DTC P0646-00: A/C Compressor Magnetic Clutch Control System: Low Input

P0646: 00 (PCM (PYUL)) DETECTION CONDITION AND POSSIBLE CAUSE

System malfunction location	A/C compressor magnetic clutch control system: Low input
Detection condition	The A/C compressor magnetic clutch control voltage is less than the standard relative to the PCM control signal.
Fail-safe	Release the magnetic clutch.
Possible cause	IG1 relay malfunction (Refer to [RELAY INSPECTION ] in service information). A/C relay malfunction (Refer to [RELAY INSPECTION ] in service information). Malfunction in wiring harness (including connector/terminal) between IG1 relay and A/C relay (See CIRCUIT INSPECTION .) (See CONNECTOR INSPECTION .) Malfunction in wiring harness (including connector/terminal) between A/C relay and PCM (See CIRCUIT INSPECTION .) (See CONNECTOR INSPECTION .) PCM malfunction (Refer to [PCM REMOVAL/INSTALLATION ] in service information).
Repeatability verification procedure	Clear the DTC recorded in the memory. (See CLEARING DTC .) Set the A/C temperature control to MAX COLD. Turn the A/C switch on to operate the air conditioner. Verify that cold air is flowing from the air vent.
Courtesy of MAZDA MOTORS CORP.
1	Battery
2	IG1 relay
3	A/C relay
4	PCM