My 92 RS project is giving a Code 42. I replaced the ESC module under the distributor cap and im still getting a Code 42. Any suggestions?

 

The module at the base of the distributor should be the HEI module (high-energy ignition) and it only performs the switching of the ignition coil primary based on signals from the ECM, as well as reporting reference pulses back to the ECM and tachometer. It would be good to verify the replacement was the correct type/part number.

Does your '92 have a 1228746 ECM? I ask only because there may or may not be a separate EST module mounted to the firewall. If not, it is integrated onto the MEMCAL plugged into the ECM.

In any case, it would be good to inspect all electrical connections in the system, from the distributor to the ECM, including grounds, and also verify the function of the knock sensor. The knock sensor can actually be nulled out for testing by bypassing it with a resistor to ground, with a value of around 3,900Ω (3.9K) temporarily. That would remove one wildcard from the diagnostic tree.

 

The esc is on the bracket by the fuel pump relay. How have you determined it’s faulty ?
The code 42 is related to est, bad ecm or icm or wiring from icm to ecm.

 

should be 100k ohms on tbi ?

 

You're probably correct. I was thinking '730 ECM initially, being a '92 model year, then caught on that it is TBI.

The resistance should be sufficient to load the input just a little and make the ESC/ECM happy should solve the knock sensor temporarily, but I believe the probability is that the problem is not the KS.

 

I think tpi maf and tbi is 100k ks sd tpi 730 and 727 is 3.9k ks ohms

 

Did this Code 42 come up after you tried setting the base timing or after you started fooling with removing the the rest of the Secondary Air Injection Reaction system after the previous owner removed the SMOG pump?

Did the car has this Code 42 since the day you got it?

I ask about the setting of base timing because if you were fooling with that and forgot to reconnect the Set Timing Connector before starting the car it will throw a Code 42. Hell it might even do it without clearing the codes after setting the base timing even if you did reconnect the Set Timing Connector.

I ask about messing with removing the rest of the A.I.R system under hood because you will be in the general area of wiring and connectors related to the Electronic Spark Timing system.

How do we know this is a real Code 42 and not an intermittent or false Code 42? Make sure the Set Timing Connector is connected then disconnect the negative battery cable for 10+ seconds (you can leave it disconnected a minute or so if it makes you feel better) and reconnect the negative battery cable and start the car and let it run for awhile to see if it comes back. If it doesn't take the car out for a road test to see if it comes back.

If Code 42 comes back we will go from there.

 

I've had the code 42 since I got the car. It also have a code 32 and 33 which I have fixed. I have checked all the wiring behind the air cleaner and around the distributor. I disconnected the battery yesterday and let it sit for about 20 minutes. Reconnected and started the car up. It idled high and then stumbled. It did this three times and then idled normally. The check engine light came on immediately. Took it for a ride and the check engine light never went off. The motor never stumbled or tried to shut off during the drive.

 

So it now runs relatively normally, but with a SES lamp lit, correct? And the 42 has been an issue since you got the car?

The initial stumble on startup could have been the ECM re-learning the IAC steps, mixture, O² sensor, and other inputs. It still stands that the ECM is seeing something it does not like in the ESC system.

Stepping back a bit, are you confident that the ECM is original? More importantly, is the CALPAK the original/correct unit for the car? I've been down that path a couple of times on vehicles that were "repaired" by someone else who was assured by the person at the salvage yard counter that the parts were correct for the car. A couple of early '90s TBI trucks really challenged my patience that way in the past.

Another potentially useful step would be to connect a scanner to retrieve live data, and analyze that compared to what should be present.

 

I cannot confirm that the ECM or chip are original to the car. I think I still have the factory chip from my 91 RS. I have also considered replacing the ECM.

 

Do you still have your 1991 Camaro RS?

If you do swap the 92 memcal into the 91 ECM and try that in the 92 before buying a reman ECM for the 92.

Having known good tested parts to swap is nice before wasting money on replacement parts you might not need.

 

Agreed. I was curious if you knew whether the ECM had been changed. If you drop the ECM to clean and reseat the connectors, it would be really easy to pop the cover and see what CALPAk was installed. Looking up the BC code of the PROM could be very revealing.

 

Yes, I do. I will try that this weekend. Thanks gentlemen!

 

I'm going to upload some pictures I took late yesterday evening from my Snap-on MTG2500 Scanner from the Fast-Track Troubleshooter section Code Tips for Code 42.

Check back in this reply and other replies below for updates as I will edit them as I add more info.

Attachments at the bottom of this reply.

I added the refenced sections from the Fast-Track Troubleshooter User's Manual.

G072 is general information and the factory service manual is needed for specific information about your car.

I added the relevant sections from the factory service manual for a 1991 Camaro with a L03 5.0L TBI Engine VIN (E).

 

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If it’s a bad ecm, Rockauto has this and can find a discount code on tgo for checkout

 

@Tuned Performance If by any chance you have the factory service manual for a 1991/1992 Camaro/Firebird could you upload the same sections in it as I have in my first post with the pictures? It's the 2 attached PDF files at the bottom of the list from the 1988 Firebird service manual..

The reason I ask is a 1988 TBI F-Body uses a 8063 ECM and the 1989+ TBI F-Body uses a 8746 ECM.

Thanks.

Also if anyone else has them to upload that would be great too.

 

I don’t have anything in pdf , I have a hardbound I’ll have to find and post the code troubleshooting tree.

 

Well, I don’t have a solid check engine light. It only flickers dimly.

 

Below is the Factory Service Manual for the 1991 Chevrolet Camaro. It's a 2091 page long PDF document.

There are some changes from 1991 to 1992 F-body cars with late 1991.5 F-body cars being closer to 1992 F-body cars. None of these differences affect what you are working on though.

1991-CHEVROLET-CAMARO-SERVICE-MANUAL.pdf

Attached below are the relevant sections that replace the ones I had posted in my reply above from the 1988 Firebird Factory Service Manual. I will delete and replace those attachments in my previous reply with the ones in this reply.

 

 

I owe you a beverage - Your photo reminded me that I hadn't used my Emtpy-2500 lately, and that I should check the backup battery. My suspicion was right, and you saved me a lot of cleanup. As you can see, I also have the more ancient, Dim-Wit, I mean, dimly-lit version with no backlight. The cartridges still apply,