P1133moderate severityPowertrain
HO2S Insufficient Switching Bank 1 Sensor 1
on 1997 Buick Century 3.1L V6 · FWD
What this code means
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.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1