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 MalfunctionDTC 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
Important: A condition with the main relay will set multiple DTCs. The DTCs listed in the table will only set if a condition exists with the main relay.
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 main relay ON, ignition 1 voltage is supplied to the following fuses in the under bonnet electrical centre.
| • | The ECM or HFV6 ECM Fuse |
| • | The ETC Fuse |
| • | The PRE O2/CAM Fuse |
| • | The POST O2 Fuse |
| • | EVEN INJ/COIL Fuse |
| • | ODD INJ/COIL Fuse |
The ignition 1 voltage that is supplied to the ECM through the ECM fuse, provides power to the internal ECM circuits associated with the throttle actuator control (TAC) operation.
Conditions for Running the DTC
DTC P0685 and DTC P0686
| • | The battery voltage is between 10.5-18 volts. |
| • | The ignition is OFF. |
| • | The main relay has been commanded OFF. |
| • | The DTCs run continuously once the above condition is met. |
DTC P0687 P0689, and P0690
| • | The battery voltage is between 10.5-18 volts |
| • | The ignition is ON. |
| • | The main relay has been commanded ON. |
| • | The DTCs runs continuously once the above condition is 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 main relay feedback voltage is not within a predicted range when the main relay is commanded ON or 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 B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0685, P0686, P0687, P0689 and P0690 are type B 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 . |
| • | 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
Connector End View Reference
Electrical Information Reference
DTC Type Reference
Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Circuit/System Verification
- Using a scan tool, clear all DTCsl.
- Ignition OFF for 30 seconds.
- Ignition ON, observe the DTC information with a scan tool.
- View the DTC information with a scan tool. DTCs P0685, P0686, P0687, P0689 or P0690 should not set.
Circuit/System Testing
- Ignition OFF, disconnect the EC ignition or main relay.
- Connect a test lamp between the B+ supply circuit of the main relay and a known ground.
- Ignition ON, test for less than 0.1 volts difference between the actual battery voltage and the B+ supply voltage of the main relay.
- Ignition ON, connect a test lamp between the control circuit supply voltage and a known ground.
- Ignition OFF, connect a test lamp between the control circuit of the main relay and the earth circuit of the relay coil at underhood electrical centre.
- Ignition ON. The test lamp should illuminate when the ignition switch is cycled ON and OFF.
- If all circuits/connections test normal, test or replace the main relay.
Important: The test lamp is used to load the circuit and may not illuminate.
| ⇒ | If greater than 0.1 volts, test the B+ voltage circuit of the main relay for a short to ground or an open/high resistance. |
| ⇒ | If test lamp does not illuminate, test the control circuit for an open/high resistance or short to ground. If all circuits test normal replace the ECM. |
| ⇒ | If the test lamp does not illuminate, test the earth circuit of the relay coil for open/high resistance. |
Component Testing
- Measure for 70-110 ohms of resistance between terminals 85 and 86 of the main relay.
- Measure for infinite resistance between the following terminals of the main relay:
- Connect a 20-A fusible link 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 is not within the specified range, replace the main relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If continuity is detected, replace the main relay. |
| ⇒ | If the resistance measures more than 2 ohms, replace the main relay. |
Repair Instructions
Perform the Diagnostic Repair Verification .
| • | Engine Control Module Replacement for engine control module replacement, setup and programming. |
