P0685
DTC P0685
CIRCUIT DESCRIPTION
The powertrain 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 ODM output control is configured to operate as a low side driver for the powertrain relay. The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the ODM for the powertrain relay to turn OFF, the expected voltage on the relay coil control circuit should be a high voltage condition. When the ECM commands the ODM to turn ON, the expected voltage on the relay coil control circuit should be a low voltage condition. DTC P0685 indicates that the powertrain relay control circuit voltage does not match the commanded state of the ODM. DTC P0685 sets when an open, high resistance, short to ground, or a short to battery positive voltage is detected on the powertrain 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 9-16 volts.
- The ignition switch is turned ON.
- The powertrain relay has been commanded ON.
CONDITIONS FOR SETTING THE DTC
- The commanded state of the ODM and the actual state of the control circuit do not match.
- The condition is present for more than 5 seconds.
ACTION TAKEN WHEN THE DTC SETS
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in Failure Records.
- The driver information center, if equipped, may display a message.
CONDITIONS FOR CLEARING THE MIL/DTC
- A current DTC, last test failed, clears when the diagnostic runs and passes.
- A history DTC clears 40 consecutive warm-up cycles, if this or any other related diagnostic reports no other failures.
- Clear the DTC with a scan tool.
TEST
