P0133: O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
System: Catalytic converter and oxygen sensorsThe front oxygen sensor on bank 1 is reacting too slowly to changes in the exhaust.
Severity: 1 of 4
Generally safe to drive. You may see slightly worse fuel economy, and the car may fail an emissions test. Fix it when convenient. If the engine runs rough or the light flashes, treat it as a more serious problem.
Estimate range covers the repairs listed below; see the cost breakdown. A flashing check engine light, a hot temperature gauge, or brakes that feel different mean stop driving and get help.
What P0133 means
A healthy front oxygen sensor switches quickly between rich and lean readings as the computer adjusts fuel. The computer times those switches. P0133 sets when the bank 1 front sensor responds more slowly than it should once the engine is warm.
Oxygen sensors age. Over many miles the sensing element gets coated and slows down, which is why P0133 often shows up on high mileage original sensors. Coolant or oil burning in the engine, or silicone from the wrong sealant, can speed that up.
Exhaust leaks near the sensor and intake air leaks can also upset the reading, so check those before replacing the sensor.
Common causes (cheapest likely first)
- Aging or contaminated front oxygen sensor. The most common cause.
- Exhaust leak near the sensor. Outside air dilutes the signal.
- Damaged wiring or connector. Heat from the exhaust can melt insulation.
- Intake air leak or MAF problem. Unusual mixture swings can confuse the test.
Symptoms
- Check engine light
- Slightly worse fuel economy
- Often no noticeable change
- Possible failed emissions test
DIY difficulty: Easy to moderate
Front sensors are often reachable from above. A seized sensor may need penetrating oil and an oxygen sensor socket. Use anti seize only if the new sensor does not come pre coated.
Tools: OBD-II scanner with oxygen sensor data, Oxygen sensor socket, Penetrating oil, Multimeter
Estimated repair cost
This is an estimate, built from typical parts price ranges plus labor hours times an assumed shop rate of $110 to $190 per hour. Actual prices vary by vehicle, region, and shop. Diagnosis fees are often extra.
| Repair | Parts | Labor | Estimate (low / high) |
|---|---|---|---|
| Front oxygen sensor | $40 to $200 | 0.3 to 1.0 h | $40 + 0.3 × $110 = $73 $200 + 1.0 × $190 = $390 |
| Exhaust leak repair | $15 to $150 | 0.5 to 1.5 h | $15 + 0.5 × $110 = $70 $150 + 1.5 × $190 = $435 |
| Wiring repair | $5 to $40 | 0.5 to 1.5 h | $5 + 0.5 × $110 = $60 $40 + 1.5 × $190 = $325 |
Watch a repair video
Search YouTube for “P0133 fix” videos. Pick a recent video that matches your engine, and confirm the diagnosis before buying parts.
By make
This code works the same way on every make. See brand notes.
Repair manuals
Step-by-step service manuals with torque specs and wiring diagrams:
Haynes manuals Chilton manuals
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Related codes
Check for recalls
Before paying for a repair, enter your VIN in the NHTSA recall lookup. Emissions parts may also be covered by a federal emissions warranty; check your warranty booklet.
FAQ
Is P0133 the same as P0135?
No. P0135 is the sensor's heater circuit. P0133 is the sensor's signal being slow. Both point at the same sensor position, and both are often fixed with a new sensor.
Can I clean an oxygen sensor?
Cleaning rarely restores a slow sensor. Replacement is the reliable fix.
Will P0133 clear on its own?
It may go away for a while, but a slow sensor usually sets it again.