DFI and ECMDiscuss all aspects of DFI (Digital Fuel Injection), ECMs (Electronic Control Module), scanners, and diagnostic equipment. Fine tune your Third Gen computer system for top performance.
Welcome to ThirdGen.org!
Welcome to ThirdGen.org.
You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join the ThirdGen.org community today!
Hello, I have a 85 iroc z camaro with a 305. I have the engine light on and so I bought the ECM tester. I got the codes 12, 33, and 34 when I tried it. I'm not quite sure what code 12 does, but code 33 and 34 indicate that my MAP and MAF sensors are working up? What does this mean exactly? I know my idle can be kind of weird and sometimes it takes a couple tries to start but what can I do to fix this? Just replace the sensor? Correct me if anything I said is wrong
This ad is not displayed to registered members. Register your free account today and become a member on ThirdGen!
Sponsored Links
Registered users do not see this ad. Click here to register for free!
code 12 from what people have told me and from experiance is a basic code for when the check engine light is on. the other codes depend on the engine but u can go to chevythunder.com and it will give u a list of the codes and possible problems
Some vehicles equipped with 5.0L or 5.7L port fuel injected engines may experience "Service Engine Soon" light with some combination of codes 33, 34 and/or 36 stored. This bulletin summarizes diagnostic procedures to be used in trouble shooting these codes.
All 1986 model year vehicles should be updated to the latest service PROM per bulletins: 86-162, section 6E Corvette or 86-194, section 6E, Camaro and checked for "Service Engine Soon" light reset prior to further diagnosis. In the case of 1986-87 Camaro or 1986 Corvette the MAF power relay should be checked to assure that it is part number 10067925. If it is not, then it should be replaced with part number 10067925. Please do not substitute.
Diagnosis
CODE 33 (MAF SENSOR VOLTAGE HIGH)
1.Inspect to determine that part number 10067925 relay has not inadvertently been installed as a burnoff relay or incorrectly connected as a burnoff relay.
NOTICE:SOME SERVICE PARTS BOOKS REFLECT THIS INCORRECT USAGE.
For proper relay parts usages, please refer to the relay usage chart provided at the end of this bulletin. No substitutions should be made. 2.With the engine fully warmed up and operating in closed loop, check the airflow at 2000 RPM in neutral using a Tech 1 or equivalent scanner capable of testing air flow. If it is below 16.0 gm/sec for a 5.0L or below 10.0 gm/sec for a 5.7L engine and the block learn value is greater than 130, replace the MAF sensor.
If code 33 still resets, refer to section 6E of the appropriate service manual for further diagnostics.
CODE 34 (MAF SENSOR VOLTAGE LOW)
1.Inspect the plenum side of the throttle blades for deposits. If even a small amount of deposits are present, clean the throttle body
2.Thoroughly inspect the vehicle for sources of air entering the engine without passing through the MAF sensor. Specifically, look for a cracked, cut or loose duct between the air meter and the throttle body, poor inlet runner to plenum or manifold sealing, a split PCV hose or any type of vacuum leak. A large quantity of air does not necessarily have to be involved. If any leaks are found, repair the condition, clear the codes and check if the code resets.
3.Check resistance of the MAF power relay contacts. The resistance should be less than 1 ohm across closed contacts. If the resistance is greater than 1 ohm replace the relay.
4.Check the minimum air rate and compare to specifications found in bulletin 87-100, section 6E. If the air rate is below specifications, please reset by connecting a vacuum gauge to port A on the throttle body, increasing the air rate by turning the minimum air screw until one inch of vacuum appears on the gauge and then reducing the minimum air setting by one half turn of the screw.
If code 34 still resets, refer to section 6E of the appropriate service manual for further diagnostics.
CODE 36 (MAF BURNOFF)
1.Inspect to verify that the MAF power and burnoff relays currently on the vehicle agree with the usage chart provided at the end of this bulletin.
2.Check the relays for proper function per bulletin 87-99, section 6E. Also check for PCV plugged condition per the same bulletin.
3.Check all electrical connections carefully.If code 36 still resets, refer to section 6E of the appropriate service manual for further diagnostics.
RELAY USAGE CHART
YEAR MODEL POWER RELAY BURNOFF RELAY
86 Corvette 10067925 10094701
86-87 Camaro 10067925 10094701
87 Corvette 14089936 14089936
TPI 85-87 Power Relay: 10067925
Burnoff Relay: 10094701
Start with these two relays and replace them! Your relays are old.....and new ones at the dealer are cheap! And TRY to get AC Delco relays, do not get Japan(White Box) Crap!!!
