Emission control
P0133 — O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
The upstream oxygen sensor on bank 1 reacts too slowly to changes in the exhaust mixture. A slow sensor makes fuel control sluggish and increases emissions.
Common causes
- Aged or contaminated oxygen sensor
- Exhaust leak before or near the sensor
- Silicone, oil or coolant contamination
- Wiring or connector problem
- Fuel system or misfire problems
Symptoms
- Reduced fuel economy
- Slightly rough running
- Check engine light
- Failed emissions test
How to check
- Check for exhaust leaks around the manifold and sensor
- Check for misfire and fuel trim problems
- Graph the sensor on a scan tool and measure how quickly it switches
- Replace the sensor if it responds slowly with healthy mixture
Can you keep driving?
Drivable; the effect is mainly on fuel use and emissions. Repair it at the next service.
Related codes
Frequently asked questions
- What does P0133 mean?
- The oxygen sensor is not switching between rich and lean fast enough.
- Do oxygen sensors wear out?
- Yes. They age with mileage and contamination, so slow response is a common sign of a worn sensor.
General reference information. It does not replace a diagnosis on your own vehicle. The same code can have different causes depending on make, model year and engine; check the manufacturer's documentation or ask a technician with a scan tool.