DTC P0685-00; Main Relay Control Circuit Open: Notes

DTC P0685:00	Main relay control circuit open
DETECTION CONDITION	The period of time in which the PCM power supply remains on after the ignition is switched off is not within the specified time. Diagnostic support note This is a continuous monitor (CCM). The check engine light illuminates if the PCM detects the above malfunction condition in two consecutive drive cycles or in one drive cycle while the DTC for the same malfunction has been stored in the PCM. PENDING CODE is available if the PCM detects the above malfunction condition during first drive cycle. FREEZE FRAME DATA/Snapshot data is available. DTC is stored in the PCM memory.
FAIL-SAFE FUNCTION	Not applicable
POSSIBLE CAUSE	Main relay malfunction Short to ground or open circuit in main relay power supply circuit: Short to ground in wiring harness between MAIN 200 A fuse and main relay terminal D MAIN 200 A fuse and/or ENG.MAIN 40 A fuse malfunction Open circuit in wiring harness between battery positive terminal and main relay terminal D ENGINE2 15 A fuse malfunction Short to ground in wiring harness between the following terminals: Main relay terminal C-PCM terminal 2S Main relay terminal C-PCM terminal 2T PCM connector or terminals malfunction Open circuit in wiring harness between PCM terminal 1BZ and body ground Open circuit in wiring harness between PCM terminal 2AA and body ground Open circuit in wiring harness between the following terminals: Main relay terminal C-PCM terminal 2S Main relay terminal C-PCM terminal 2T PCM malfunction

Fig 1: Identifying PCM Wiring Harness Side Connector Terminals (P0685 00)

Courtesy of MAZDA MOTORS CORP.