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

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
Battery Supply Voltage - Coil	P0685	P0685	P0685	--	--
Battery Supply Voltage - Armature	P0689	P0689	P0689	--	--
Relay Control Circuit	P0685	P0685	P0685	P0685	--
Relay Feedback Circuit	P0689	P0689	P0689	P0690	--

Typical Scan Tool Data

EC Ignition Relay Feedback Signal

Circuit	Normal Range	Short to Ground	Open	Short to Voltage
Operating Conditions: Ignition ON, with the engine OFF
Battery Supply Voltage - Coil	--	0 V	0 V	--
Battery Supply Voltage - Armature	--	0 V	0 V	--
EC Ignition Relay Control	--	0 V	0 V	--
EC Ignition Relay Feedback	11.9-12.9 V	0 V	0 V	More than 2 V¹
¹ DTC P0690 will set if the ECM detects voltage when the ignition is in the OFF position.

Circuit/System Description

The powertrain/engine controls (EC) ignition 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 relay switch contact at all times. The engine control module (ECM) supplies the ground path to the relay coil control circuit through an output driver module (ODM). The ODM for the relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the relay ON, ignition 1 voltage is supplied to fuses in the underhood fuse block.

The ignition 1 voltage that is supplied to the ECM, provides power to the internal ECM circuits associated with the throttle actuator control (TAC) operation. The ECM 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

P0685 and P0686

P0687, P0689, and P0690

Conditions for Setting the DTC

Action Taken When the DTC Sets

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

Conditions for Clearing the DTC

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

Diagnostic Aids

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Engine Control Module Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Circuit/System Verification

With the ignition ON, engine OFF, probe both test points of each of the fuses supplied with voltage by the powertrain relay.

Circuit/System Testing

1. Ignition OFF, remove the powertrain relay from the underhood fuse block.
2. Ignition ON, measure for battery positive voltage, B+, between the relay coil voltage supply circuit and ground.

⇒	If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay coil. All wire circuit resistance should measure less than 2 ohms.

3. Measure for voltage between the relay coil control circuit and ground.

⇒	If voltage is measured on the control circuit of the relay, test for a short to voltage.

4. Connect a test lamp between the battery positive voltage supply circuit of the relay coil and the relay coil control circuit. Turn the ignition switch ON and OFF. The test lamp should turn ON and OFF when toggling between the commanded states.

⇒	If the test lamp stays ON all the time, test for a short to ground on the relay coil control circuit. If the circuit tests normal, replace the ECM.

⇒	If the test lamp stays OFF all the time, test for an open or high resistance on the relay coil control circuit. All wire circuit resistance should measure less than 2 ohms. If the circuit tests normal, replace the ECM.

5. Measure for B+ between the relay armature supply circuit, and ground.

⇒	If the voltage measures less than B+, repair the open or high resistance in the circuit to the relay armature. All wire circuit resistance should measure less than 2 ohms.

6. With the ignition ON, test for voltage on each test point of the ECM fuse.

⇒	If voltage is present, test the ignition 1 voltage circuit between the ECM, the powertrain relay, and the ECM fuse for a short to voltage.

⇒	If both circuits test normal, replace the ECM.

7. Connect a 20A fused jumper wire between the B+ terminal and the ignition 1 voltage terminal of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ECM fuse.

⇒	If the test lamp illuminates at both test points of the ECM fuse, repair the ignition 1 voltage circuit between the powertrain relay and the ECM for an open or high resistance. If the circuit tests normal, replace the ECM. All wire circuit resistance should measure less than 2 ohms.

⇒	If the test lamp only illuminates at one test point of the ECM fuse, repair the short to ground in the ignition 1 voltage circuit between the fuse and the applicable component. Replace the fuse, as necessary.

⇒	If the test lamp does not illuminate on either test point of the ECM fuse, repair the open or high resistance between the powertrain relay and the ECM fuse. All wire circuit resistance should measure 2 ohms or less.

Component Testing

1. Measure for 70-110 ohms of resistance between terminals 85 and 86 of the main relay.

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

2. Measure for infinite resistance between following terminals and the main relay:

•	Terminals 30 and 86

•	Terminals 30 and 87

•	Terminals 30 and 85

•	Terminals 85 and 87

⇒	If continuity is detected, replace the main relay.

3. Connect a 20A 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. Measure for less than 2 ohms between terminals 30 and 87 of the relay.

⇒	If the resistance measures more than 2 ohms, replace the main relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.