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EmissionsSeverity Low: usually safe to drive

P0133O2 Sensor Circuit Slow Response (bank 1 sensor 1)

What it means

The oxygen sensor bank 1 sensor 1 switches between rich and lean more slowly than the ECU expects. The sensor is usually aged or contaminated. The upstream sensor (before the catalyst) is what the ECU uses to correct the mixture.

Symptoms

  • Check engine light
  • Higher fuel consumption
  • Possibly a rough idle or failed emissions test

Common causes

  • Aged or contaminated oxygen sensor
  • Exhaust leak near the sensor
  • Heater circuit fault keeping the sensor too cold
  • Engine burning oil or coolant

What to check first

  1. Scope the sensor at 2,500 rpm: rich-to-lean transition should take under about 300 ms
  2. Check the heater circuit
  3. Check for exhaust leaks and signs of oil or coolant contamination
Can I drive with P0133? Usually yes. P0133 rarely affects how the car drives, but it keeps the check engine light on and can fail an emissions test.
Practise it: Lazy oxygen sensor in the engine simulator shows this fault in live data, tests and on the scope.Open in the simulator

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0133

Oxygen (lambda) sensorWiring, typical values, multimeter and scope tests

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P0133: questions and answers

What does P0133 mean?

P0133: O2 Sensor Circuit Slow Response (bank 1 sensor 1). The oxygen sensor bank 1 sensor 1 switches between rich and lean more slowly than the ECU expects. The sensor is usually aged or contaminated. The upstream sensor (before the catalyst) is what the ECU uses to correct the mixture.

What are the symptoms of P0133?

Check engine light. Higher fuel consumption. Possibly a rough idle or failed emissions test.

What causes P0133?

Aged or contaminated oxygen sensor. Exhaust leak near the sensor. Heater circuit fault keeping the sensor too cold. Engine burning oil or coolant.

How do you diagnose P0133?

1. Scope the sensor at 2,500 rpm: rich-to-lean transition should take under about 300 ms 2. Check the heater circuit 3. Check for exhaust leaks and signs of oil or coolant contamination

Can I drive with P0133?

Usually yes. P0133 rarely affects how the car drives, but it keeps the check engine light on and can fail an emissions test.