P0151 O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

Powertrain Severity: Moderate Generic OBD-II

The upstream (before the catalytic converter) oxygen sensor, Bank 2 Sensor 1, stays at low voltage, which reads as lean.

Common causes

  • Exhaust or vacuum leak
  • Faulty sensor
  • Signal wire shorted to ground

Symptoms

  • Check engine light
  • Possible hesitation

What to check

  1. Look for exhaust leaks upstream of the sensor
  2. Check fuel trims
  3. Inspect wiring

Manufacturers may add their own detail to generic codes. If your vehicle shows a different description for P0151, follow the service information for that make and model.

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