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EmissionsSeverity Medium: diagnose soon

P0151O2 Sensor Circuit Low Voltage (bank 2 sensor 1)

What it means

The oxygen sensor bank 2 sensor 1 stays at a low voltage (lean reading) for too long. 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

  • Real lean condition (vacuum leak, low fuel pressure)
  • Exhaust leak upstream of the sensor drawing in air
  • Signal wire shorted to ground
  • Failed sensor

What to check first

  1. Check fuel trims: if they are high, look for the cause of the lean mixture first
  2. Propane-enrich the intake: a good sensor goes above 0.8 V
  3. Check for exhaust leaks and the sensor wiring
Can I drive with P0151? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

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

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P0151: questions and answers

What does P0151 mean?

P0151: O2 Sensor Circuit Low Voltage (bank 2 sensor 1). The oxygen sensor bank 2 sensor 1 stays at a low voltage (lean reading) for too long. The upstream sensor (before the catalyst) is what the ECU uses to correct the mixture.

What are the symptoms of P0151?

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

What causes P0151?

Real lean condition (vacuum leak, low fuel pressure). Exhaust leak upstream of the sensor drawing in air. Signal wire shorted to ground. Failed sensor.

How do you diagnose P0151?

1. Check fuel trims: if they are high, look for the cause of the lean mixture first 2. Propane-enrich the intake: a good sensor goes above 0.8 V 3. Check for exhaust leaks and the sensor wiring

Can I drive with P0151?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.