DTC P0685: ECM/Pcm Power Relay Control Circuit/Open: Notes
1. -
DTC detecting condition:
Detected when two consecutive driving cycles with fault occur.
Wiring diagram:
Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .
Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .
After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .
- CHECK ECM CONNECTOR
.
Check the connecting condition of ECM connector.
Is the ECM connector correctly connected?
Yes: Go to 2 .
No: Connect the ECM connector correctly.
- CHECK HARNESS BETWEEN ECM AND M/B (MAIN RELAY) (SHORT TO GROUND)
.
- Turn the ignition switch to OFF.
- Remove the main relay.
- Disconnect the connector from ECM.
- Measure the resistance between the ECM connector and engine ground.
Connector and terminal
(B61) No. 49 - Engine ground:
Is the resistance 1 MΩ or more?
Yes: Go to 3 .
No: Repair the short circuit to ground in harness between ECM connector and M/B (main relay).
- CHECK HARNESS BETWEEN ECM AND M/B (MAIN RELAY) (SHORT TO POWER SUPPLY)
.
- Turn the ignition switch to ON.
- Measure the voltage between ECM connector and engine ground.
Connector and terminal
(B61) No. 13 (+) - Engine ground (-):
(B61) No. 26 (+) - Engine ground (-):
Is the voltage 10 V or more?
Yes: Repair the short circuit to power supply in harness between ECM connector and M/B (main relay).
No: Go to 4 .
- CHECK MAIN RELAY
.
- Turn the ignition switch to OFF.
- Check the main relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>MAIN RELAY .
Is the check result OK?
Yes: Repair the poor contact of ECM connector.
No: Replace the main relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>MAIN RELAY .