Maybe someone can help me diagnose this problem. My car is a '95 Z28 M6 with 73,000 miles. The SES light will pop on going down the road and then turn itself off after 15 or 20 minutes. The car seems to run fine with the light on - no obvious missing or loss of power but I'm not getting the kind of gas mileage that i used to. I think the cooling fans are coming on when the light is on. If I shut the car off and restart, the light goes out and the fans shut off. I took the car to Autozone for a scan but they couldn't read the OBDI computer. Any tips on how I can pull up the code myself and figure out what's wrong?

Thanks!

 

o2 sensor(s), unless they are new, replace them. If they are new, look towards the MAF sensor.

 

I would say O2's. had the same problem and it was an easy fix.
The typical maf code that throws when the connection breaks to the maf doesnt clear until the car is restarted if i recall.

 

I was thinking it might be the O2 sensors also - they've never been changed. What usually goes wrong with the MAF and how would you check it? I descreened it a couple of years ago - is there a recommended cleaning procedure?

 

Electical cleaning spray i hear is the best. Rubbing alcohol on a q-tip i hear works also.

 

It may or may not be the O2 sensors. You need to find someone with a scan tool or code reader that can read the '95 model.

 

Mine does that same thing and the code on the scantool say "incorrect EGR singal" or something. Probably because I don't a have a cat and it's messing up the backpressure or something I'm sure...

 

Is there any way to check for codes without a scan tool? I remember reading somewhere that you could short across a couple of contacts where the scanner plugs in and that would make the SES light flash out the error code number.

 

No, you can't flash the code by shorting the pins. I think '93 was the last year for that. It will take the correct code reader or scan tool to do it, or someone with a software program and correct cable.

 

The '95 is an odd year in that while OBDI, it has a 16 pin OBDII connector. This requires an OBDI scanner with an adaptor. As for the fans, when SES light is activated the fans come on, so don't mistake fans running for symptom of problem. Actually sounds like O2 sensor since it still runs okay, but check it out before spending money. You may be able to find a relatively inexpensive sensor checker at local parts store with which to check the sensor itself, but I would concentrate on finding someone with a scanner.

 

I will bet money its the code 32 EGR. If so a new EGR valve will fix it.

 

Thanks for the information! I'll see if I can get it scanned to pinpoint the specific error code(s).

 

Mine did that for a time, and when I pulled the motor apart I found it was the wire to the knock sensor was burnt through, so sometimes it would make connection, sometimes it wouldn't.