423 is shorted to ground
2) Bypass CKT 424 is open
3) The ignition module or the module connection is bad.
Step 5 determines which of the three things above is at fault. Disconnecting the harness at the ignition module removes it from the test. Because the ohm meter was reading resistance thru the module, disconnecting it essentially opens CKT 423. The ohm meter should read infinite resistance with the connector removed; the ohm meter should read infinite resistance (open circuit) of CKT 423. You reported that it doesn't. Therefore, even with the harness disconnected at the ignition module, it's still grounded someplace.
You're problem is CKT 423 is grounded someplace between the ECM and the ignition module.
I don't understand why you don't get "beeps" from CKT 423 either. Provided you ran the tests exactly as described in the FSM, it still indicates that CKT 423 is grounded.
On a side note, think back hard....did you ever measure resistance of anything in the ignition system with the connectors still attached to the ECM?
For the side note, it may have been possible, I don't recall ever doing something like that at all recently. Cant say 100% sure being I had this issue since last summer and had to put it to rest.
The thermal paste was very little on the ICM so I just went out and got some at Radio Shack. I also tried to get the ICM tested but AutoZone did not have the right connectors.
06-12-2016, 01:41 PM
#35
Re: Code 42, HELP!!!
Ok follow up. I checked continuity for ckt 424 tan/blk. From the ICM to the external connector, GOOD. I check it from the other side of the external connector to the ECM connector, GOOD.
I checked continuity again on ckt 423 white wire from ECM connector to ICM connector, GOOD. I checked to see if its grounding out, NOTHING no ground at all from either side. I checked the light test, NO LIGHT on 423. I checked it at the ICM and on the ECM connectors. NOTHING, ignition on.
Seems the issue is the 423 is not getting any power from the ICM, not that it is grounded. So what can that be then?
Issues seems to be at the 423 wire agreed, but its not grounding out at all.
I checked continuity again on ckt 423 white wire from ECM connector to ICM connector, GOOD. I checked to see if its grounding out, NOTHING no ground at all from either side. I checked the light test, NO LIGHT on 423. I checked it at the ICM and on the ECM connectors. NOTHING, ignition on.
Seems the issue is the 423 is not getting any power from the ICM, not that it is grounded. So what can that be then?
Issues seems to be at the 423 wire agreed, but its not grounding out at all.
Last edited by Hawkeye1980; 06-12-2016 at 01:45 PM.
06-12-2016, 02:27 PM
#36
Re: Code 42, HELP!!!
Scratch both replies above.
I re ran the entire test again.
All the same result but number 5 changed:
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (Was NO, NOW YES)
End result now:
CKT 424 open, faulty connections or faulty ignition module ( connectors look fine, ICM new, could not get it tested however)
CKT 423 shorted to ground ( again, I don't see it grounding out anywhere, tested at all connections NO GROUNDING OUT)
I am back to the ICM. I know they are a trouble spot, but man I keep tossing money away. Should I try ANOTHER ONE???
I re ran the entire test again.
All the same result but number 5 changed:
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (Was NO, NOW YES)
End result now:
CKT 424 open, faulty connections or faulty ignition module ( connectors look fine, ICM new, could not get it tested however)
CKT 423 shorted to ground ( again, I don't see it grounding out anywhere, tested at all connections NO GROUNDING OUT)
I am back to the ICM. I know they are a trouble spot, but man I keep tossing money away. Should I try ANOTHER ONE???
06-12-2016, 03:02 PM
#37
Re: Code 42, HELP!!!
Ok so one more time, I reset the codes added thermal past to ICM. No good, 42 again. Going to get that reservoir in. If that does not fix this, to the dealer. I am too fed up wit this stupid issue. Cant believe its the new 60 buck GM ICM I just bought but, I have no way to confirm. If it was bad the car wouldn't even run I would think, which it does. I am at a loss on this.
Will update when the ball comes in.
Will update when the ball comes in.
Last edited by Hawkeye1980; 06-12-2016 at 03:37 PM.
06-12-2016, 05:16 PM
#38
Junior Member
Join Date: May 2016
Location: Staten Island ny
Posts: 3
Likes: 0
Received 0 Likes
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0 Posts
Car: 1989 iroc convertiable
Engine: lb9
Transmission: 700r4
Re: Code 42, HELP!!!
