MasterTuning Fault code dictionary (DTC)

P0133 — O2 sensor: slow response (bank 1 sensor 1)

Severity: Warning Can you drive? Yes, no known limitation Make: All makes (OBD-II standard)
MeaningThe sensor ahead of the catalyst reacts too slowly to mixture changes. It is not broken: it is aged, and the ECU can no longer trim with the required precision.
FamilyPowertrain (P)

Typical symptoms

Higher fuel consumption
Slightly rough idle
Engine warning light on
Problems at the emissions test

Common causes

Sensor aged by mileage or contamination
Exhaust leak upstream of the sensor
Burnt oil or coolant poisoning the sensor
Weak sensor heater
Additives or poor quality fuel

What to do

The upstream sensor is a wear item: replacement after 120-150,000 km is normal. First check for exhaust leaks upstream, otherwise the new sensor will read just as falsely as the old one.

Frequently asked questions

What does code P0133 mean?

O2 sensor: slow response (bank 1 sensor 1). The sensor ahead of the catalyst reacts too slowly to mixture changes. It is not broken: it is aged, and the ECU can no longer trim with the required precision.

Can I keep driving with code P0133 active?

Yes, no known limitation

Common causes — P0133

Sensor aged by mileage or contamination Exhaust leak upstream of the sensor Burnt oil or coolant poisoning the sensor Weak sensor heater Additives or poor quality fuel

How do you fix code P0133?

The upstream sensor is a wear item: replacement after 120-150,000 km is normal. First check for exhaust leaks upstream, otherwise the new sensor will read just as falsely as the old one.

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