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 more than 50 seconds.

P0689 and P0690

The ECM detects that main relay feedback voltage is less than predicted range for more 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

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

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. If the vehicle passes the Circuit/System Verification test, operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

Circuit/System Testing

1. Ignition OFF, disconnect the main relay.

Important: The test lamp is used to load the circuit and may not illuminate.

2. Connect a test lamp between the B+ supply circuit to the coil side of the main relay and the negative terminal of the battery.
3. Ignition ON, test for less than 0.1 volts between the B+ voltage circuit of the main relay and the positive battery terminal.

⇒	If greater than 0.1 volts, repair the B+ voltage circuit to the coil side of the main relay for a short to ground or an open/high resistance.

Important: The test lamp is used to load the circuit and may not illuminate.

4. Connect a test lamp between the B+ voltage supply circuit to the switch side of the main relay and the negative terminal of the battery.
5. Ignition ON, test for less than 0.1 volts between the B+ voltage circuit of the main relay and the positive battery terminal.

⇒	If greater than 0.1 volts, repair the B+ voltage circuit to the switch side of the main relay for a short to ground or an open/high resistance.

6. Ignition OFF, connect a test lamp between the control circuit of the main relay and the B+ voltage supply circuit to the coil side of the main relay.
7. Ignition ON, the test lamp should turn ON when the ignition switch is cycled ON and OFF when the ignition switch is cycled OFF.

⇒	If the test lamp remains ON all the time, test for a short to ground on the control circuit. If the circuit/connections test normal, replace the ECM.

⇒	If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM.

Important: The ignition voltage circuit is between the main relay and the ECM. The ignition voltage circuit is a feedback circuit.

8. Connect a 15A fused jumper wire between the B+ supply voltage circuit and the ignition voltage circuit of the main relay.
9. 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.

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

Component Testing

1. Test for 70-110 ohms of resistance 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. Connect a 15A fused jumper wire from the positive terminal of the battery to relay terminal 85. Connect a jumper wire from the negative terminal of the battery to relay terminal 86. Test for less than 2 ohms of resistance 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.