P0133
PowertrainOxygen Sensormoderate severityO2 Sensor Circuit Slow Response Bank 1 Sensor 1
What P0133 Means
The upstream O2 sensor on Bank 1 is responding too slowly to fuel mixture changes.
Symptoms
- Check Engine Light
- Poor fuel economy
- Failed emissions test
- Slight hesitation
Common Causes
- Aging O2 sensor
- Contaminated sensor (oil/coolant/fuel additives)
- Exhaust leak
- Wiring issue
Diagnostic Steps
- Monitor O2 sensor switching frequency (should be >6 switches in 10 sec)
- Check for exhaust leaks
- Inspect sensor for contamination
- Test response to induced rich/lean
Where to start: Replace O2 sensor. This is a common wear item.
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