Code 12 is totally normal, it means no signal from the distributor. It comes from when you go to start the car, and you turn the key to the "on" position. At this point, the ECM is on, but the engine is not yet running, and the distributor is not yet rotating. This is the reason the check engine light comes on when you turn the key to "on" without the engine running.
__________________ North Texas Third Gen Association 1988 GTA 5.0/M5/3.45 LSD, T-Tops, Digital Dash, Leather - Current Ride 1983 Firebird S/E - Stripped 1995 Chevy 1500 5.7 Ext. Cab - Daily Driver
correct, you do not have a map sensor. and replacing the burn off relay will assure your maf sensor is cleaning its self between start ups, unless you have wiring issues. and idk if you will have to replace the sensor, there are flow charts of diagnosing whether it needs replaced or not, and the tpi swapper's guide book has that. but i swapped out my maf and i still had the intermittent problem. so idk. i know im going to try the new burn off relay and see how it is sometime in the next week or so. if that doesnt fix it, ill buy the swappers guide and get down to business lol
Okay so I think I understand what to do but first, I have one question! Does this mean my car does not have a MAP sensor?
Wait hold on so what will replacing the power relay and burnoff relay do? Will I need to replace the sensor anyways?
YOU DO NOT HAVE MAP(Manifold Air Pressure) sensor! MAP sensor came on 3rd gens around 90 or 91 and up. Newer cars are now going back to the MAF sensor. MAF(Mass Air Flow).
Replacing relays will do what?:
1) Burnoff relay: if your burnoff relay fails, your MAF sensor will end up getting too dirty to work properly, and therefore will give ECM wrong readings.
2) MAF Power relay: if this relay fails or is going bad, it can cause the MAF sensor to send incorrect reading/measurments to the ECM. And therefore COULD cause a No Start problem....
3) If either of these relays fail, it could trick the ECM and give you codes that would suggest to replace the MAF sensor, eventhough there is nothing wrong with the MAF sensor itself....
Quick test: Take your burnoff relay and switch it with the fuel pump relay. When you turn your key to On, and the fuel pump Does prime.....relay is most likely GOOD.
Now you can cheat and buy the MAF Power relay first and save some $$$ instead of guessing which to buy first.
Okay I just ordered the power relay and the burnoff relay and they will get here tomorrow. The thing is that I cannot locate them on my car... I tried looking through my Chilton but I can't find them. Can someone post a picture of where they are exactly?
Okay I just ordered the power relay and the burnoff relay and they will get here tomorrow. The thing is that I cannot locate them on my car... I tried looking through my Chilton but I can't find them. Can someone post a picture of where they are exactly?
Check the ECM for the burn off module. It contains both the power and burnoff relays. The ECM is located on the passenger side under the dash. Above where the passenger feet would be.
Silver box attached to the ECM is the burnoff module. Relays will be inside. Although I don't know if they are individually replaceable.
Okay I just ordered the power relay and the burnoff relay and they will get here tomorrow. The thing is that I cannot locate them on my car... I tried looking through my Chilton but I can't find them. Can someone post a picture of where they are exactly?
When you get your new relays, look at your firewall between your brake booster and fender for the OLD relays there. Your new relays look exactly the same as the old ones! and there are NO other relays that look like them there. Double check by looking up part #'s.
With all due respect to the moderator, I don't understand What you are talking about(pic of ECM....Why?). ME of Course has a 85 iroc-z, his relay setup should be the same as my 87 GTA, and my relays are found under the hood!
Last edited by y84pauloflondon; 10-30-2009 at 01:21 AM.
***Note that 2 of 3 relays are round in shape, And I don't know why that is! My org relay and my AC Delco replacments Are the BOX shape type, just like the first relay.***
Last edited by y84pauloflondon; 10-29-2009 at 09:04 PM.
With all due respect to the moderator, I don't understand What you are talking about(pic of ECM....Why?). ME of Course has a 85 iroc-z, his relay setup should be the same as my 87 GTA, and my relays are found under the hood!
The '85 TPI set ups use a different ECM then the '86-'89 TPIs. And the relay set up is also different. Here is a picture of the ECM & burnoff module in an '85 Camaro:
Okay well I got the two relays but I don't know exactly where to put them. On the driver's side I only have my fuel pump relay. Where are the burnoff and power relays located?
