GM OBD Trouble Code 45

Oxygen Sensor Error (Rich Condition Indicated)

The ECM receives a signal from the O2 sensor based on the amount of oxygen in the exhaust. If there is little oxygen in the exhaust, it is in rich condition and the O2 sensor voltage will be high. The ECM uses this information to adjust the amount of fuel delivered to each cylinder.

Fault Code Description

  • 45 - Oxygen sensor error (rich condition indicated)
  • On V-type engines with two O2 sensors, code 45 would indicate the left bank sensor is rich


  • Black smoke from exhaust

Common Problems

  • Faulty O2 sensor
  • Leaking fuel injector or fuel pressure regulator

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