P0420 code at 171,000

[gero808]

Im running the P0420 code and my car has 171,000 miles, am I going to have to replace the cat along with the Oxygen sensors?

[ScoobySnack]

Well, it could be a very expensive fix to replace the cats and the 2 o2 sensor. I had this happened last year and replace first my rear o2 sensor first and that did not work and then went ahead and replace the front one as well and it solved my problem. Seeing that your mileage on the car is quite high it is a safe bet that either one of the o2 needs to be replaced always. They are not cheap fix but in the end will benefit you in gas mileage as well. So worst case replace your cat, try to eliminate the problem one item at a time. Good luck!

[LiCelsior]

it'll also help to save u some gas mileage.

[gero808]

well right now Ive been clearing the code everytime it comes up but that gets annoying after awhile.

[Huffer]

Replace your sensors and start saving up for new converters.

[ScoobySnack]

Well said. O2 first than the expensive pieces of metal!

[ShadowGT]

Im running the P0420 code and my car has 171,000 miles, am I going to have to replace the cat along with the Oxygen sensors?

Do you have aftermarket headers on your car?

[gero808]

nope completely stock.

[ShadowGT]

nope completely stock.

Just figured I'd ask. Sometimes when you run aftermarket headers with the increased exhaust flow across the downstream O2 sensor, you get that p0420 code.

[ouch1011]

Personally I'd suggest taking the car to a reputable shop and having them diagnose the problem properly. The reason is because it could be caused by either or both of the O2 sensors, it could be caused by any other engine sensor that may cause the engine to run a little worse and increase engine emissions, or it could be caused by the cat convertors. A proper diagnosis will tell you what the problem is rather than guessing and "shotgunning" parts until you guess correctly.

[stu-nami]

How difficult was it for you to replace the O2 sensors by yourself???....cuz it looks like my cat is below the threshold and I had the same codes come up today I'm at 168000 miles going to be over 170k after I drive to colorado tomorrow from idaho

[anothernord]

O2 sensor are a pain unless you spray tons of PB blaster on them and let it soak for hours. Especially on high-mileage cars.

My advice would be to find a set of used cats and bolt em on. Getting brand new ones would be a waste.

[LiCelsior]

i used a torch on them first before i put the o2 socket to turn it. worked good then apply anti seize when reinstalling.

[subyfreak619]

crows foot.... + pb blaster :smt025

[stu-nami]

Ya maybe when I'm near denver I can find some used cats off one cuz they're all over the place so I'm sure a junk yard would have them

[jey]

If you have a good OBD-II reader you can do your own diagnosis by looking at the voltage readings from your O2 sensors.

[gero808]

whats the voltage readings that shows that its still good?

[jey]

It should be cycling somewhere between .2V and .8V. If it's pegged at 0V or something way high then the O2 sensor is bad.