2005 GMC Canyon SLE P1133 and P0136 O2 Sensor Codes - Rough Idle at Warmup, 550 RPM

Model: 2005 GMC Canyon SLE Fault Code: P0136 Posted: 2017-11-13 12:38

Hi everyone. My 2005 GMC Canyon SLE has started idling roughly once it reaches operating temperature, with the engine running around 550 RPM. The check engine light has been on for several weeks due to a stuck-open thermostat. After checking the codes again, I'm now seeing two oxygen sensor fault codes: P1133 and P0136, along with an IAC valve rpm low code (P0506). Two months ago, I replaced the upstream O2 sensor as it was failing, but both sensors showing faults simultaneously is puzzling. The wiring appears to be in good condition. I'm planning to clean the throttle body next and monitor whether the codes return or resolve on their own.