P0133 means O2 Sensor Circuit Slow Response (Bank 1 Sensor 1). The upstream oxygen sensor on bank 1 is switching between lean and rich too slowly, usually a sign of an aging or contaminated sensor. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0133 means
Oxygen sensors measure the oxygen left in the exhaust. Sensor 1 sits before the catalytic converter and is used for fuel control; sensor 2 sits after it and mainly monitors the converter. Most sensors have a heater so they start working soon after a cold start. A traditional zirconia sensor switches between about 0.1 volt (lean) and 0.9 volt (rich); many newer upstream sensors are wide-band air-fuel sensors that report differently, so check which type your engine uses.
P0133 symptoms
- Check engine light
- Slightly lower fuel economy
- Usually no drivability change
Common causes of P0133
- Aged sensor
- Sensor contaminated by oil, coolant or silicone
- Exhaust leak near the sensor
How to diagnose P0133
- Check for other codes and fix fuel trim problems first
- Watch the sensor switching speed on a scan tool or scope
- Look for oil burning or coolant loss that could contaminate the sensor
Can you drive with P0133?
Yes; it is not urgent, but replace the sensor to keep fuel control accurate.
P0133 tips
A slow sensor is usually just old. Before replacing it, make sure the engine is not burning oil or coolant, which coats sensors and makes new ones fail early. Use an exact-fit sensor and anti-seize only on the threads.
Will P0133 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0133 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0131 | O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1) |
| P0134 | O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1) |
| P0171 | System Too Lean (Bank 1) |
Guides that help
When it is more than a sensor
Oxygen sensor codes are fixed with a sensor, wiring, a fuse or an exhaust leak repair. An engine burning oil or coolant contaminates sensors quickly; if new sensors keep failing, check for blue or white exhaust smoke and a head gasket leak, and compare engines by code on our engines page if the engine is worn out.
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