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Home >> Mazda >> 2014 >> MX-5 Miata Club, Automatic Trans >> Repair and Diagnosis >> Engine Performance >> System >> On-Board Diagnostic [Engine Control System LF] >> DTC P0685

DTC P0685

DTC P0685  Main relay control circuit open 
DETECTION CONDITION 
  • This DTC sets when the ignition switch position run circuit indicates the key is in the off, ACC, or LOCK position, and the amount of time the PCM remains powered through the PCM power relay exceeds a predetermined amount of time.

Diagnostic support note 
  • This is a continuous monitor (CCM).
  • The MIL 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 (Mode 2) is available.
  • The DTC is stored in the PCM memory.
POSSIBLE CAUSE 
  • Main relay malfunction
  • PCM malfunction
DIAGNOSTIC PROCEDURE

STEP INSPECTION ACTION
1 VERIFY FREEZE FRAME DATA (MODE 12) HAS BEEN RECORDED 
  • Has the FREEZE FRAME DATA (Mode 12) been recorded?
 Yes Go to the next step.
No Record the FREEZE FRAME DATA (Mode 12) on the repair order, then go to the next step.
2 VERIFY RELATED SERVICE BULLETINS AVAILABILITY 
  • Verify related Service Bulletins availability.
  • Is any related Service Bulletins available?
 Yes Perform the repair or diagnosis according to the available Service Bulletins.
  • If the vehicle is not repaired, go to the next step.
No Go to the next step.
3 INSPECT MAIN RELAY 
  • Turn the ignition switch to oft.
  • Remove the main relay.
  • Inspect the main relay.

    (See RELAY INSPECTION ).

  • Is there any malfunction?
 Yes Replace the main relay, then go to the next step.
No Go to the next step.
4 VERIFY TROUBLESHOOTING OF DTC P0685 COMPLETED 
  • Make sure to reconnect all disconnected connectors.
  • Clear the DTC from the PCM memory using the M-MDS.
  • Start the engine and warm it up completely.
  • Is the PENDING CODE for this DTC present?
 Yes Replace the PCM, then go to the next step.
(See PCM REMOVAL/INSTALLATION ).
No Go to the next step.
5 VERIFY AFTER REPAIR PROCEDURE 
 Yes Go to the applicable DTC inspection.
(See DTC TABLE ).
No DTC troubleshooting completed.
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