P0133
O2 Sensor Slow Response (Bank 1 Sensor 1)
low
i Description
The upstream O2 sensor on Bank 1 is switching between rich and lean too slowly. A healthy O2 sensor should cycle multiple times per second. A sluggish sensor causes poor fuel control.
? Common Causes
- Aging O2 sensor
- Contaminated sensor element
- Exhaust leak diluting exhaust gas
- Fuel quality issue
! Symptoms
- Check engine light
- Slightly increased fuel consumption
- Failed emissions test
- Minor driveability symptoms
# Diagnostic Steps
- Monitor O2 sensor switching rate with scan tool
- Compare to manufacturer spec (typically >6 crosses per 10 seconds)
- Check for exhaust leaks
- Replace sensor if slow
⚙ Typical Fix
Replace the upstream O2 sensor.
Parts Needed
O2 sensor (upstream, Bank 1)
Estimated Cost
$100-$300
↔ Related Codes
Q Frequently Asked Questions
Yes, this is a low-severity code. Fuel economy and emissions are slightly affected. Replace the sensor when convenient.
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