I have a 1998 Blazer and had two codes in the PCM a P0135 abd P0146. I was searching the forum and read how common the 146 code was so I was gonna deal with that code later. The other code was B1S1 Heater performance so I replaced the sensor with a AC delco sensor. Cleared the codes and drove to work and back and both codes returned. The post cat 02 wouldnt mess with the b1s1 02 would it? I dont know why both codes returned?

 

The presence of an O2 sensor code, especially a heater code, does not automatically mean that the O2 sensor is bad. It could be a ground or other wiring problem. The P0135 Explained thread will walk you through the diagnostic procedure.

 

Thanks for the help I will troubleshoot through the charts.