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 Descriptor

DTC P0685: Engine Control Ignition Relay Circuit Malfunction
DTC P0686: Engine Control Ignition Relay Circuit Low Voltage
DTC P0687: Engine Control Ignition Relay Circuit High Voltage
DTC P0689: Engine Control Ignition Relay Feedback Circuit Low Voltage
DTC P0690: Engine Control Ignition Relay Feedback Circuit High Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
B+ Supply Voltage - Coil | P0685 | P0685 | P0685 | -- | --
B+ Supply Voltage - Switch | -- | P0689 | P0689 | P0690 | --
Relay Control Circuit | P0686 | P0685 | P0685 | P0687 | P0685
Ignition 1 Voltage Circuit | -- | P0689 | P0689 | P0690 | --

### Circuit/System Description

The engine controls (EC) ignition relay or main 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 switch contact at all times. The engine control module (ECM) supplies voltage to the relay coil control circuit via an internal integrated circuit called an output driver. When the ECM commands the powertrain relay ON, ignition voltage is supplied to several fuses in the underhood fuse block.

The fuse that provides power to terminal 3, 5, or 6 of ECM connector X2 feeds the internal ECM circuits associated with the throttle actuator control (TAC) operation.

### Conditions for Running the DTC

#### DTC P0685, P0686, and P0687

• | The battery voltage is between 10-18 volts.

• | The engine speed is greater than 80 RPM.

• | The powertrain relay has been commanded ON and OFF.

• | The DTCs run continuously once the above condition is met.

#### DTC P0689 and P0690

• | The battery voltage is between 10-18 volts.

• | The ignition is ON.

• | The DTCs runs continuously once the above condition is met.

### Conditions for Setting the DTC

#### P0685, P0686, and P0687

The commanded state of the driver and the actual state of the control circuit do not match for greater than 4 seconds or for a cumulative of 30 seconds.

#### P0689 and P0690

The ECM detects that powertrain relay feedback voltage is less than 6 volts for greater than 1 second, when the powertrain relay is commanded ON or OFF. The condition exists for 4 seconds, or for a cumulative of 30 seconds.

### Action Taken When the DTC Sets

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

### Conditions for Clearing the MIL/DTC

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

### Diagnostic Aids

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

• | An open in the relay control circuit will cause no communication with the ECM when the ignition switch is cycled OFF and then ON after the initial failure. The malfunction indicator lamp (MIL) will flash rapidly and other relays can be heard turning on and off with the ignition ON.

• | 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 tightness.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Air Intake System Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### 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 ON, you should be able to communicate with the ECM using a scan tool.
2. Ignition ON, view the DTC information with a scan tool. DTC P0685, P0686, P0687, P0689, or P0690 should not set.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the powertrain relay.

Note: The test lamp is used to load the circuit and may not illuminate.

2. Connect a test lamp between the B+ supply circuit to the coil side of the powertrain relay and the negative terminal of the battery.
3. Ignition ON, test for less than 0.1 V between the B+ voltage circuit of the powertrain relay and the positive battery terminal.

⇒ | If greater than the specified value, repair the B+ voltage circuit to the coil side of the powertrain relay for a short to ground or an open/high resistance.

Note: The test lamp is used to load the circuit and may not illuminate.

4. Connect a test lamp between the B+ voltage supply circuit to the switch side of the powertrain relay and the negative terminal of the battery.
5. Ignition ON, test for less than 0.1 V between the B+ voltage circuit of the powertrain relay and the positive battery terminal.

⇒ | If greater than the specified value, repair the B+ voltage circuit to the switch side of the powertrain relay for a short to ground or an open/high resistance.

6. Ignition OFF, connect a test lamp between the control circuit of the powertrain relay and the B+ voltage supply circuit to the coil side of the powertrain relay.
7. Ignition ON. the test lamp should turn ON when the ignition switch is cycled ON and OFF when the ignition switch is cycled OFF.

⇒ | If the test lamp remains ON all the time, test for a short to ground on the control circuit. If the circuit/connections test normal, replace the ECM.

⇒ | If the test lamp remains OFF all the time, test for a short to voltage or an open/high resistance on the control circuit. If circuit/connections test normal, replace the ECM.

8. Connect a 15 A fused jumper wire between the B+ supply voltage circuit and the ignition voltage circuit of the powertrain relay.
9. Attempt to start the engine. The engine should start.

⇒ | If the engine does not start, test the ignition voltage circuit between the powertrain relay and the ECM for a short to ground or for an open/high resistance. If the circuit/connections test normal, replace the ECM.

10. If all circuits/connections test normal, test or replace the powertrain relay.

### Component Testing

1. Measure for 200-250 Ω 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 the following terminals of the main relay:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If continuity is detected, replace the main relay.

3. Connect a 20 A fused 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 Ω between terminals 30 and 87 of the relay.

⇒ | If the resistance measures greater than 2 Ω, replace the main relay.

### Repair Instructions

Perform the Diagnostic Repair Verification.

• | Relay Replacement.

• | Engine Control Module Replacement for engine control module replacement, setup, and programming