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

P0646-00: (PCM - VIN Y) 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	A/C relay malfunction (Refer to RELAY INSPECTION in the 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 applicable PCM REMOVAL/INSTALLATION (VIN Y) in the 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. Perform the DTC inspection for the PCM. (See DTC INSPECTION .)
Courtesy of MAZDA MOTORS CORP.
1	Battery
2	IG1 relay
3	A/C relay
4	PCM