P1133 GMC Possible Causes
What does this mean?
- Faulty Heated Oxygen Sensor (HO2S), Bank 1 Sensor 1
- Vacuum leak
- Faulty Heated Oxygen Sensor (HO2S), Bank 1 Sensor 1 harness is open or shorted
- Faulty Heated Oxygen Sensor (HO2S), Bank 1 Sensor 1 circuit, poor electrical connection
How to Fix Code P1133 GMC?
Start by checking the “Possible Causes” listed above. Visually inspect the corresponding wiring harness and connectors. Look for damaged components and check for broken, bent, pushed out, or corroded connector pins.
When is the code detected?
If the Powertrain Control Module (PCM) determines that the front HO2S has not switched enough times, the PCM will set code P1133.
Possible Symptoms
- Engine light on (or service engine soon warning light)
P1133 GMC Meaning
The Powertrain Control Module (PCM) monitors the Heated Oxygen Sensor (HO2S) activity for 90 seconds after closed loop operation begins. The PCM determines if the front HO2S is working properly by counting the number of HO2S-1 Lean/Rich (L/R) and Rich/Lean (R/L) switches.