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 C DTCs.

Conditions for Clearing the DTC

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

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

Circuit/System Verification

1. Ignition OFF, allow the ECM to completely power down. Probe both test points of each of the fuses supplied with voltage by the powertrain relay. The test lamp should not illuminate on any test point of any fuse.
2. Ignition ON, probe both test points of each of the fuses supplied with voltage by the powertrain relay. The test lamp should illuminate on at lease one test point of each fuse.

Circuit/System Testing

1. Ignition OFF, disconnect the Powertrain Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the ignition circuit terminal 30 and ground.

⇒	If the test lamp illuminates, test the ignition circuit for a short to voltage.

3. Ignition OFF, verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

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

4. Verify that a test lamp illuminates between the B+ circuit terminal 87 and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.

5. Disconnect the X2 harness connector at the K20 ECM.
6. Test for less than 2 ohms between ground and the following terminals:

•	ECM terminal 1 X2

•	ECM terminal 2 X2

•	ECM terminal 4 X2

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

7. Ignition ON, verify that a test lamp illuminates between connector terminal 54 X2 and ground.

⇒	If the test lamp does not illuminate, test the circuit for an open/high resistance and a short to ground. If the circuit tests normal and its fuse is open, replace the K20 ECM.

8. Ignition OFF, connect the harness connector at the K20 ECM.
9. Ignition ON, connect a jumper wire between the B+ circuit terminal 87 and the ignition circuit terminal 30. Verify that the scan tool communicates and that the EC Ignition Relay Feedback Signal parameter indicates B+ voltage.

⇒	If not the specified value or if the scan tool does not communicate, test the ignition circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

10. Ignition OFF, remove the jumper wire. Allow the K20 ECM to completely power down.
11. Connect a DMM, set on the diode setting, between the control circuit terminal 85 and ground.
12. Ignition OFF, the DMM reading should be greater than 2.5 volts or display Open Loop.

⇒	If less than the specified value, test the control circuit for a short to voltage or short to ground. If the circuits test normal, replace the K20 ECM.

13. Ignition ON, the DMM reading should be less than 1 volt.

⇒	If greater than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

14. If all circuits test normal, replace the Powertrain Relay.

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.