P0685
DTC P0685
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 powertrain control module (PCM) 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 PCM. When the PCM commands the relay ON, the expected voltage on the relay coil control circuit should be a low voltage condition. If the fault detection circuit measures a high voltage condition, DTC P0685 will set. DTC P0685 indicates a short to battery positive voltage, or ignition 1 voltage on the main relay coil control circuit.
DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
- DTC P0685 Computers and Control Systems Ignition Relay Control Circuit
CONDITIONS FOR RUNNING THE DTC
- The battery voltage is between 11 and 18 volts
- The ignition is ON.
- The diagnostic runs continuously when the above conditions are met.
CONDITIONS FOR SETTING THE DTC
The PCM detects more than 4.6 volts on the relay coil control circuit for more than 2 seconds.
ACTION TAKEN WHEN THE DTC SETS
- The PCM will not illuminate the malfunction indicator lamp (MIL) if this diagnostic runs and fails.
- The engine will crank, but will not run.
- The Class II communications will be available with the use of a scan tool.
CONDITIONS FOR CLEARING THE DTC
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.
DIAGNOSTIC AIDS
The DTC P0685 diagnostic table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test in Starting and Charging. Battery Inspection/Test
TEST
