Diagnostic Instructions

DTC Descriptors

DTC P0685: Engine Controls Ignition Relay Control Circuit

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	P1516, P1682, P2101	P0685	P1682, P1516, P2101	--	--
Battery Supply Voltage - Armature	--	P1516, P1682, P2101	P1516, P1682, P2101	--	--
Powertrain Relay Control Circuit	P0690	P0685	P1516, P1682, P2101	P0685, P1516, P1682, P2101, P2176	--
IGN 1 Voltage Circuit	--	P1516, P1682, P2101	P1682, P1516, P2101	--	--

Typical Scan Tool Data

EC Ignition Relay Feedback Signal

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Ignition ON, with the engine OFF Parameter Normal Range: 11.9-12.9 V
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	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 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 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 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

P0690

Conditions for Setting the DTC

P0685

P0690

Action Taken When the DTC Sets

DTCs P0685 and P0690 are Type A DTCs.

Conditions for Clearing the DTC

DTCs P0685 and P0690 are Type A DTCs.

Diagnostic Aids

Reference Information

Schematic Reference

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 43244 Relay Puller Pliers

Circuit/System Verification

1. With the ignition ON, engine OFF, command the engine control ignition relay ON and OFF several times using the scan tool output control function. You should either hear or feel the relay click with each command.
2. With the ignition ON, engine OFF, probe both test points of each of the fuses supplied with voltage by the powertrain relay.

⇒	The test lamp should illuminate on at least one test point of each fuse. If the test lamp does not illuminate continue with Circuit/System Testing.

3. Engine running, observe the DTC information with a scan tool. DTCs P0685 or P0690 should not set.
4. 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. With the ignition OFF, remove the powertrain relay from the underhood fuse block.
2. With the ignition ON, measure for battery positive voltage, B+, between the battery supply voltage coil circuit terminal R48 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 powertrain relay 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 supply voltage coil terminal R48 and the powertrain relay control circuit terminal R50. Use a scan tool to command the powertrain relay ON and OFF using the Engine Controls Ignition Relay selection. 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 powertrain relay control circuit or a faulty ECM.

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

5. Measure for B+ between the relay battery supply voltage switch circuit terminal R47, 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 V8 ECM fuse.

⇒	If voltage is present, test the ignition 1 voltage circuit between the V8 ECM, the powertrain relay, and the V8 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 R47 and the ignition 1 voltage terminal R49 of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the V8 ECM fuse.

⇒	If the test lamp illuminates at both test points of the V8 ECM fuse, repair the ignition 1 voltage circuit between the V8 ECM fuse and the ECM for an open, high resistance, or a faulty ECM. All wire circuit resistance should measure less than 2 ohms.

⇒	If the test lamp only illuminates at one test point of the V8 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 V8 ECM fuse, repair the open or high resistance between the powertrain relay and the V8 ECM fuse. All wire circuit resistance should measure 2 ohms or less.

Component Testing

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for ECM replacement, setup, and programming.