Check engine light?

[Bigboom997]

My 1990 k2500 is getting a check engine light when I turn it to acc. I put a paper clip in and it comes back with code 12 which from my understanding means nothing's wrong. But when I start up the truck and put the paper clip in I get a flashing check engine light which from my understanding indicates a misfire. Anyone have experience with this that can help me find the cause of my check engine light?

 

[someotherguy]

ACC is turning the key backwards towards you instead of towards "start", is that what you mean? This is just for running the radio; you shouldn't be seeing a CEL. I'm guessing though what you mean is when you turn the key forward like normal, just not far enough to start. Multiple lamps should come on in the cluster at this point, it's just the bulb check. It's normal to see the CEL come on at that point; it's just letting you know the bulb is good.

Flashing check engine light with engine running = misfire, when you *don't* have A&B jumped. Take the paper clip out.

There's probably nothing wrong at all other than a simple misunderstanding of how to check codes. You check them with A&B jumpered and the key on, but the engine NOT running.

Richard

 

[PlayingWithTBI]

^^^X2
When you turn the key on the CEL/SES light should flash 3 times (maybe 2) and then stay on steady. That tells you the ECM is working properly.

With KOEO and A-B jumpered it'll flash 1 then 2 (for 12), then it'll flash other times if you have a MALF Code stored, then it'll flash 12 again at the end of the routine.