JunJun

Hi.
After I started the engine, it was running fine for a while but stopped suddenly. The way it stopped was that of an electric problem, not of an fuel related one.
Also, strangely, when I connected Pin A and B of the ALDL connector, the SES lamp didn't flash any error code. (It just flashed one, one, one...) It didn't flash even code 12, and I suspect this means something is wrong with the ECM.
And there is one more strange symptom. When the SES lamp flashed, the relay for the coolant fan turned on and the fan started to rotate. When the SES lamp turned off, the fan also stopped.

Do you have any ideas? Any opinions would be appreciated. Thank you.

305 TPI stock engine, 1992 Camaro.

Komet

What happens when you turn the key now? Engine spins over and does not start? Have you checked all your fuses including the one in the engine bay (perhaps by the battery)? Is the rest of the car getting power?

JunJun

Thank you.
Yes, engine spins over but wouldn't fire. Fuel pump and everything else are working. All the fuses are fine.
It's strange the SES lamp doesn't flash any error code, isn't it. At least it should show Code 12.

Tuned Performance

iTrader: (92)

It sounds like a bad ecm , summit racing isn’t priced to bad

https://www.summitracing.com/parts/aaz-77-7730

JunJun

Thanks for your information.
Do you think the prom is fine? I'm still not sure if this problem is caused by a bad ecm or a bad prom. I heard a prom doesn't go bad so easily, but what do you think?

Tuned Performance

iTrader: (92)

Your right prom doesn’t got bad to often and if it looses data will probably get a code 41 or 51.
I think the ecm will even control fuel pump and do a code 12 without prom. Just a odd thing it won’t do the code 12 I think that built into the ecm
firmware not prom related

JunJun

Thank you for your reply.
Yes, it's really odd the SES doesn't flash code 12. The ecm doesn't seem to recognize at all the connection between Pin A and B. I'll try a new ecm and let you know the result later.

RedLeader289

iTrader: (2)

Have you checked the ignition control module? Given these car's reputation I would think that to be more likely than the ECM. The symptoms line up - suddenly stopped running, cranks and cranks but won't fire.

Tuned Performance

iTrader: (92)

Might also check injector pulse with a noid light . Icm like mentioned shorted injectors or ecm .
checking the basics fuel
pre, spark and injector pulse before you buy anything.

JunJun

Thank you. Yes, the ignition control module failure can cause such symptoms, but that doesn't explain why an error code cannot be read including Code 12. Obviously the way the SES flashes is odd... The ecm doesn't recognize the connection between Pin A and Pin B (Nothing happens). Also, the main coolant fan starts to rotate right after the ignition is on, and stops when the SES flashes, and starts to rotate again when the SES goes out... The main coolant fan is controlled by the ecm, isn't it. If there were no such strange symptoms, I would also doubt ignition related parts.

JunJun

Thank you. By the way, what do you mean by 'Icm like mentioned shorted injectors or ecm'?

Tuned Performance

iTrader: (92)

Hate to say through parts at it but it sounds like a ecm replacement is a good choice at this point. Icm was mentioned post above mine just to check basics but the lack of code 12 seems to be ecm

JunJun

Thank you guys, a new ecm has solved the problem!

I think the key was that any error code, including Code 12, could not be retrieved even with the proper prodecure. An odd symptom such that the SES lamp and the main coolant fan relay synchronize also helped me. It was not a simple "the engine won't run" symptom after all. I hope this will help someone in a similar situation.

tom3

Thanks for the update. Good info for future searches!