Did you look at and test the pickup coil ? They have a tendancy to rust up and bind the distributer
06-12-2016, 05:37 PM
#39
Re: Code 42, HELP!!!
I was considering the distributor or something within it going bad. I would have to pull it to test it though from what I have seen. Just nothing showing that this part would cause the code 42. Beyond that the tests I did show the ICM being bad or a short in one of the 2 wires. Wires are good, no shorts or grounding and the ICM is brand new.
Its getting to the point I just want it fixed so I can drive it again. Nice weather here in NYS and I cant enjoy it. Thanks for the input and info. I will look into it as well.
06-12-2016, 05:53 PM
#40
Re: Code 42, HELP!!!
Hang on. I just saw something. regarding the test light. I was connecting it to ground and probing ckt 424. If I am re reading this right, I have t connect the alligator clip to +12v and the metal probe to ckt 424 yes? Meaning if the light comes on, 424 is grounded?
I will test this ASAP.
I will test this ASAP.
06-12-2016, 06:12 PM
#41
Re: Code 42, HELP!!!
Sorry gang for all the stupid confusion on my part. I had the test light wrong. So skip above this is the finding now confirmed, again SORRY!!
1. Clear Codes. Idle engine for 1 minute or until code 42 sets. Does code 42 set?
YES NO (YES)
2. Ignition off.
Disconnect ECM connectors.
Ignition on.
Ohmmeter selector switch in the 1000 to 2000 Ohms range.
Probe ECM harness connector CKT 423 with an Ohmmeter to ground.
It should read less than 500 Ohms.
Does it?
YES NO (YES)
3. Probe ECM harness connector CKT 424 with a test light to 12 Volts and note light
Light OFF Light ON (Light on)
4. Disconnect ignition module 4-way connector.
Light OFF Light ON (Light off)
This only matters if light was off in number 3
4. With Ohmmeter still connected to ECM harness CKT 423 and ground. Again probe ECM harness CKT 424 with the test light connected to 12 Volts. (As test light contacts CKT 424, resistance should switch from under 500 to over 5000 Ohms).
Does it?
NO YES (NO)
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (YES)
So after number 3, with the 4 prong connector off the ICM the light does NOT light up. The GM service manual mr. 3in states that this is a faulty ICM. The feiro website agrees and states also it could be ckt 424 is short to ground. Now THAT I tested and it is NOT shorting to ground. So, it has to be a bad new DELCO ICM then? I hope its that simple.
1. Clear Codes. Idle engine for 1 minute or until code 42 sets. Does code 42 set?
YES NO (YES)
2. Ignition off.
Disconnect ECM connectors.
Ignition on.
Ohmmeter selector switch in the 1000 to 2000 Ohms range.
Probe ECM harness connector CKT 423 with an Ohmmeter to ground.
It should read less than 500 Ohms.
Does it?
YES NO (YES)
3. Probe ECM harness connector CKT 424 with a test light to 12 Volts and note light
Light OFF Light ON (Light on)
4. Disconnect ignition module 4-way connector.
Light OFF Light ON (Light off)
This only matters if light was off in number 3
4. With Ohmmeter still connected to ECM harness CKT 423 and ground. Again probe ECM harness CKT 424 with the test light connected to 12 Volts. (As test light contacts CKT 424, resistance should switch from under 500 to over 5000 Ohms).
Does it?
NO YES (NO)
5. Disconnect Distributor 4-way connector. Note Ohmmeter that is still connected to CKT 423 and ground. Resistance should have gone high (open circuit).
Does it?
NO YES (YES)
So after number 3, with the 4 prong connector off the ICM the light does NOT light up. The GM service manual mr. 3in states that this is a faulty ICM. The feiro website agrees and states also it could be ckt 424 is short to ground. Now THAT I tested and it is NOT shorting to ground. So, it has to be a bad new DELCO ICM then? I hope its that simple.
06-12-2016, 06:40 PM
#42
Junior Member
Join Date: May 2016
Location: Staten Island ny
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Car: 1989 iroc convertiable
Engine: lb9
Transmission: 700r4
Re: Code 42, HELP!!!
The ICM recieves its pulse signal from the pickup coil . If the pu is no good the ICM gets nothing to send to Ecm . The computer sets the code because it assumes the line from the ignition system must be open or shorted. If the pickup is rusty and there is orange silt, mark and pull the distributer and try tuning it by hand. If it clicks and binds replace it.
