Ok so I sold my 2005 Saab 9-2X (Same car as 2005 WRX), and the new owner got a CEL right after picking it up. The car HAD a catless downpipe on it but before selling the car I put the stock catted downpipe back in. There is still however a helix uppipe in the car.

The car has the normal 2.2k resistor installed to prevent CEL's from the missing EGT sensor on the uppipe, and as far as I know that's the only CEL an uppipe can throw, correct?

I had the new owner take the car to the dealer and they read code P0420 (catalytic inefficiency) from the car and told him he needed a new downpipe/catalytic converter. The cat has less than 5000 miles on it so I'm really doubting this is the case. Does this sound like possibly just the rear O2 sensor has gone bad?

The dealership tried to tell me that the uppipe could cause the P0420 code but I'm pretty sure that's not correct.

I'm inclined to buy an 02 sensor and install it for him. What does everyone think about this predicament?

 

the dealer is full of ****.

its possible the o2 got damaged during installation/uninstallation of the dp, but first reset the ecu, the code should go away. If it comes back, you might consider replacing it.

 

you should replace the stock uppipe, or have the new owner get engine management like a Cobb Access Port. This way the car can compensate for faster spool up and no long term damage will occur.

 

Ok so the new owner had the stock up-pipe re-installed and the dealer replaced both the downpipe/cat, and the O2 sensor. The light STILL comes on after driving for a while.

I don't see wtf else could be causing the light, any suggestions?

 

Is it possible that not having the heat shield on the downpipe could cause this? The turbo heat shield is there, but the one directly behind it which heads down along the DP is not there.