P0133 — O2 Sensor Circuit Slow Response (Bank 1, Sensor 1)
Drive with caution — fix soon.
What P0133 means
P0133 means the front oxygen sensor on Bank 1 is switching between rich and lean too slowly for the computer's liking. A healthy sensor reacts quickly; a slow one is usually aged, contaminated, or coated with deposits. Replacing it restores accurate fuel control and helps your catalytic converter and fuel economy.
Common symptoms
- Check engine light on
- Noticeably worse fuel economy
- Slightly rough idle or mild hesitation
- Failed emissions test
- Engine generally drives normally
Common causes
- Aged or worn-out upstream oxygen sensor
- Oxygen sensor contaminated by oil, coolant, or silicone
- Carbon or soot buildup slowing the sensor
- Minor exhaust leak near the sensor
- Deteriorated sensor wiring or connector
- Fuel quality issues affecting sensor response
Typical repair cost
$150 – $450
Varies by vehicle and root cause.
Frequently asked questions
Can I drive with a P0133 code?
Yes, it's generally safe to drive short-term, though you may use more fuel. Since the sensor is wearing out, plan to replace it before it fails completely.
How much does it cost to fix P0133?
Replacing the upstream oxygen sensor usually costs $150-$450 including labor, depending on your vehicle and the part used.
Is P0133 serious?
It's moderate. Your car remains drivable, but a slow sensor hurts fuel economy and emissions and tends to get worse over time.
Why is my sensor slow instead of just failing outright?
Oxygen sensors age gradually. Contamination and deposits slow their reaction long before they stop working, which is exactly what P0133 detects.