What does code P0133 mean?
P0133 means the control oxygen sensor before the catalytic converter on bank 1 is responding too slowly to mixture changes. This makes fine air-fuel adjustment harder, increasing fuel consumption and emissions.
OBD code P0133
The upstream oxygen sensor on bank 1 is changing its signal too slowly.
Estimated severity
Medium
Common symptoms
- Slightly unstable idle in some cases
- Small increase in fuel consumption
- Related mixture codes in some cases
Likely causes
- Aged or contaminated oxygen sensor
- Poor wiring or ground at the sensor
- Small exhaust leaks before the sensor
Recommended checks
- 1. Observe the oxygen sensor signal on a scanner, including switching frequency and amplitude.
- 2. Check for exhaust leaks before the sensor.
- 3. Inspect wiring and connectors.
- 4. If the sensor is old and responds slowly, consider replacing it.