Circuit Description
The main relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature 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 module. When the ECM commands the relay ON, ignition 1 voltage is supplied to the ECM through the V8 ECM fuse in the underhood fuse block. This ignition 1 voltage input to the ECM provides the ignition power for the ECM circuitry and is also used to confirm the relay contacts have closed. A voltage less than 10 volts indicates an open, high resistance, or a short to ground in the ignition 1 voltage circuit to the ECM. This DTC will set when the ECM detects less than 10 volts on the ignition 1 voltage circuit to the ECM, after the ignition switch is turned ON.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0689 Engine Controls Ignition Relay Feedback Circuit Low Voltage
Conditions for Running the DTC
| • | The battery voltage is more than 11 volts for 1.5 seconds with the ignition ON. |
| • | DTC 0689 runs continuously once the above condition is met. |
Conditions for Setting the DTC
The ECM detects less than 10 volts on the ignition 1 voltage circuit for more than 200 milliseconds.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
| • | The main relay will remain powered up for 15 seconds after the ignition switch is turned OFF. |
| • | This diagnostic table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical. |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views and Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 | If DTCs P0686 or DTC P0687 are set along with DTC P0689, then DTC P0686 or DTC P0687 must be diagnosed first. Is DTC P0686 or DTC P0687 also set? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | Go to Step 3 |
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Intermittent Conditions |
4 |
Does the test lamp illuminate on both test points of the V8 ECM fuse? | -- | Go to Step 8 | Go to Step 5 |
5 | Does the test lamp illuminate on one test point of the V8 ECM fuse? | -- | Go to Step 6 | Go to Step 10 |
6 |
Does the test lamp illuminate? | -- | Go to Step 20 | Go to Step 7 |
7 | Test the underhood fuse block bus bar circuit from the V8 ECM fuse to the underhood fuse block electrical connector for a short to ground. Refer to Circuit Testing in Wiring Systems. Did you find a condition? | -- | Go to Step 22 | Go to Step 19 |
8 |
Does the resistance measure the more than the specified value? | 3 ohms | Go to Step 21 | Go to Step 9 |
9 | Test the underhood fuse block ignition 1 voltage bus bar circuit from the V8 ECM fuse to the underhood fuse block electrical connector for a high resistance or an open. Refer to Circuit Testing in Wiring Systems. Did you find a condition? | -- | Go to Step 22 | Go to Step 19 |
10 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 12 |
11 | Test the underhood fuse block ignition 1 voltage bus bar circuit between the main relay and the V8 ECM fuse for a high resistance or an open. Refer to Circuit Testing in Wiring Systems. Did you find a condition? | -- | Go to Step 22 | Go to Step 13 |
12 | Probe the mounting stud for the battery positive cable at the underhood fuse block with a test lamp that is connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 22 | Go to Symptoms - Engine Electrical in Engine Electrical |
13 | Measure the resistance from terminal #85 of the main relay to terminal #86 with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems. Does the resistance measure within the specified range? | 70-110 ohms | Go to Step 14 | Go to Step 23 |
14 | Measure the resistance from terminal #30 of the main relay to terminal #87 with a DMM. Does the DMM display the specified value? | ∞ ohms | Go to Step 15 | Go to Step 23 |
15 | Measure the resistance from terminal #30 of the main relay to terminal #85 with a DMM. Does the DMM display the specified value? | ∞ ohms | Go to Step 16 | Go to Step 23 |
16 | Measure the resistance from terminal #85 of the main relay to terminal #87 with a DMM. Does the DMM display the specified value? | ∞ ohms | Go to Step 17 | Go to Step 23 |
17 |
Does the resistance measure greater than the specified value? | 3 ohms | Go to Step 23 | Go to Step 18 |
18 | Test for an intermittent and for a poor connection at the main relay location on the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find a condition? | -- | Go to Step 22 | Go to Intermittent Conditions |
19 | Test for shorted terminals and poor connection at the ECM electrical connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Micro .64 Connectors in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 24 |
20 | Repair the short to ground in the main voltage circuit between the underhood fuse block electrical connector and the ECM electrical connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 25 | -- |
21 | Repair the high resistance or an open in the ignition 1 voltage circuit between the underhood fuse block electrical connector and the ECM electrical connector. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 25 | -- |
22 | Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems. Did you complete the replacement? | -- | Go to Step 25 | -- |
23 | Replace the main relay. Refer to Relay Replacement in Wiring Systems. Did you complete the replacement? | -- | Go to Step 25 | -- |
24 | Replace the ECM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 25 | -- |
25 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Step 26 |
26 | 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 in Vehicle DTC Information | System OK |
