P0133
Medium SeverityO2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
Emissions System
P0133 — Instant Answer
O2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
Severity: MEDIUM SEVERITY
Meaning: The upstream O2 sensor on bank 1 is responding too slowly to changes in exhaust oxygen content. Known as a lazy O2 sensor.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $30 - $100
Most common causes:
- 1. Aging O2 sensor with worn element (35-45% of cases)
- 2. Contaminated sensor (from oil burning or coolant leak) (10-25% of cases)
- 3. Exhaust leak diluting reading (10-25% of cases)
Symptoms
- ⚠️Slightly poor fuel economy
- ⚠️Failed emissions test
- ⚠️Occasional hesitation
- ⚠️Check engine light
Related Symptoms
Common Causes
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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Related Symptoms
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Related Codes
General fault with the upstream O2 sensor on bank 1. This sensor monitors exhaust oxygen to control fuel mixture.
The upstream O2 sensor on bank 1 shows no switching activity. The sensor may be dead or disconnected.
The heater in the upstream O2 sensor on bank 1 is not working properly. The heater brings the sensor to operating temperature quickly.
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.
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Author & Review
Written by AllOEMManuals Editorial Team. Reviewed by ASE-certified technicians and updated with factory-reference checks for fitment-sensitive steps.
This guide was drafted with AI assistance and reviewed for accuracy by a human editor.
Last updated: 2026-05-07