sbuswell

I had my RT Cat installed about 800 miles ago and now as of Friday my car is throwing a P0420 DTC. I figured if it had something to do with the Cat it would have happened sooner, but whatever. Anyway I seafoamed my car, cleared the code and took a drive. The next day I changed my plugs (NGK Iridiums of course). I took a drive and noticed my car felt much smoother and responsive than before. I drove around all weekend and the code didn't come back. Today the CEL came on again, I came home and sure enough, same code. I am hesitant to think it is my EGR valve as I routinely use fuel system cleaner(BG 44K or Gumout Regane) in the gas tank and use seafoam through the induction system. Any other ideas on what it could be? Would my regular maintainence not help clean the EGR port?

fsttyms1

It may be the rear 02 causing the code.

sbuswell

I changed the rear 02 2 weeks ago when I had a CEL for a heat circuit.

Excelerate

iTrader: (1)

The secondary 02 sensor is there to see if the cat is doing its job. The RT cat flows much more than the factory cat. The ECU has very strict parameters as what is acceptable on exhaust flow so it's possible it's throwing a code because it is seeing more flow than it wants, not b/c the cat is bad or defective but b/c it is flowing more than the OE cat. However, I have sold a number of the cats to TL/CL guys and most customers don't throw a CEL so I would check to make sure everything else is functioning properly.

Rajca

iTrader: (8)

u could always put a cap on the o2 sensor to decrease what the o2 sensor reads.

fsttyms1

sbuswell

sounds like a plan. Are you referring to the no-foul spacer or something else?