OBD-II code guide
P0133 Oxygen Sensor Circuit Slow Response Bank 1 Sensor 1
P0133 means the upstream oxygen sensor on bank 1 is responding slower than expected.
What it means
Fuel control may be less accurate because the sensor signal is delayed.
Common symptoms
- Check engine light
- Poor fuel economy
- Failed emissions test
- Usually mild drivability change
- Possible hesitation
Likely causes
- Aging oxygen sensor
- Exhaust leak
- Contaminated sensor
- Wiring resistance
- Fuel mixture problem
First checks
- Inspect for exhaust leaks.
- Review live sensor response.
- Check for oil or coolant contamination clues.
- Confirm sensor location before replacement.