For a while now, my check engine light is always on. When I turn the ignition to on, the light comes on and stays lite instead of flashing like I read it is suppose to and I'm unable to pull any codes from the ECM though the ALDL.

I've checked both the dash fuse and checked in the engine compartment for a fuse but I can't find one by traceing the ECM pigtail from the batery. I have also tried replaceing the ECM with a unit from a boneyard but that one may be faulty as well.

If I completely unplug the ECM, the light still stays on. The light should go out when I do this right?

It sounds like a short to me, but I have no idea where to check. If the light is shorting out, would I still be able to use a scan tool to check the ECM? Also what do you recommend as an inexpensive scan tool to get?

Anybody have a wireing diagram for a 1225500 ECM in an 82 Firebird with a LG4?

 

When the ignition switch is first turned to the RUN position, the lamp should turn on for about 1/2 second, flash to off for about 1/10 second, then turn back on and remain on until the engine is running. The flash occurs very quickly, and can be difficult to detect. Check again to be certain that your lamp is operating like that or not.

As for retrieving error codes, even if the lamp is malfunctioning, you should be able to retrieve codes via the ALDL connector. You can use either a separate test lamp, or voltmeter connected to a 12VDC+ source and the 'D' terminal to simulate the lamp. (This is the only way to get codes from some older Ford EEC systems). Once your meter is connected, jumper the diagnostic request line at the ALDL and watch your meter or test lamp just like you would the dash lamp.



Is the engine running normally otherwise?