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GM OBD Trouble Code 64

By Jim Taddei, May 1, 2009

Right bank O2 sensor lean exhaust indicated

MAP sensor circuit signal voltage low (high vacuum indicated)

  • Depending on the model, code 64 can refer to two different systems.
  • Please choose from one of the above links for specific information on each system.

Right bank O2 sensor lean exhaust indicated

The ECM receives a signal from the O2 sensor based on the amount of oxygen in the exhaust. If there is excess oxygen in the exhaust, it is in lean condition and the O2 sensor voltage will be low. The ECM uses this information to adjust the amount of fuel delivered to each cylinder. On V-type engines with two O2 sensors, code 64 would indicate the right bank sensor.

Fault Code Description

  • 64 - Oxygen sensor error (lean condition indicated)

Symptoms

  • Lack of power

Common Problems

  • Faulty O2 sensor
  • Engine vacuum leak

MAP sensor circuit signal voltage low (high vacuum indicated)

The ECM uses the Manifold Absolute Pressure (MAP) sensor as an indication of engine load. High voltage would indicate low engine vacuum and higher engine load. Low voltage would indicate high engine vacuum and lower engine load. The ECM uses the information from this sensor to help calculate fuel delivery and spark timing.

Fault Code Description

  • 64 - MAP sensor circuit error (signal low indicating high vacuum)

Symptoms

  • Poor engine performance
  • Engine running lean (not enough fuel, hard starting, lack of power)

Common Problems

  • GM MAP sensors do not commonly fail
  • Due to erratic engine vacuum, other engine performance problems can cause a code 64 to set

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