Intermittent CEL, need help.

'01 3.1L, recent LIM gasket replacement.

CEL came on, so I stopped by Autozone and had it read. Three codes came up, Low Voltage TPS, Lean Bank 1, and one other which I've forgotten. I did write them down, but because the light went off soon after I opened the hood and snugged up one of the spark plug wires at the coil I threw away the piece of paper I had them written down on.

Anyway, the light has come and gone for the past three days. It will come on completely randomly (i.e. no correlation between engine temp, rpm, load). It is off much more then it is on. Engine runs smoothly, no knocking or missing so I'm not worried about driving it.

Let me know if you have any ideas.

With so many possible reasons for the MIL to turn on, the fastest method will probably be to scan for trouble codes.

Update: Only code remaining is "System too lean". Guy at parts store thinks it's a dirty MAF.

Could be a faulty oxygen sensor.

That's a fair assessment. You could scan and monitor oxygen sensor activity to see if the signals are high enough and crossing the bias point as required (cross-counts).

Thanks for the replies, guys. Check engine light has been off for going on 3 days now. If it comes back I will head back up to scan it again. Can I monitor the oxygen sensor from the hand held scanner? Will doing this at idle be sufficient?

I just thought it was too much of a coincidence that it came on right after doing the lower intake manifold gasket, but I obviously wasn't messing with the O2 sensor.

I just thought it was too much of a coincidence that it came on right after doing the lower intake manifold gasket, but I obviously wasn't messing with the O2 sensor.

No, but any coolant or oil that went into a cylinder when it came apart can screw with them...o2 sensors hate coolant...