Trouble CodesGM OBD Trouble CodesGM Code 34

CODE 34 - MAP Sensor or MAF Sensor depending on the enigne

Trouble Code 34 indicates that the Mass Air Flow (MAF) sensor is reporting less air is entering the engine than makes sense based on RPM and TPS. The MAF sensor produces a frequency output; around 30 Hz at idle to 150 Hz under acceleration. The frequency varies proportionally to airflow. The ECM monitors the frequency and thus determines airflow into the engine. Typical idle MAF is 5 to 7 grams per second.

The conditions for setting this code are:

  • no Code 21 or 22 (TPS Error) present, and
  • the air flow reported is < 4 grams per second, and
  • TPS indicates 10% or more throttle position, and
  • the engine speed is 1800 RPM or higher, and
  • the above conditions exist for over 5 seconds.


Typical causes for this code include:

1) Faulty air ducting to or from MAF sensor
2) Faulty ECM-to-MAF connections
3) Poor routing of MAF harness (i.e. near coil packs)
4) Maladjusted TPS sensor
5) Defective MAF sensor
6) Defective ECM


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