I have a 2000 C2 with a CEL code of P0153 "Generic O2 sensor, CKT Slow Response, Bank 2; Sensor1" which is the pre-cat O2 sensor on the passenger side bank. I very recently had that cat replaced. Within 15 miles of that, and seeing the aforementioned CEL for the first time, I replaced the affected O2 sensor and drove for 60 miles with no CEL. Upon the next time out, the CEL reappeared after 5 miles. I read the same exact code, recleared it again, but within 10 additional miles it came on again. I contacted the dealer, and the Porsche bulletin he had said "check for exhaust system leaks" and if none, replace O2 sensor. There are no leaks, and the sensor is brand new. Anybody out there have any ideas? I have noticed at idle a very slight roughness about every 5 to 10 seconds that lasts a couple of seconds and then settles down. Mind you, it is very slight roughness not visible on the tach. Please help, my dealer seems to be at a loss as to the cause.

 

Oh, you are gonna love this one!! Upon calling the dealership (a well respected Bay area center) once again, and speaking with the actual tech who worked on the car, I asked him if it was possible that the 2 sensors (pre and post cat) could have been mixed up and incorrectly installed? I could hear the wheels turning, then I heard in the background "well, we have done that before". Oh God!! $180 per hour and they put the sensors in backwards; in other words the post cat sensor in the pre cat position, and vise versa. Can you believe this! I buy a $104 sensor and spend hours messing with this, and finally reversing the sensor positions, because the $180 per hour dealership can't keep 2 sensors straight. Can you say felt pen? Amazing. What is this world coming to? I have driven it about 60 miles at this point, and so far no CEL. It passed its smog check with flying colors. Isn't it incredible how well they work when you CORRECTLY install the sensors? Who would have ever thought?