P0685

DTC P0685 or P0690

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy 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 Descriptors
DTC P0685
- Engine Controls Ignition Relay Control Circuit

DTC P0690
- Engine Controls Relay Feedback Circuit High Voltage




Diagnostic Fault Information






Typical Scan Tool Data






Circuit/System 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). The 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 powertrain relay ON, ignition 1 voltage is supplied to the ECM, and to several additional circuits.


Conditions for Running the DTC


P0685
* The ignition is ON.
* The battery voltage is between 9-16 volts.



P0690
* This DTC will run with the ignition ON or OFF.
* This DTC will run when the powertrain relay is commanded ON or OFF.
* DTC P0685 is not set.



Conditions for Setting the DTC


P0685
* 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.



P0690
* The ECM detects more than 16 volts on the ignition 1 voltage circuit to the ECM when the relay is commanded ON.
* The ECM detects more than 2 volts on the ignition 1 voltage circuit to the ECM when the relay is commanded OFF.
* The condition is present for more than 2 seconds.



Action Taken When the DTC Sets

DTCs P0685 and P0690 are Type B DTCs.


Conditions for Clearing the DTC

DTCs P0685 and P0690 are Type B DTCs.


Diagnostic Aids

This test procedure requires that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test (Battery Inspection/Test) .


Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Circuit Testing (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
* Connector 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
Special Tools

* J 35616 GM-Approved Terminal Test Kit
* J 43244 Relay Puller Pliers



Circuit/System Verification

1. Engine running, command the powertrain relay ON and OFF, with a scan tool, while observing the following powertrain relay coil control circuit status parameters.

* EC Ign. Relay Ckt. Short Gnd Test Status
* EC Ign. Relay Ckt. Open Test Status
* EC Ign. Relay Ckt. Short Volts Test Status
Each parameter should toggle between OK and Not Run.

2. Ignition ON, engine OFF, with a test lamp, probe both test points of all the fuses that are powered by the powertrain relay. The test lamp should illuminate ON for at least one test point 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


Important: You must perform the Circuit/System Verification first.


1. Ignition OFF, disconnect the Ign 1 relay.
2. Ignition ON, verify that a test lamp illuminates between the Ign 1 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 Ign 1 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 ECM.

4. Remove the test lamp.
5. Command the engine control ignition relay ON, with a scan tool. Verify with a scan tool that the EC Ign 1 Relay Ckt. Short Volts Test 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 ECM.

6. Test the coil side of the Ign 1 relay for 65-110 ohms.

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

7. Ignition OFF, disconnect the ECM X1 connector.
8. Test the Ign 1 relay control circuit for an open/high resistance.

• If the circuit tests normal, replace the ECM.

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

• If the test lamp illuminates, test the relay ignition 1 voltage circuit for a short to voltage. If the circuit tests normal, replace the ECM.

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 to the ECM for a short to ground. If the circuit tests normal, replace the ECM.

11. Connect a 20 A fused jumper wire between the relay switch B+ and the relay ignition 1 voltage circuit.
12. Ignition ON, engine OFF, monitor the EC Ignition Relay Feedback parameter with a scan tool. The parameter should display B+.

• If the parameter does not display B+, test the ignition 1 voltage circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

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



Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.


Control Module References (Programming and Relearning) for ECM replacement, setup, and programming