Originally Posted by IA Performance
NoGraffix - No mistake on my end nor your end. JML281's code reference is a bit vague. There is reference to the Cat as well as p0240. P0420 is for Catalyst Efficiency, which seemed to make the most sense given the details in post 1 and 9. A p0240 code would most likely of experienced fuel cut from over boosting. Fuel cut is quite dramatic, and usually freaks people out, yet no mention of it. I ran with the p0420 idea since p0240 symptoms were not mentioned. I could be wrong, but I do know the difference of the 2 codes.
The big question is: what does the little piece of paper on JML281's dash say
You are correct, until the OP can verify the actual code no one will be able to help. Fuel cut due to overboosting is quite dramatic and pretty unmistakable. There is more then enough info here to help the OP be the code 240 or 420