GM OBD Trouble Code 66

A/C Pressure sensor circuit error (low pressure indicated)

The ECM monitors the A/C system pressure sensor circuit. If the system pressure is to low the ECM will not allow the A/C compressor to operate.

Fault Code Description

  • 66 - A/C Pressure sensor circuit error (low pressure indicated)

Symptoms

  • Poor A/C performance

Common Problems

  • Low refrigerant charge due to system leak
  • Faulty A/C pressure sensor
  • Quick test - On A/C systems with multiple pressure sensors, on a cold engine with the key on and the engine off the scan tool readings for the A/C pressure sensors should all be the same.

Related Questions

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