01 QX4 "Service engine soon" light on

[computerdna]

Hi everyone,

The "Service Engine Soon" light came on one week ago. The code and description from scan is: P0420 - Catalyst efficiency low bank #1.

My guess is the O2 Sensor, but which one? I think the truck has 4 O2 sensors, which one is bank #1?

Can I clean the O2 sensors? if yes, how?

Any suggestions?

Thanks.

[NISTECH]

I believe there is a tsb on this incedent which requires a ecm reprogram. this is a repair only a dealer can perform. but be aware we have had to replace a couple cats on the pathfinder because they were truly no good. I will see if I can get you a tsb on the reprogram today and post it tonight. the O2's are not effected by this it is a tolerance error in the ecm that has caused the light. the reprogram will open up the tolerance for failure points in the self diagnostic program in the ecm.