Strange Issue???

[rushr]

So I just bought my Yukon a few days ago. It had a CEL, but the previous owner assumed it was something to do with the supercharger. I ran the codes and had about 9 different ones show up (I should have wrote them down but I didn't). I cleared the codes and drove for about 20 minutes and the CEL never came back. I read them again out of curiosity and when I hooked up the code reader the CEL came back on and had 3 codes (P0140, P0171, P0300). When I started the truck the light went away. I drove for about 10 minutes and checked them again and came up with 3 codes (P0135,P0140,P0171), the misfire code went away. This morning I get up and start the truck and there are no CEL's, I get to work and hook up the scanner and the light came back on with 2 codes (P0135,P0140). I start the truck back up and the CEL goes away...

I guess what I find strange is that when I hook up the scanner the codes come back, but when I start it they go away. The initial scan was the only one out of all of them that I actually cleared the CEL with the scanner.

 

[rushr]

Anything? I've checked it off and on some more and now it's down to only the P0140 (O2 Sensor). This time it actually came on while driving...but for the most part once I would start the truck the CEL would go out and stay out.

 

[blackcoffee]

Sounds like the PCM needs tuning? Problems with tranny at all? Check your o2 sensors, wires, distributer cap n rotor, catalytic converter, truck 4wd?

 

[rushr]

I haven't noticed anything with the tranny, everything seems smooth. I'm going to be looking at those other things this weekend. I plan on changing the plugs and wires and will be looking at the distributor. I haven't checked into the O2 sensors yet, but I half expect a code with those considering I have headers. At least previous vehicles I've owned were usually prone to that. Yes, the truck is 4WD.