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

Important: A condition with the main relay will set multiple DTCs. Only when there is a condition with the main relay, the DTC list in the table will set.

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 the ground path 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 underhood fuse block:

• | The engine control module or the HFV6 engine control module fuse

• | The transmission output speed fuse - only CTS

• | Fuses

• | POST O2 Fuse

• | Even Injector/Coil Fuse

• | Odd Injector/Coil Fuse

The ignition 1 voltage is supplied to the ECM through the ECM fuse, it provides power to the internal ECM circuits and the throttle actuator control (TAC) operation.

### Conditions for Running the DTC

#### P0685, P0686 and P0687

• | The engine speed is more than 80 RPM.

• | Battery voltage is between 10-18 volts.

• | The ECM has commanded the ignition relay ON and OFF at least once during the ignition cycle.

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

### Conditions for Setting the DTC

#### P0689 and P0690

• | The ECM detects that the power is not turned OFF.

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

• | There is an open, a short to ground or a short to voltage on the engine control system ignition relay control circuit.

| OR

• | The ECM detects that the main relay feedback voltage is less than 6 volts, when the main relay is commanded ON or OFF.

• | Every condition exists for more than 50 seconds.

### Action Taken When the DTC Sets

• | Do not illuminate MIL.

• | The ECM records the operating conditions at the time when the diagnostic test fails. The ECM displays the failure information in the Failure Records on the scan tool.

### Conditions for Clearing the MIL/DTC

• | The DTC becomes history when the conditions for setting the DTC are no longer present.

• | The history DTC is cleared after 40 malfunction free warm-up cycles.

• | The ECM receives the clear code command from the scan tool.

### 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 correct tension.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Front of Vehicle/Engine Compartment Component Views.

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the underhood fuse block terminals, component wire harness terminals, or the ECM wire harness connector terminals.

Step | Action | Value | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Component Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Turn the ignition switch to ON position, use the scan tool to clear the DTCs.
2. Turn the ignition switch to OFF position for 30 seconds.
3. Turn the ignition switch to ON position, observe the DTC information with a scan tool.

Does the DTC fail this ignition?

--

Go to Step 3

Go to Diagnostics Aids

3 |

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

1. Turn the ignition switch to OFF position, disconnect the engine control system ignition or main relay.
2. Connect a test lamp to between the coil side B+ supply circuit of the main relay and the negative terminal of the battery.
3. Turn the ignition switch to ON position, detects the Voltage parameter between the B+ voltage circuit of the main relay and positive battery terminal

Is the voltage less than the specified value?

0.1 V

Go to Step 5

Go to Step 4

4 | Repair a short to ground, an open or high resistance of the B+ voltage circuit to the coil side of the main relay. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 16 | --
5 |

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

1. Connect a test lamp between the B+ voltage supply circuit to the switch side of the main relay and the negative battery terminal.
2. Turn the ignition switch to ON position, detects the Voltage parameter between the B+ voltage circuit of the main relay and positive battery terminal.

Is the voltage less than the specified value?

0.1 V

Go to Step 7

Go to Step 6

6 | Repair a short to ground, an open or high resistance of the B+ voltage circuit to the switch side of the main relay. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 16 | --
7 |

1. Turn the ignition switch to OFF position, connect a test lamp between the control circuit of the main relay and the B+ voltage supply circuit to the coil side of the main relay.
2. Turn the ignition switch to ON position. The test lamp should turn ON when the ignition switch is turned ON, and the test lamp should turn OFF when the ignition switch is turned OFF.

Is the voltage within the specified range for both circuits?

--

Go to Step 12

Go to Step 8

8 | Does the test lamp always remain illuminated? | -- | Go to Step 9 | Go to Step 10
9 | Check the control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14
10 | Does the test lamp always remain OFF? | -- | Go to Step 11 | --
11 | Test the control circuit for a short to voltage, an open or high resistance. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14
12 |

Note: The ignition 1 voltage circuit is between the main relay and engine control module. The ignition 1 voltage circuit is a feedback circuit.

1. Connect a 3-amp fused jumper wire between the B+ supply voltage circuit and the ignition 1 voltage circuit of the main relay.
2. Attempt to start the engine. The engine should start.

Does the engine start?

--

Go to Step 15

Go to Step 13

13 | Test the ignition 1 voltage circuit between the main relay and the ECM for a short to ground, an open or high resistance. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 16 | Go to Step 14
14 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 16 | --
15 | Replace the main relay. Refer to Relay Replacement. Did you complete the replacement? | -- | Go to Step 16 | --
16 |

1. Clear any DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate he vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 2

Go to Step 17

17 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK