Originally Posted by knuckles27
Went to AutoZone last night. I left the ticket in my car but I am pretty sure the code was P0240 for the cat. This is right in line with the Subie dealer thing the SPT exhaust was causing a false positive. They are installing an Access Port and tuning the car on Monday.
IA you continued to mention the cat code P0420 but the OP posted P0240 which if I remember is a wastegate code for over boosting. This sounds like an issue of either a poor tune, no tune for an aftermarket downpipe, or possibly a failing bcs. Either way I just wanted to point out the little confusion on which code was referenced.