P0646 OBD-II: A/C Clutch Relay Control Circuit Low

P0646 Severity

Moderate

Will P0646 go away on its own?

Once the vehicle's onboard system no longer detects the issue, most codes will disappear on their own. If your vehicle still has this code, however, it should be properly diagnosed to avoid a more serious problem.

For a proper diagnosis, RepairPal Certified shops have the equipment, tools, and expertise.

Moderate severity codes might not threaten the vehicle's safety or functionality immediately, but you should still get it diagnosed within a reasonable time frame to keep your car running well.

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P0646 Summary Find a Repair Shop P0646 Details Ask RepairPal CarGenius Other OBD-II Codes

What causes OBD-II fault code P0646?

The engine control module (PCM) uses a relay to control voltage to the A/C Compressor Clutch. The A/C clutch engages, allowing the Air Conditioning system to operate. When the PCM is unable to control the relay, code P0646 will set.

OBD II Fault Code

OBD II P0646

OBD-II Code A/C may not operate is defined as a A/C Clutch Relay Control Circuit Low

A/C may not operate Symptoms

A/C may not operate

Common Problems That Trigger the P0646 Code

A/C compressor failure
A/C compressor relay failure
Powertrain Control Module (PCM) failure
Wiring issue

Common Repairs Needed for the P0646 Code

AC Compressor Replacement

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Other OBD-II Codes

P0645: A/C Clutch Relay Control Circuit P0644: Driver Display Serial Communication Circuit P0643: Sensor Reference Voltage "A" Circuit High P0642: Sensor Reference Voltage "A" Circuit Low P0641: Sensor Reference Voltage "A" Circuit/Open P0640: Intake Air Heater Control Circuit P063F: Auto Configuration Engine Coolant Temperature Input not Present P063E: Auto Configuration Throttle Input not Present P063D: Generator Voltage Sense Circuit High P063C: Generator Voltage Sense Circuit Low P063B: Generator Voltage Sense Circuit Range/Performance P063A: Generator Voltage Sense Circuit P0647: A/C Clutch Relay Control Circuit High P0648: Immobilizer Lamp Control Circuit P0649: Speed Control Lamp Control Circuit P064A: Fuel Pump Control Module P064B: PTO Control Module P064C: Glow Plug Control Module P064D: Internal Control Module O2 Sensor Processor Performance P064E: Internal Control Module O2 Sensor Processor Performance P064F: Unauthorized Software/Calibration Detected P0650: Malfunction Indicator Lamp (MIL) Control Circuit P0651: Sensor Reference Voltage "B" Circuit/Open P0652: Sensor Reference Voltage "B" Circuit Low

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