P0646 OBD II Trouble Code A/C Clutch Relay Control Circuit Low

How to quickly diagnose and repair, and causes of a P0646 electrical code which indicates a low voltage situation within the A/C air conditioning clutch relay control circuit.

Symptoms of P0646 OBD II Trouble Code

  • A/C functioning poorly
  • A/C not working at all
  • Check engine light illuminated

Common Causes of P0646 OBD II Trouble Code

  • Faulty A/C clutch relay
  • Defective A/C clutch
  • Broken control module ground strap
  • Defective control module
  • Blown fuse or fuse-able link (if applicable)
  • Corroded or damaged connector
  • Low or over serviced A/C system
  • Faulty or damaged wiring
  • Faulty A/C Compressor
  • Faulty PCM

Severity of P0646 OBD II Trouble Code

The severity of this code can vary from just an illuminated check engine light with the air conditioning working fine to it running poorly or not at all.