P0420 GMC -

Question

help me with o2 sensor codes

Answer 1

Hi there,

This is not an O2 sensor code. This is a code for the bank 1 catalytic converter below threshold. This usually indicates there is a problem with the converter and it must be replaced to resolve the issue. If the problem is being caused by the rear O2 sensor, then you need a scan tool that can read the live data to confirm it. Normally you will not get a code for the converter when the sensor is the problem.