HO2S Insufficient Switching Bank 1 Sensor 1
2002-2009 GMC Envoy 4.2L I6
Description
The PCM monitors how frequently the upstream O2 sensor on Bank 1 switches between rich (above 600mV) and lean (below 300mV) readings during a specified timeframe. A lean-to-rich switch occurs when voltage changes from less than 300mV to more than 600mV. P1133 sets when the PCM determines the sensor did not switch enough times.
Symptoms
- Check Engine Light
- Poor fuel economy
- Rough idle
- Engine misfires
- Hesitation during acceleration
- Failed emissions test
Common Causes
- Faulty or lazy upstream O2 sensor
- Exhaust leak near sensor
- Vacuum leak
- Fuel delivery problem (weak pump, clogged injector)
- MAF sensor contamination
Diagnostic Steps
- Monitor O2 sensor switching rate with scan tool
- Check for exhaust leaks near sensor
- Perform smoke test for vacuum leaks
- Test fuel pressure and injector operation
- Clean or test MAF sensor
Repair Notes
Most commonly caused by a failing O2 sensor. Replace upstream O2 sensor Bank 1. Check for exhaust leaks that could dilute exhaust readings.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
P1133 on Other Vehicles
Common Questions
What does code P1133 mean on a 2002-2009 GMC Envoy?
P1133 stands for "HO2S Insufficient Switching Bank 1 Sensor 1". The PCM monitors how frequently the upstream O2 sensor on Bank 1 switches between rich (above 600mV) and lean (below 300mV) readings during a specified timeframe. A lean-to-rich switch occurs when voltage changes from less than 300mV to more than 600mV. P1133 sets when the PCM determines the sensor did not switch enough times.
What are the symptoms of P1133 on a GMC Envoy?
Common symptoms of P1133 include: Check Engine Light, Poor fuel economy, Rough idle, Engine misfires, Hesitation during acceleration, Failed emissions test.
What causes P1133 on a 2002-2009 GMC Envoy?
Common causes of P1133 include: Faulty or lazy upstream O2 sensor, Exhaust leak near sensor, Vacuum leak, Fuel delivery problem (weak pump, clogged injector), MAF sensor contamination.