Diagnostic Instructions

DTC Descriptors

DTC P0685: Engine Controls Ignition Relay Control Circuit

DTC P0686: Engine Controls Ignition Relay Control Circuit Low Voltage

DTC P0687: Engine Controls Ignition Relay Control Circuit High Voltage

DTC P0689: Engine Controls Ignition Relay Feedback Circuit Low Voltage

DTC P0690: Engine Controls Ignition Relay Feedback Circuit High Voltage

Diagnostic Fault Information

Important: A condition with the main relay will set multiple DTCs. The DTCs listed in the table will only set if a condition exists with the main relay.

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
B+ Supply Voltage - Coil	P0685	P0685	P0685	--	--
B+ Supply Voltage - Switch	--	P0689	P0689	P0690	--
Relay Control Circuit	P0686	P0685	P0685	P0687	P0685
Ignition Voltage Circuit	--	P0689	P0689	P0690	--

Circuit/System Description

The engine controls (EC) ignition relay, or main relay 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 switch 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. When the ECM commands the relay ON, ignition voltage is supplied to the following fuses in the underhood fuse block:

Conditions for Running the DTC

P0685, P0686, and P0687

P0689 and P0690

Conditions for Setting the DTC

P0685, P0686, and P0687

The commanded state of the ODM and the actual state of the control circuit do not match for greater than 50 seconds.

P0689 and P0690

The ECM detects that main relay feedback voltage is less than predicted range for greater than 1 second, when the powertrain relay is commanded ON or OFF.

Action Taken When the DTC Sets

DTCs P0685, P0686, P0687, P0689, and P0690 are Type C DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0685, P0686, P0687, P0689, and P0690 are Type C DTCs.

Diagnostic Aids

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, you should be able to communicate with the ECM using a scan tool.
2. Ignition ON, view the DTC information with a scan tool. DTCs P0685, P0686, P0687, P0689, or P0690 should not be set.
3. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

1. Ignition OFF, disconnect the main relay.
2. Verify a test lamp illuminates between the relay coil B+ circuit terminal 85 and ground.

⇒	If the test lamp does not illuminate, repair the B+ voltage circuit for a short to ground or an open/high resistance.

3. Ignition OFF, connect a test lamp between the relay coil control circuit terminal 86 and the relay coil B+ voltage circuit terminal 85. The test lamp should not be illuminated.

⇒	If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.

4. Ignition ON. The test lamp should turn ON.

⇒	If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the ECM.

5. Connect a 20A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay switch ignition voltage circuit terminal 87.
6. Attempt to start the engine. The engine should start.

⇒	If the engine does not start, test the ignition voltage circuit between the main relay and the ECM for a short to ground or for an open/high resistance. If the circuit/connections test normal, replace the ECM.

7. If all circuits/connections test normal, test or replace the main relay.

Component Testing

1. Test for 70-110 ohms between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the main relay.

2. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If continuity is detected, replace the main relay.

3. Install a 10A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

⇒	If greater than the specified range, replace the main relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.