P0685

DTC P0685: Engine Controls Ignition Relay Control Circuit

Wiring Diagram:

Circuit Description
The main relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature contact at all times. The Engine Control Module (ECM) supplies the ground path to the relay coil control circuit via an internal integrated circuit, called an Output Driver Module (ODM). One of the ODM output circuits is configured to operate as a low side driver for the main relay. The low side driver also incorporates a fault detection circuit, which is continuously monitored by the ECM.

Conditions for Setting the DTC
^ Engine is running.
^ Ignition voltage is between 11 and 16 V.
^ The ECM detects an open, a short to ground, or a short to battery condition in the main relay control circuit.

Action Taken When the DTC Sets
^ The Malfunction Indicator Lamp (MIL) will illuminate.
^ The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
^ A history DTC is stored.

Conditions for Clearing the MIL/DTC
^ A history DTC will clear after 40 consecutive warm up cycles without a fault.
^ The DTC(s) can be cleared by using the scan tool.
^ Disconnecting the ECM battery feed for more than 10 seconds.

Diagnostic Aids
The DTC P0685 diagnostic table assumes that the vehicle battery is fully charged.

Step 1 - 5:

Step 6 - 14:

Step 15 - 18:

Troubleshooting