First off let me start off by saying my mechanical skills greatly out way my computer skills. That being said, I'm more than willing to learn from the wealth of knowledge on this forum. Now, for some back story. The Opti was replaced several times during the previous owners 10 years of ownership. the replacements were done at the GM dealership where the service manager was a friend and fellow member of the local Corvette club. They evidently were getting bad rebuilds or poor quality aftermarket parts as they had to change them out 3 times to get the car to run properly according to the invoices. The last replacement was done in 2017 and the car only has 2000 miles since that replacement. Not saying it hasn't failed again. The car has 46K on the odometer.
So, I bought a Snap ON MT 2500 shortly after I bought the car and used it to get to where I am now. I do have the FSM and have looked at the flow chart diagnostics and see where I need to proceed. My questions are regarding what to replace the Opti with if indeed it is bad and if I may be dealing with a bad ECM? The scanner shows that I have faults on Quad Drivers 2&3 in addition to the code 42.
I have read on here that the ECM's on 92's are problematic so just trying to get all the input I can before proceeding. The car lives a sheltered life and hasn't seen any moisture that could have effected the Opti. Any input will be will be appreciated

Any help will be greatly appreciated

 

Sorry to hear. This.
This one long drawn out No spark.
46k original mileage? To date in 2022

No guarantee on electronics. But a genuine opti failing under 46k is simply not common.

The original owner we assume 1992
10 years approx 2002
2002/3 - 2016 who owned?

*** The dealership replaced the "original opti" at what mileage? And year?

Last opti replaced 2017 makes sense for fail rates due to "knock off" inferior parts/ builds. hence fail rate is common. Within months.

Current code 42 i believe is more common with your ECM failing.

 

The person I bought it from was the 2nd owner. He had the Opti replaced the 1st time in 2015 at 43312 miles. I'm guessing that was the 1st time but no way to know for sure. I have several invoices from him when he had it into the dealer for problems with that replacement. They used 2 remans that were faulty and finally went to an outside aftermarket one. Then I have an invoice from 2017 for another replacement so It looks like it's on it's 4th Opti!!! The car hasn't been driven in the rain or had the engine washed during that time so I doubt it's a moisture issue. Is there any way that a faulty ECM could cause the Opti to fail? That's why I'm thinking I could have something else going on here besides the Opti.

 

Looks like I'm a bit confused and not thinking straight. Wouldn't be the first time I guess that I was thinking that the coil was internal to the Opti. My bad. after going back and rereading the FSM I see that it is either my coil driver/wiring or the ECM. Which do you think is more likely? Also can you shed any light on the Quad driver fault reading that my scanner is showing? My build date is 04/09/92

 

The car is in my shop about 20 minutes away so not readily at hand. When I get back to it I will be clearing the code and checking to see if the code returns. I'm thinking that I do have a problem with the ECM as I occasionally have the fan come on for no reason IE: cold engine and hvac set to off. Thanks for the info on what the quad driver does as I hadn't found anything as to what their purpose was in my searches. Do you recommend getting mine rebuilt or try to find a good used ECM?

 

So I was able to get back to it today. I cleared the code and it came back. I went to step 2 and didn't get a voltage reading. I was using my old analog voltmeter and I'm not sure if I got everything set up properly but I tried it several times and didn't get any reading or movement at all on the meter. By the time I got to step 3 I was getting kind of tired and decided to call it a day as my old brain was starting to get a bit foggy from lack of lunch. I was able to systems check with the MT 2500 and was able to turn the fans on with that. I'm guessing that would be the same as jumping the terminals? Also, Having a hard time figuring out which ECM connector is A that it refers to in step 3. I know there must be something in the FSM but haven't run across it yet. The page it references in the index has them listed as J1 thru 4.

 

Found this to be most fitting as some of the pinouts can be year specific.

 

The ECM has 4 connectors from the harness on mine. I can't figure out which is the one they are referencing to do the next step in diagnosis.

 

Sorry misread...should be in your FSM. I linked pics in another thread...let me see if I can find it...

Those connectors are color coded and the FSM has the color found on similar page...

This is for 1990 but you should similar page in FSM.

If I find one for a 1992...I'll update this post.

 

I have a 1992 as well and was having intermittent issues including a code 42. My issue was cold solder joints in the ECM, a known issue. I sent it to SIA Electronics for repair and it runs great with no codes now.

 

That's been my hunch all along but don't want to just start throwing parts/repairs at it until I've convinced myself/verified that is what is going on. I know there is a lot of different reviews on here as to the quality of SIA's work but I seem to see as many positive as negative so we shall see. I am doing some searches on other businesses but have yet to come across one that offers SIA's lifetime warranty for whatever that is worth.

 

So I believe I've narrowed it down to the ECM after going through all of the tests in the FSM. I believe I need to remove the prom before sending it in for a rebuild. My problem is I can't get it to come out of the ECM. This is my first time dealing with the ECM and I don't want to get too carried away and break something as I realize the 92/93 ECM's aren't exactly plentiful. Is there a secret to getting it to come out without damaging it?

 

Is it the PROM or ECM you cannot remove? The connectors on the ECM are snug and latch in place. For the PROM you remove the screws on the small cover and release a latch on each of the 2 sides and it comes right out.

 

It's the latches on the prom that I'm having a problem with. I can't tell if I need to squeeze them in or pry them out to release them. I've tried doing both gently but haven't had any luck.

 

Pry them out and down and the PROM pops up.

 

That worked. Thanks a lot. I was really apprehensive about putting much force on it without knowing which way they released. I appreciate your help. Now to get it sent off and see if it takes care of my no start and other issues. I've had an issue of the fans coming on for no reason and I'm thinking it's related to the bad ECM.

 

You're welcome! I also had my fans come on randomly until the ECM was repaired.

 

So I got my ECM back from SIA and was all happy about maybe getting the 92 back on the road before the weather goes to hell. Got it back in and nothing. Or, I should say now I have 41 and 42 codes and still no start. I would hate to think that I got a bad repair but I guess that is possible. I'm kind of out of options here. Any suggestions would be appreciated. Am I missing something here or are my diagnostic skills as bad as I'm beginning to think? I've gone through the FSM steps numerous times and have no idea where to look next. SIA said they reflowed it and replaced the quad drivers.

ANY SUGGESTIONS?

 

I wish you were close to me and then I could lend you an ECM for testing.

 

I appreciate your offer even if it's not logistically possible. I spent hours today looking at different posts on here and searching the net to see what I could come up with. Got a few ideas that I'm going to pursue tomorrow. We shall see. I refuse to let this beat me and intend to keep at it until it gets fixed. I love the car and I guess I'll just label it a "Labor of Love"