GRK

Hi All,

I had the stupid code p0420. So I seafoamed, cleaned the EGR port both per the DYI's and changed the EGR and bank 1 O2 sensor in that order over the last 2 weeks. The 02 had some serious carbon on it so I changed it 3 days ago (about 45 miles). The check engine light came on again today with the same code. Should I change the second 02 sensor? Any suggestions?

Thanks

fsttyms1

420 is usually the rear 02 or the cat. What 02 did you buy? one from the dealer or one from a parts store?

GRK

I bought a bosch from the autoparts store. Is there a way to test the cat?

fsttyms1

Bosch. Many have had issues with those in the past. But like i said before, that code is usually the rear O2 or the cat. There isnt a way you can test the cat, but muffler shops usually can.

TLer trash

Try running a can of bg44k in a quarter tank of gas. Do some wide open throttle accelerations and a highway cruise around 2000 rpm for 15 - 20 minutes. {use d4 if nec} You might have to repeat this process, but if two times don't do it, I don't think more will help.
As fasttyms said, convertors and o2 sensors are typical culprits. If you have to have it diagnosed, make it clear you expect a guarantee if the light comes back on. The reason I say this is that aftermarket catalytic convertors are not 100% on this. If you can get one that is certified for sale in california, you get a better guarantee, and a better probability of keeping the light out. Probably the cheapest "fix" that's close to 100% is to use a spark plug non-fouler on the rear o2 sensor.[pretty sure it's illegal, but you'd smog just fine if no visual inspection]

GRK

OK. So I had the check engine reset. I drove for about 100 miles and the car passed inspection. The only thing I did was run a full tank of shell v-power.

Thanks for all your help

ArTL-S

just to let you know i used a bosch o2 sensor and it was crap so i choked the money and bought one from the dealer. it hurts a little but its alot better

AlanW

Bosch usually, at least use to, makes good stuff, but something about their O2 sensors. I use to have a Dodge Daytona and those cars also had problems with Bosch O2 sensors.

RACINGHART03

iTrader: (2)

Yes. Your code P0420 is specific to your catalytic converter efficiency dropping below threshold. Why would you look anywhere else? I fix these regularly by.....replacing the catalytic converter.