06-12-2016, 07:19 PM
#43
Re: Code 42, HELP!!!
The ICM recieves its pulse signal from the pickup coil . If the pu is no good the ICM gets nothing to send to Ecm . The computer sets the code because it assumes the line from the ignition system must be open or shorted. If the pickup is rusty and there is orange silt, mark and pull the distributer and try tuning it by hand. If it clicks and binds replace it.
Also, if I had to replace it any recommendations on what brand etc? thanks!
06-12-2016, 09:13 PM
#44
Junior Member
Join Date: May 2016
Location: Staten Island ny
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Car: 1989 iroc convertiable
Engine: lb9
Transmission: 700r4
Re: Code 42, HELP!!!
To remove a distributor. First remove label and remove plug wires remove the cap and leave the rotor in place . Mark the base distributor straight down from the tip of the rotor. Pull the dist up slowly noting which way the rotor turns .Mark the dist base where the rotor stops turning.
If you replacing the dist transfer ur marks to the replacement part
To put it back in . Line the rotor tip up to the second mark u made. Slowly lower the distributor back into the motor. As it goes in the rotor should turn right to ur first mark. Put the cap and wire back on . Start the car let it warm up. Set timing as per factory specs. I would use A/C Delco for my car
If you replacing the dist transfer ur marks to the replacement part
To put it back in . Line the rotor tip up to the second mark u made. Slowly lower the distributor back into the motor. As it goes in the rotor should turn right to ur first mark. Put the cap and wire back on . Start the car let it warm up. Set timing as per factory specs. I would use A/C Delco for my car
Last edited by soapy256; 06-12-2016 at 09:17 PM.
06-12-2016, 09:24 PM
#45
Re: Code 42, HELP!!!
To remove a distributor. First remove label and remove plug wires remove the cap and leave the rotor in place . Mark the base distributor straight down from the tip of the rotor. Pull the dist up slowly noting which way the rotor turns .Mark the dist base where the rotor stops turning.
If you replacing the dist transfer ur marks to the replacement part
To put it back in . Line the rotor tip up to the second mark u made. Slowly lower the distributor back into the motor. As it goes in the rotor should turn right to ur first mark. Put the cap and wire back on . Start the car let it warm up. Set timing as per factory specs. I would use A/C Delco for my car
If you replacing the dist transfer ur marks to the replacement part
To put it back in . Line the rotor tip up to the second mark u made. Slowly lower the distributor back into the motor. As it goes in the rotor should turn right to ur first mark. Put the cap and wire back on . Start the car let it warm up. Set timing as per factory specs. I would use A/C Delco for my car
06-13-2016, 07:50 AM
#46
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Car: 91 G92 Z28
Engine: 305 TPI
Transmission: T5
Axle/Gears: 342
Re: Code 42, HELP!!!
Have you tried jumping over the factory wire from the ECM? Just get a length of wire long enough to get around as many of the factory connections as possible, then snip the factory wire and jump around it. You can always solder the factory wire back together if that doesnt fix it, but at least it will rule out that you don't have an intermittent short in there somewhere.
06-13-2016, 08:01 AM
#47
Re: Code 42, HELP!!!
Have you tried jumping over the factory wire from the ECM? Just get a length of wire long enough to get around as many of the factory connections as possible, then snip the factory wire and jump around it. You can always solder the factory wire back together if that doesnt fix it, but at least it will rule out that you don't have an intermittent short in there somewhere.
Later today will try a news icm. If that does not work I am going to pull the distributor and check it. It is over 25 years old. Thanks.
06-13-2016, 02:44 PM
#48
Re: Code 42, HELP!!!
Another Update:
Ok ORB OF POWER, or I like to call it my Death Star showed up. I replaced the ICM with the one from AutoZone as well. Start the car, starts better but stalled 2 times. Got it running, sounds good, up come engine light, and it hesitates with gas given. Check codes, now I get a code 32 AND 42. Reset the computer to clear codes. Start again, just wont start, pumped it and it started, VERY LOW idle, near stall. Shut down and check codes, 32 gone, JUST 42. Clear code again. Starts right up, up comes engine light, hesitates giving gas. Then, the light goes out, car is running PERFECTLY, ho hesitation at all. Shut down and start up 5 times, NO light, runs perfect.
Mind you it did this one time before when replaced other parts. I will continue to start run it and see how it goes. I am tempted to replace the distributor being it is very old.
