My cel came on and the code is p0420 which is the cat on bank one, my question is what side bank 1 is on, the driver or passanger side, i was hoping it would be a bad 02 but the 02s would throw a different code right?

 

What year, engine and milage do you have?

 

A code P0420 may mean that one or more of the following has happened:

Leaded fuel was used where unleaded was called for
An oxygen sensor is not reading (functioning) properly
The engine coolant temperature sensor is not working properly
Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
Retarded spark timing
The oxygen sensors in front and behind the converter are reporting too similar of readings

 

its an 04 5.4 90k..i thought the 02 sensors had there own code?

 

They do have there own codes, it doesn't always mean that the sensor it bad. The code can be caused by numerous conditions, like a vacuum leak. Did the light just come on? Has the truck been running rough? Did you run over anything that could have damaged the wiring to the sensor? Fill out your information and state, join a local chapter.

 

The light came on a few days ago, but the truck is running good,2 weeks ago i cleaned the throttle body with some throttle body cleaner, but i cant see that messing anything up.