P0155: O2 sensor heater circuit, bank 2 sensor 1

The heater in the upstream oxygen sensor on bank 2 has a circuit fault. The sensor is slower after a cold start, and consumption may rise.

Likely causes, most common first

  • Failed heater in the sensor
  • Blown fuse or relay
  • Damaged wiring
  • Corroded connector

Parts usually involved

  • Oxygen sensor
  • Fuse
  • Sensor connector

Test before you replace

Measure heater resistance and check for power and ground at the connector.

General guidance for generic OBD2 codes. Always follow the maker's procedure for the car in front of you.

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