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	P0685	P0685	P0685	--	--
Relay Control Circuit	P0685	P0685	P0685	P0685	--

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 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

Conditions for Clearing the DTC

Diagnostic Aids

Reference Information

Schematic Reference

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

Special Tools

J 43244 Relay Puller Pliers

Circuit/System Verification

1. Ignition ON, verify that the Feedback Circuit parameter indicates B+ voltage.
2. Ignition ON, command the powertrain relay ON and OFF. Listen or feel to verify that the powertrain relay turns ON and OFF with the commanded states.

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 relay coil voltage supply circuit terminal 85 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 terminal 86 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 terminal 85 and the relay coil control circuit terminal 86. Use a scan tool to command the powertrain relay 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 or a faulty ECM.

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

5. Measure for B+ between the relay armature supply circuit terminal 30 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 ETC fuse.

⇒	If voltage is present, test the ignition 1 voltage circuit between the ECM, the powertrain relay, and the ETC 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 30 and the ignition 1 voltage terminal 87 of the powertrain relay at the underhood fuse block. With a test lamp, probe both test points of the ETC fuse.

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

8. With a test lamp, test for voltage on both test points of the following fuses:

•

ETC Fuse

•	Emission 1 Fuse

⇒	If the test lamp fails to illuminate on one test point of each fuse, repair the open or high resistance between the fuse and the powertrain relay. All wire circuit resistance should measure 2 ohms or less.

Component Testing

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.