95 chevy van. Trans in limp mode and check engine light stays on.

[y5mgisi]

Working on a 95 chevy G30 van with a TBI 350/4l80e. It has two problems that i think may be connected. First, the trans is in limp mode. Has only 2nd and reverse. Also, the check engine light is constantly on. Like it only goes out when you turn the key off. Along with that, when you jumper A-B on the aldl port, the light doesnt flash. Just stays on. Any ideas? Thanks!

 

[dyeager535]

Do you have any GM service manuals? If the light works, but doesn't go off, I suspect (don't have the manual right here) that connections to the ECM are probably the first suspect.

Is that the OBD 1.5, or is it the standard OBD1 we all know and love?

 

[Greg Ducato]

any way you retrieve some codes?

 

[dyeager535]

If the light doesn't blink, something is up with the PCM (ECM, whatever) or the light driver circuit.

Might be able to put a proper scan tool on it to pull the codes, but with the light on constant, whatever codes are thrown are almost certainly secondary to resolving the CEL not working properly. It's failing the initial "bootup" so anything that happens after that is pretty much irrelevant at this point.

I only know true OBD1, if you don't get a code 12 with it, the focus is immediately on the ECM and CEL circuit. Light will stay on constant with a bad (or poorly seated) PROM for instance.

 

[y5mgisi]

So as an update. Changed the ECM and now the CEL works properly and can check codes. Only codes are 12, and an ABS code which i dont remember the number of. But now, the van runs quite poorly. So im wondering if previously, the ECM was bad and put the whole truck into limp mode. With the previous ECM, the van ran well but the trans was in limp mode with only 2nd and reverse and the CEL light was on constantly. Now with the new ECM, it runs bad enough that it cant even be driven around the block to see if the trans shifts now. Hunts for idle and just runs bad and rough over all.

The van had been sitting for about 5 years up until a couple weeks ago. The fuel was drained from the tank and 5 fresh gallons were added. Initially it wouldnt run but it was determined that the pick up in the distributor was bad. Upon replacement it ran just fine with the previous ECM.
So thats where we're at now.

 

[dyeager535]

I'd be looking at fuel pressure, but that's because I had the recent problem lol. No idea when GM finally went to hose in the tank that was ethanol resistant.

Plugs, wires, cap, rotor, all should be inspected. All vacuum lines/TBI base gasket. All underhood electrical connectors.