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

Severity: Medium With a steady light and normal running, arrange diagnosis soon. Stop for a flashing light, severe misfire, overheating, or a glowing catalyst; do not assume those symptoms are only a sensor fault.

What does P0151 mean?

Bank 2 sensor 1 is reporting a persistently low oxygen-signal voltage. The exhaust may truly be lean, or wiring and exhaust leakage may be making the computer see a false lean condition.

Generic OBD-II definition: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1). Confirm applicability in your vehicle service information.

Common causes

  • Signal shorted to ground or high-resistance connection
  • Exhaust leak before the bank 2 sensor
  • Faulty sensor or actual lean fueling

Symptoms

  • Check engine light
  • Possible hesitation
  • May have no obvious symptom

Diagnostic focus

Compare bank 1 and bank 2 fuel trims. A common fuel-supply problem often affects both banks; a one-bank low reading warrants closer inspection of that bank's leaks and wiring.

Can I keep driving with P0151?

Severity: Medium With a steady light and normal running, arrange diagnosis soon. Stop for a flashing light, severe misfire, overheating, or a glowing catalyst; do not assume those symptoms are only a sensor fault.

If the check engine light is flashing or the car runs badly, stop driving and have it checked.

Typical fixes

  • Check for bank 2 lean codes and exhaust leakage
  • Inspect signal and sensor-return connections
  • Have sensor response tested against a known mixture change

Related codes

P0150
O2 Sensor Circuit Malfunction (Bank 2 Sensor 1)P0152
O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)P0174
System Too Lean (Bank 2)

Sources & review

Definitions and diagnostic background checked 2026-11-06. Generic guidance, not a substitute for the service procedure for your exact year, engine, and transmission.