OK - getting codes, CHECK ENGINE light works, but it's not on!

[volvodefector79]

Any ideas? My check engine light now WORKS, as I replaced the burnt out bulb and it activates when starting. It turn off, however, and does not come on.

Here's the tricky part. Some of the time - NOT all of the time - the idle will be poor, like it's missing. Then the idle will hunt (though not missing) - still, no check engine light. AND these symptoms are not constant. They are intermittent and irregular. They do occur more often when the engine is warm, however. Actually, the only times it has "missed" is when the engine is very warm, it's sat for about 30 minutes or so, and upon restarting.

Fuel consumption is normal. It is not lower, nor has it incresed.

Now despite the fact that the check engine light isn't popping on, I still am frequently hooking up my OBD-II to troubleshoot. It is reading current and stored codes for fuel trim: bank 1 & fuel trim: bank 2.

I've tried fuel additives Techron fuel system cleaner w/premium petrol (twice). I've also replaced the MAF (mass air flow) sensor, yet it still gives me the codes. I'm thinking may be O2 sensor(s)???

Anybody - ideas? They're much appreciated!!!

[volvodefector79]

It must have taken a bit for the ECU to recognize the faults again after I cleared the codes (and replaced the lamp). Duh! The light has come on since. I don't know why I'm happy about that...

Still getting the same codes. Can anybody tell me if fuel trim bank 1 & 2 indicate the upstream 02 sensors???