SES light just wont stop...

[backinblackgtp]

since i bought my gtp in november i have replaced the high flow cat twice and now have a 3in DP, the SES light code p0420 has come up 4 times, which is "cat efficency behind threshold.... since this keeps happening, and i already replaced the rear 02 sesnor, should i just get a rear 02 sim, or is this a different problem?

thanks

[TheOtherNick]

If you would have read high flow cats will still set the code sometimes. Find someone with a tuner and have them tune out the code.

[98GTPCALGARY]

do you still have the stock pcm? If you do, I would suggest getting an aftermarket one (best thing I have done to my GTP) and you can have it tuned to delete that code.
Or if you have an aftermarket one already get it tuned for that like '01GTP' said.

[2000GTP]

i just ordered a pcm a week ago, havent even had it in my car for a week..... just my luck, so i guess o2 sim is the best thing to do now?

[98GTPCALGARY]

that will work, if you cant get somebody to re-tune your pcm

[2000GTP]

i just ordered a pcm a week ago, havent even had it in my car for a week..... just my luck, so i guess o2 sim is the best thing to do now?

By the way that wasnt me. lol backinblackgtp was at my house and i was still logged in haha. i fortunately have the code deleted from my pcm