My GT3 stalled and when I restarted it the check engine light came on after about half a mile. OP and temp were fine. I changed the cats to 100 cell race cats and I also put on headers from FVD. I left the stock mufflers on. I drove the car this way for about 150 miles until the light came on. Are these mods enough to screw up the computer? All of the O2 sensors were hooked up.

 

I would check the post cat O2 sensor and the pre-cat lamda sensor to make shure they didn't vibrate loose or something. Also make sure that the are installed in the right order. The blue wired sensors are pre-cat and the black wired sensors are the post cat O2 sensors...

 

Headers & Race Cats, wasn't your GT3 fast enough?

 

As a past race driver I can say honestly say that "one can never have enough horsepower".


I will also takes this opportunity to respond to Rocketman. The O2 sensors are in the correct position and they appear to be intact at both ends. I will drive the car for another 100 miles and see if the computer resets itself.

 

Karl, hmmm

The only other thing I can think of are as follows, if the problem relates to the exhaust system:

1) I have 100 cell cats(Europipe) and have had no problems with about 1000 miles on them so far. Europipe did match the chemical formula coating on the cats itself to match Porsche spec and has guaranteed that they are OBD2 compliant. I am not sure if it's the chemical coating on the cats that makes them OBD2 compliant or not. My thought is yes, it's the coating that filters(changes the chemical makeup of the exhaust emissions) out the bad emissions and when the sensors analyze the exhaust they send the paramters back to the computer and check to see if they are within OBD2 specs...If they are out of spec, a Check Engine Light (CEL) is thrown.

2) Fried O2 sensor, but it seems unlikey with so few miles on the cats.

3) It's possible the changed headers make it so that the sensor readings do not conform to the set parameter guidelines in the computer. I think that is also unlikely...

I think the cats that are the more likely suspect...

Best of luck with tracking down the problem and please inform us what it is once it's diagnosed. Thanks

Chris