66 A/C Pressure Sensor Circuit Low Pressure Indicated

Make
GM (1982-1995)
Category
Powertrain - Computer and Auxiliary Controls
Severity
Check Engine Light
Applies to
1990-1995 Corvette, Camaro, Lumina, C/K trucks

How to read it

Code 66 reads as 6 flashes, pause, 6 flashes on the check-engine light. Jump terminals A and B on the ALDL connector with the key off, then turn the key on with the engine off and count the check-engine flashes.

What does GM code 66 mean?

66. A/C Pressure Sensor Circuit Low Pressure Indicated. This code sets when your vehicle computer detects a/c pressure sensor circuit low pressure indicated.

Common causes of 66

How to fix 66

  1. Read codes with an ALDL scan tool
  2. Compare sensor reading with manifold gauge pressure
  3. Inspect the sensor connector and wiring
  4. Check system charge before condemning the sensor
  5. Replace the sensor if gauges read normal but signal reads low
  6. Evacuate and recharge only after the leak is fixed

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