Also I checked my fuel pump relay and there is grease all over the inside! Is this normal?!
Okay I looked all over and I can not find anything that looks like a burnoff relay or a power relay. Do you think maybe it's somewhere else in the 85's?
The '85 TPI set ups use a different ECM then the '86-'89 TPIs. And the relay set up is also different. Here is a picture of the ECM & burnoff module in an '85 Camaro:
Oh so they're right on the ecu? Where is the ecu on my car?
And I have another problem now. Since I unplugged and replugged the fuel pump relay my car turned off while driving. I think it's because of the grease around the relay pins. Can I temporarily use the burnoff relay as it will fit?
Check the ECM for the burn off module. It contains both the power and burnoff relays. The ECM is located on the passenger side under the dash. Above where the passenger feet would be.
Silver box attached to the ECM is the burnoff module. Relays will be inside. Although I don't know if they are individually replaceable.
thx for the info. when i plug in the power harness into my maf sensor the car runs like crap. without the harness it runs great all wires and relays check good including voltage. getting desparate need answers thx
thx for the info. when i plug the pwoer wire harness into my MAF the car runs like crap. when i disconnet it the car runs great. all realys and voltage are good. need some help its frustrating. i have a 1988 trana am with a 305. much thx or ur help.
sorry new at this forum stuff. also i bought a new MAF power relay for my car. still does the same thing. i wonder if it could be the ECM itself. not sure. everything checks out per the manual. but i am missing something. much thx for ur help.
lol like i said, NOT cheap. although that price beats the hell out of the boshe price, which i think is between $300-400
LOL, $300-400 Really!!! Are talking about org. BOSCH MAF sensor(new)prt#14084712, stright from GM?....try $1700.00+!!!! Remember, 3rd gens using the MAF sensors were from 85-89, which are now considered Classic Cars....Therefore Classic Parts Prices, which are found in their Classic Car Parts Warehouse!
6 yrs ago I bought a NEW BOSCH maf sensor for my 87 GTA. At the time GM dealers were asking $700 + tax. This past summer, they are now priced at $1965.00 + tax......
BTW cIaRmOaCrZo, that's some really good info on your post #5. Where did you find it?
Last edited by y84pauloflondon; 11-03-2009 at 11:34 PM.
LOL, $300-400 Really!!! Are talking about org. BOSCH MAF sensor(new)prt#14084712, stright from GM?....try $1700.00+!!!! Remember, 3rd gens using the MAF sensors were from 85-89, which are now considered Classic Cars....Therefore Classic Parts Prices, which are found in their Classic Car Parts Warehouse!
6 yrs ago I bought a NEW BOSCH maf sensor for my 87 GTA. At the time GM dealers were asking $700 + tax. This past summer, they are now priced at $1965.00 + tax......
BTW cIaRmOaCrZo, that's some really good info on your post #5. Where did you find it?
HOLLY CRAPPP, i didnt know they were THAT much. wow. lol. and the info came from alldata. the technical service bulletins.
[quote=dirtyd6669;4335596]i also have code 33 and could a bad knock sensor be causeing the code[/quote
may be wrong, but no. actually it kind of depends on what year and engine your car is. but code 33 is maf sensor code,OR (depending on the car) it can be a map code. knock sensor codes range from 41 to i think 43.
Dont know. When i hook up my MAF the cars runs like crap, doesnt idle right, wants to die, step on the gas and it is slow to reving up. So when i disconnect the MAF the car runs fine. This is the third MAF in 4 months that i replaced. I checked all the relays and the wiring and everything is good. So I dont no what to dio next. Any suggestions?
Much thx for your help.
Scotty
Dont know. When i hook up my MAF the cars runs like crap, doesnt idle right, wants to die, step on the gas and it is slow to reving up. So when i disconnect the MAF the car runs fine. This is the third MAF in 4 months that i replaced. I checked all the relays and the wiring and everything is good. So I dont no what to dio next. Any suggestions?
Much thx for your help.
Scotty
so you have been through 3 of em in 4 months, damn thats gotta be expensive. but each time when you replaced it, did run okay?? at least for a while?
Also when my car starts to overheat it shuts down and wont start until it cools down enough to start and run. Reaplaced the thermostat but still has issues.
hey thx for the hepl. The other problem i am having when the car gets hot it dies and doesnt want to start until it cools down enough then it starts and goes. i replaced the thermostat and still has the same issues. Much thx again for your help.
Scotty
