Contour Enthusiasts Group Archives Forums General Troubleshooting O2 sensor mabey?

I pulled a P0420 bank one yesterday on my zetec. Reset the computer and goes away until i have to sit in traffic after work. When i come to a stop after driving the car a lot the engine sometines stumbles, doesnt stall though. Other then that everything is ok. Im thinking bad rear O2 sensor, its all rusted up and evrything. Thanks

it may be rusted up, but you said yourself that it said BANK 1 and that code IS for bank 1

the front header as you open up the hood is the bank 1 header....someone correct me if i am wrong

I do have a zetec. So i would have 2 banks? One for each O2 sensor?

Nope, you have one bank with an upstream and a downstream sensor. Upstream -> before precat, downstream -> after precat and before main cat.

oh my fault i wasnt even thinkin of a zetec, i was thinkin duratec, DUH.....


sorry

It says below threshold? Isa that downstream?

no below threshold, means like below a tolerance of the sensor......


the sensor is "sensing" that something isnt operating up to "spec"

So in other word gut the CAT to fix it?

im not sure whether thats your cat, or the sensor.....i've heard both stories

i have heard that it is the cat more though

im not really sure to give you the advice man......i dont want to give you the wrong info....maybe someone else will chime in with an answer for you

Gutting the cat will not fix it. Gutting the cat will cause a "below threshold" error code because the cat is not working effeciently.

The cat monitor is a program in the PCM on all OBD II cars that runs ocassionally to make sure that the cats are working properly. That is done with the rear O2 sensor. An O2 sensor normally is switching constantly from rich to lean. An O2 sensor mounted behind the cat switches very slowly or even almost not at all when the cat is working. When the cat has lost effeciency, the rear O2 sensor will switch nearly as rapidly as the front. When the front and rear are switching at or near the same rate, the cat monitor will recognize that the cat is "below threshold", set a code, and turn on the MIL.

Also, on a V6, bank one is the rear bank. Cylinders 1, 2, & 3 are bank one, and that is the rear bank. Cylinders 4, 5, & 6 are bank two, and that is the front bank. The numbering system goes back to rear wheel drive cars. Ford always numbered cylinder #1 as the right front. With the engine moved to the east-west position, the #1 cylinder is in the same place.