wroehr

Just drove the car a little hard on highway and boom... P0431 and P0421 (Catalyst 1 efficiency below threshold bank 1 and 2)
No difference in drive-ability. I am at 1/4 tank of fuel and always use shell premium.

Previous owner installed intake manifolds and o2 sensors 1,500 miles ago. Should I just clear and see what happens? I run techron every other tank of gas.

ATX_Native

I get a CEL pop up for P0004 every 12-18 mos.

I reset and live my life for another year.

Carreralicious

Might want to take it easy on the Techron. It states to use it like once every 2 or 3K miles, not every other tankful cause premium gas already contains some injector cleaner in it (in smaller doses). I put in Driven Injector Defender a few times in a row and ended up with a CEL for a clogged fuel purge valve that had to be replaced due to all the crap that got unlodged by the cleaner.

wroehr

Good to know! Luckily, I've missed the last 2 tanks with Techron so its just been shell.

wroehr

I cleared codes and drove 30 miles with 6 key cycles. Not back on yet! I was hoping for bad cats to inspire me to get new headers.