P0421 code! help!
So for a while now I’ve been getting the p4021 code that says “warm up catalyst efficiency bank 1 below threshold “. I’ve read that either my car could be bad, or one of my 02 sensors is bad. My front 02 sensor keeps jumping from high to low voltage. Any one know what the voltage is supposed to be at? Thanks for any help on this I really want to get rid of that CEL.
Comments
That code is essentially the computer telling you “The catalytic converter is not operating at a necessary efficiency.” That could be cause by any number of things. Clogged Catalytic Converter, Bad forward O2 sensor, Bad rear O2 sensor, carbon buildup, clogged fuel filter, etc. Anything that affects the combustion in each cylinder.
I’ve got a similar code on my Subaru, which I’m putting down to a clogged cat as it whistles at high RPM. See what other symptoms your car is telling you, and that’ll help you narrow it down.
There’s usually YouTube videos showing diagnosis and repairs of most trouble codes. Just need to do a little digging.
If the voltage is jumping that much though, it is a sign that your likely culprit is the O2 sensor; you would just need to find a good way to confirm beyond reasonable doubt before you go replacing things to see if that helps (which can get very expansive if you don’t get it right the first time).
Between 200 & 800 mv , pump propane into your air intake and your short term fuel trim should rise. If it doesn’t your o2s1 is bad