i have a 2001 gmc 1500 5.3 it is giving codes P0135 and P0420

Question

I have replaced the bank 1 sensor one a few times and the problem isn't going a way I have also check all wiring to the sensor and all looks good. any ideas?

Answer 1

P0135 -02 sensor heater circuit malfunction Bank 1 Sensor 1

The heater sensor for the 02 is only turned on during cold start , The PCM monitor its voltage if it goes below its threshold then you get P0135, You are going to have measure for voltage at its heater circuit, P0420 can be the result of a failed 02 sensor.which is catalytic convertor on Bank 1This year make and model is also known for its failing ground problem that tends to code a ABS and 02 code condition the ground is near the ABS module