Why is there a P0420 code on my Chevy S10?
Why is there a P0420 code on my Chevy S10? The P0420 code in a Chevy S10 will often be thrown one of your oxygen sensors are not functioning properly. Typically, the code will be triggered by the upstream oxygen sensor (before the converter). What does code P0420 mean on PCM? Code P0420 represents a problem. However, if the downstream O2 sensor starts sweeping between rich and lean, or constantly reads a rich or lean condition, that’s an indication to the PCM that the cat converter isn’t doing its job of cleaning up the PCM’s mistakes. What is the shifting...