For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | Diagnostic Procedure Instructions provides an overview of each diagnostic category.

### 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

• | The battery voltage is between 10.5-18 V.

• | The ignition is ON.

• | The relay has been commanded ON.

• | These DTCs run continuously when the above conditions have been met.

#### P0687, P0689, and P0690

• | The battery voltage is between 10.5-18 V.

• | The ignition is OFF.

• | The powertrain relay has been commanded OFF.

• | These DTCs run continuously when the above conditions have been met.

### Conditions for Setting the DTC

• | The commanded state of the ODM and the actual state of the control circuit do not match.

| OR

• | The ECM detects that the feedback voltage is not within a predicted range when the relay is commanded ON and OFF.

• | Either condition is present for more than 2 seconds.

### 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

• | This test procedure assumes that the vehicle battery has passed a load test and is completely charged. Refer to Battery Inspection/Test.

• | When disconnecting electrical connectors or removing fuses and relays from a fuse block, always inspect the component electrical terminals for corrosion and the mating electrical terminals for correct tension.

### Reference Information

#### Schematic Reference

• | Engine Controls Schematics

• | Power Distribution Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Probing Electrical Connectors

• | Electrical Center Identification Views

#### 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.

• | Relay Replacement

• | Control Module References for ECM replacement, setup, and programming