Originally Posted by 10EvoX

About a week or 2 ago my SES light came on with the P0420 code (Catalyst System Efficiency Below Threshold (Bank 1)). This was a day after I had taken my car in to get TPMS sensors programmed and they also flashed the ECU for an AWC recall.

Anyways, after using Cataclean and resetting the code, it still has not helped, and I've lost several MPGs. Yesterday, there was a faint "rotten egg" smell after I drove home, which apparently is indicative of the cat taking its last breaths.

My question is why did it happen? I've got the Perrin downpipe with high flow cat, and its barely 2 years old. The cat shouldn't die this soon. Haven't done any performance mods since getting tuned at Ivey. Spark plugs were changed around 15k or so (car at 34k miles now). I fear that just replacing the cat will be a band-aid fix, and may not address the root cause of the problem.

Any suggestions? Also, I will have to replace the downpipe/cat. Any suggestions as to what I should get?

Any help would be greatly appreciated,

thanks

Originally Posted by ikt

why are you running a catted downpipe at all? Check your state laws, maybe you can just weld in a hiflow cat ($50) in your catback and run a catless downpipe. Cat converters are nothing but problems.

Also, ProTip: stock cat is hi flow.

regardless, you will likely NEVER get a CEL for cat after a tune. There's no way to get it, the computer just doesn't read it, dead or not, doesn't matter if it's shut off.