Hi Guys, Im having a problem but maybe someone can point me in the right direction.
I have a check engine light that comes on after about 10 minutes of driving, two shops have scanned my 1991 Firebird 3.1l auto both say the data link is not communicating.
I called the local E.C.M rebuilder (python injectors,Stanton,CA) they said data link problem likely a fuse, light is likely due to "spider cracks in P.C.M". that open up after warm up.
the car failed smog test yesterday HC and Co2 levels @ 10time allowable.

Question has anyone else run into these problems and did rebuilding ecm alone take care of it?

 

Hey there. A couple things come to mind. First off the ecm is under the dash on the passanger side, so heat usually is not an issue (unless the unit heats up itself). If the SES comes on after 10 minutes, it may be once it enters in closed loop. I would think it could be an O2 sensor by the way you failed your smog test. But that is just a guess.

To pull a code manually from the ecm, with the ignition off, get a piece of wire and jump pins A and B on the ALDL connector. Turn the ignition to the on position(do not start it), This will begin flashing the SES light. The first code that will appear is code 12 (one flash, pause, two flashes). This code is normal as it is the diagnostic for the dizzy. Take note of what codes follow by the flashes (ex. code 33 would be 3 flashes, pause, 3 flashes) etc... The codes will then loop until you turn the key off or pull the wire. This should give you a good indication of where to start. Post back if you have any issues.

 

Thank you for the reply hrspwr. I had taken it to two shops both put scanners on it they said the ecm is not communicating, i put a oxygen sensor on it about a year ago, but its possible its bad, the car had a idle problem, I am considering just replacing the MAP, TPS, and Idle air control valve, but hate to waste the money if it is not the problem. I will try the manual code retrieval in the morning see if it works where scanners failed

 

I would not throw money at it quite yet. Get the codes and see what turns up. I know my ecm in my car did not communicate either. I had to swap the ecm in order to communicate with it. Even though the ecm does not communicate with a scanner, you can still retrieve the codes.

 

All you need to read your car's codes, is a paper clip. No "scanner" is necessary.

https://www.thirdgen.org/service-eng...ht-error-codes