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P0685



DTC P0685

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.


DTC Descriptor
DTC P0685
- Engine Controls Ignition Relay Control Circuit



Diagnostic Fault Information





Circuit/System Description

The powertrain relay, which is pwr/trn relay 29, is a normally open relay. The relay switch is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the relay switch contact at all times. The powertrain control module (PCM) supplies the ground path to the relay coil control circuit through an output driver module (ODM). The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the PCM. The ignition 1 voltage that is supplied to the PCM provides power for the throttle actuator control (TAC) system. The PCM also monitors the voltage level on the ignition 1 voltage circuit to confirm that the powertrain relay contacts have closed.

Conditions for Running the DTC

* The battery voltage is between 9-18 volts.
* The ignition is ON.
* The powertrain relay has been commanded ON.


Conditions for Setting the DTC

* The commanded state of the ODM does not match and the actual state of the control circuit.
* The condition is present for more than 5 seconds.


Action Taken When the DTC Sets

DTC P0685 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0685 is a Type B DTC.

Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Powertrain Control Module Description (Powertrain Control Module Description)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

1. With the ignition ON, engine OFF, observe the EC Ignition Relay Circuit Status parameter. The parameter should indicate OK.
2. With the ignition ON, engine OFF, probe both test points of all the fuses that are powered by the powertrain relay. The test lamp should illuminate for the fuse test point of the voltage side of each fuse.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.


Circuit/System Testing

1. Ignition OFF, disconnect the powertrain relay, which is pwr/trn relay 29.
2. Ignition ON, verify that a test lamp illuminates between the powertrain relay coil B+ and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the battery positive cable to the underhood fuse block.

3. Ignition OFF, verify that a test lamp does not illuminate between the powertrain relay coil B+ circuit and the control circuit.

• If the test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the PCM.

4. Remove the test lamp.
5. Ignition ON, verify with a scan tool that the powertrain relay EC Ignition Relay Circuit Status parameter is OK.

• If not the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the PCM.

6. Test the coil side of the powertrain relay for 65-110 ohms.

• If not within the specified value, replace the relay.

7. Ignition OFF, disconnect the PCM X1 connector.
8. Test the powertrain relay control circuit X1-24 for an open/high resistance.

• If the circuit tests normal, replace the PCM.

9. Verify that a test lamp does not illuminate between the relay ignition 1 voltage circuit at the powertrain relay and ground.

• If the test lamp illuminates, test the relay ignition 1 voltage circuit for a short to voltage between the powertrain relay and each component powered by the relay.

10. Verify that a test lamp illuminates between the relay switch B+ and ground.

• If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground, or an open/high resistance. If the circuits test normal, and the fuse for the ignition 1 voltage circuit is open, test the ignition 1 voltage circuit for a short to ground.

11. Connect a 20A fused jumper wire between the relay switch B+ and the relay ignition 1 voltage circuit.
12. Ignition ON, engine OFF, probe the ignition voltage circuit for each component powered by the powertrain relay.

• If the test lamp does not illuminate, test the ignition 1 voltage circuit for an open/high resistance.

13. If all circuits test normal, replace the relay.


Repair Instructions

* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for PCM replacement, setup, and programming


Repair Verification

1. Install any components that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
3. Clear the DTCs.
4. Turn OFF the ignition for 60 seconds.
5. Ignition ON, observe the circuit status parameters for each component powered by the powertrain relay. The circuit status parameters should indicate OK.
6. Start the engine. If engine does not run, Refer to Engine Cranks But Does Not Run (Engine Cranks But Does Not Run).
7. If another DTC is present, Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) and perform the appropriate diagnostic procedure.

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