girlfriends car,2001 malibu 3100 v6

motor revs up smooth without hesitation

convertor was professionally replaced not long ago

before exhaust work was done i did all the head gaskets and intake gaskets torqued to spec ( intakes were best ones available)

car runs below half mark and loses absolutly no coolant

There was also a random misfire code not sure if its still there but ill check.

all spark plug wires and plugs are newer.

So is bank one the rear oxygen sensior right behind the rear head?

please help i have done alot of work to this car and i hate to see the check engine light on, also car surges a little bit on the freeway ,car has 167k, thanks

 

okay i had the same problem heres what i did first take that o2 sensor out and lay it on something still plugged in and then start the car clear all codes first if the problem goes away then its a clogged cat but if the problem is still there like mine was then its the o2 sensor good luck

 

99% of the time the code is a bad cat. We stopped using aftermarket cats because more than half fail in less then a year. Only the top notch aftermarket ones work. We use dealer cats on almost everything OBDII and never had a problem since.

 

But doesnt bank1 usually refer to a specific bank/side (cylinder 1 side in this case?) of engine indicating 02 sensor? Ive fixed alot of cars but honestly i havent had alot of 02 sensor issues

 

Bank 1 is the side where cylinder #1 is. Bank 1 sensor 1 is the first o2 on that side. Bank 2 sensor 1 would be the first sensor on the other side. Bank 1 sensor 2 would be the second one on cylinder 1 side. Sensor 2 is always behind the cat. On your car you only have 1 cat so you have B1S1, B1S2, and B2S1. On a vehicle that has a cat on each side of the engine would have B1S1, B1S2,B2S1, B2S2. Bank 2 sensor 2 would be behind the cat on cylinder #2 side.If it was a ford then it would be on cylinder #5 side. Chevy and most other makes would be on one side 1, 3, 5, 7 other side would be 2, 4, 6, 8 but ford goes 1, 2, 3, 4 and the other side 5, 6, 7, 8 . You can put O2 sensors on it but it will not fix it. You only have one cat refered to as Bank 1. If you had 2 cats it could set a code PO421 indicating converter effiency on bank 2.

 

ok that makes more sense now, thank you so much, yea im guessing oxy sensor code would be different and specify which sensor. the convertor was not put on by the dealership and im sure it was not factory. especially not for the 100 or 150 bucks she paid to have the tailpipe/convertor/and muffler put on, she thought she was getting a deal cuz her dad knew the mechanic. guess you get what you pay for.