Anyone have any thoughts on this? I hope she is not teasing me and its ok. GEEZ!!!
Ok ORB OF POWER, or I like to call it my Death Star showed up. I replaced the ICM with the one from AutoZone as well. Start the car, starts better but stalled 2 times. Got it running, sounds good, up come engine light, and it hesitates with gas given. Check codes, now I get a code 32 AND 42. Reset the computer to clear codes. Start again, just wont start, pumped it and it started, VERY LOW idle, near stall. Shut down and check codes, 32 gone, JUST 42. Clear code again. Starts right up, up comes engine light, hesitates giving gas. Then, the light goes out, car is running PERFECTLY, ho hesitation at all. Shut down and start up 5 times, NO light, runs perfect.
Mind you it did this one time before when replaced other parts. I will continue to start run it and see how it goes. I am tempted to replace the distributor being it is very old.
Anyone have any thoughts on this? I hope she is not teasing me and its ok. GEEZ!!!
06-13-2016, 02:53 PM
#49
Supreme Member
Re: Code 42, HELP!!!
Another Update:
Ok ORB OF POWER, or I like to call it my Death Star showed up. I replaced the ICM with the one from AutoZone as well. Start the car, starts better but stalled 2 times. Got it running, sounds good, up come engine light, and it hesitates with gas given. Check codes, now I get a code 32 AND 42. Reset the computer to clear codes. Start again, just wont start, pumped it and it started, VERY LOW idle, near stall. Shut down and check codes, 32 gone, JUST 42. Clear code again. Starts right up, up comes engine light, hesitates giving gas. Then, the light goes out, car is running PERFECTLY, ho hesitation at all. Shut down and start up 5 times, NO light, runs perfect.
Mind you it did this one time before when replaced other parts. I will continue to start run it and see how it goes. I am tempted to replace the distributor being it is very old.
Anyone have any thoughts on this? I hope she is not teasing me and its ok. GEEZ!!!
Ok ORB OF POWER, or I like to call it my Death Star showed up. I replaced the ICM with the one from AutoZone as well. Start the car, starts better but stalled 2 times. Got it running, sounds good, up come engine light, and it hesitates with gas given. Check codes, now I get a code 32 AND 42. Reset the computer to clear codes. Start again, just wont start, pumped it and it started, VERY LOW idle, near stall. Shut down and check codes, 32 gone, JUST 42. Clear code again. Starts right up, up comes engine light, hesitates giving gas. Then, the light goes out, car is running PERFECTLY, ho hesitation at all. Shut down and start up 5 times, NO light, runs perfect.
Mind you it did this one time before when replaced other parts. I will continue to start run it and see how it goes. I am tempted to replace the distributor being it is very old.
Anyone have any thoughts on this? I hope she is not teasing me and its ok. GEEZ!!!
However, if you're no longer getting the Code 42, why mess with it some more by changing the distributor?
It's running. Just drive it until you know the Code 42 is gone. THEN if you still have the urge to mess with it, then mess with it. Otherwise, you're just throwing yourself back into the hole you just got out of.
06-13-2016, 02:58 PM
#50
Re: Code 42, HELP!!!
I fail to see the connection between a vacuum reservoir and an ignition related Code 42. I'm not going to trip over it and neither should you.
However, if you're no longer getting the Code 42, why mess with it some more by changing the distributor?
It's running. Just drive it until you know the Code 42 is gone. THEN if you still have the urge to mess with it, then mess with it. Otherwise, you're just throwing yourself back into the hole you just got out of.
However, if you're no longer getting the Code 42, why mess with it some more by changing the distributor?
It's running. Just drive it until you know the Code 42 is gone. THEN if you still have the urge to mess with it, then mess with it. Otherwise, you're just throwing yourself back into the hole you just got out of.
From what I understand a vacuum leak can cause a code 42 as well. Also I did replace the new DELCO ICM with a new AutoZone ICM as well. Maybe it was the ICM all along. Just got a bad DELCO one.
But because of all this, I guess you can say I will believe its fixed when it does not come back for several days in.
If it does, then I will get a new distributor. Once that is done and if it comes back again, off to the dealer it will go.
At least I know CKT 423 and 424 are not the issue being they are working as GM states they should. Fingers crossed!! Thanks again to everyone. Hope I can move on from this!!
Last edited by Hawkeye1980; 06-13-2016 at 03:08 PM.