P0133
Medium SeverityO2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
Emissions System
What Does P0133 Mean?
The upstream O2 sensor on bank 1 is responding too slowly to changes in exhaust oxygen content. Known as a lazy O2 sensor.
Common Fix
Replace O2 sensor
Estimated Cost (DIY)
$30 - $100
Symptoms
- ⚠️Slightly poor fuel economy
- ⚠️Failed emissions test
- ⚠️Occasional hesitation
- ⚠️Check engine light
Common Causes
Aging O2 sensor with worn elementlikely
Contaminated sensor (from oil burning or coolant leak)possible
Exhaust leak diluting readingpossible
How to Diagnose P0133
- 1Monitor O2 sensor switching rate (should be 1-3 times/second at 2500 RPM)
- 2Check for oil consumption or coolant leak
- 3Inspect for exhaust leaks
- 4Replace if response time exceeds 300ms
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Frequently Asked Questions
- How long do O2 sensors last?
- Most O2 sensors last 60,000-100,000 miles. After that, they get lazy and respond slowly, triggering P0133.
- Is P0133 a big deal?
- Not an emergency, but fuel economy suffers and you will fail emissions. Replace the sensor when convenient.