Just recently purchased the 2000 Trans Am in my sig and was running fine. I was sitting at a light yesterday when the engine suddenly stumbled and dropped below 500rpm at idle. It quickly went back up and then the SES light came on.

I got it scanned today and this is what came up:

P0171 Fuel bank 1 too lean
P0174 Fuel bank 2 too lean
P0300 Cylinder misfire detected
P0405 voltage signal from EGR Sensor "A" too low

Here is the kicker, the car still runs strong at WoT and normal acceleration but occasionally today at idle it will sink below 500rpm only to go back up to normal quickly.

I have searched here on the forums for all the codes but couldn't find any related searches having to do with all 4 of these codes at once, just the lean codes.

I am thinking the Lean condition is causing the misfire code, but I am concerned about all 4 codes showing up at once suddenly.

So far I have cleaned the MAF with electrical component cleaner but the SES light stayed on although the car ran fine after that.

Any suggestions?

 

If you changed things but didnt reset the PCM the code is stored until cleared. You can have someplace like Autozone clear it or just go out lift the hood and pull the PCM fuse and the one on dash fuse panel for about 10 minutes and you'll be good to go. Try that and see if the codes come back.

 

Yeah I didn't try that. I just assumed that it was after 3 ignition cycles where the problem didn't happen again it would reset itself.

 

To reset the comp.
turn on key without starting the motor
pull PCM IGN & PCM BATT. fuses in the underhood fuse panel
wait 10 minutes
turn off key
reinstall fuses and start.

 

Reseting the PCM didn't help. Still codes, all 4 still. I guess the next step is checking the EGR? Would a faulty EGR system throw all 4 codes though? My idle RPM is still normal but I am noticing that if i rev the engine in Park the RPM goes up normally but goes down abnormally slow. I can't really notice any stumbling or hesitation when accelerating and it still runs and pulls strong as hell so it's not making sense to me.

 

when mine was throwing codes ( due to dirty MAF) I cleaned the MAF and the SES light was still on. I drove it for around 20-30 miles and the codes went away- they reset themselves.

 

leaning out... could be the EGR is causing the car to run lean?

I'm getting rid of my EGR whenever I can get around to it.

 

UPDATE: Well, I found a hairline crack in a vacuum hose and fixed that, reset the PCM again, and the SES is gone.

However, RMP idle speed is still a bit low, like around 500rpm. Not sure what that's about, maybe IAC?

 

It will relearn proper idle as you drive it.