I own a 1997 Pontiac Grand Prix w/ 139K
The Check Engine Soon light keeps coming back on.

The car was just serviced - found a flake of carbon in EGR valve -
and was reset by the garage.

Also, I am thinking about buying a code reader - are the $200 models worth buying?

go here

http://users3.ev1.net/~chauvin555/LS1M

I need a more versatile tester. I also have a 1994 Ford F150 truck and my son has a Saturn.

Try this one then:

http://www.autotap.com/

Tim

Also check for broken wiring from the EGR to the PCM(ECU) and that the valve itself is working properly. I have had a problem like that once and the light kept coming back on and was a split cable.

The autotap is one of the best code readers out there.

As for your problems, I suggest scanning the car to see what the problem is.

Had it scanned today - was an internal fault code where the unit has a slightly lower than normal voltage and keeps turning on the light. Luckily is still under warranty and will be replaced tomorrow.

Great!!!. Hope is just the electrical part.

I have a heard a lot about this happening in GPs and older cars! A lot of times what happens is air gets stuck in the fuel tank and creates pressure since it's a vacum. Usually occurs when going fast around a turn or when going from one extreme speed to another like 60mph to a dead stop or a deap stop to 60mph. The newer GPs '96 and on corrected this problem.

Once right after I had just got the '98 GP back from the dealer for repairs, my Check Engine Soon light came on. I brought it back the next day and they found a vacuum hose was off and you could hear it hissing if you stood right over the engine while it was running. They reattached the hose and it's been fine ever since. But it took them awhile to find the problem. First they said they couldn't find anything wrong, but I insisted they keep on looking :-). The check engine light was never even on when I first brought it in for a bunch of stuff to be fixed. I had just spent $1600 there on repairs and was not going to settle for "we can't find it". It really sucks when a car is out of warranty.

If you guys ever have a code let us know we can decipher and get you information on how to fix it pretty quick