Circuit Description
The powertrain 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 (ODM). One ODM output control is configured to operate as a low side driver for the main relay. The low side driver for the main relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the ODM low side driver to turn ON, the expected voltage on the relay coil control circuit should be a low voltage condition. DTC P0687 indicates a short to battery positive voltage, or ignition 1 voltage, on the main relay coil control circuit. If the fault detection circuit measures a high voltage condition, DTC P0687 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0687 Engine Controls Ignition Relay Control Circuit High Voltage
Conditions for Running the DTC
| • | The battery voltage is between 9-16 volts. |
| • | The ignition switch is turned ON. |
| • | DTC P0687 runs continuously when the above conditions are met. |
Conditions for Setting the DTC
| • | The ECM detects a higher than expected voltage on the relay coil control circuit. |
| • | The above condition is present 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 powertrain 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. |
Test Description
The number below refers to the step number on the diagnostic table.
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 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Intermittent Conditions | |
3 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 4 |
4 |
Does the test lamp illuminate? | -- | Go to Step 5 | Go to Step 9 |
5 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 13 |
6 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 17 |
7 |
Notice: Refer to Test Probe Notice in the Preface section. Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 13 |
8 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 17 |
9 | Measure the resistance from terminal #30 of the powertrain relay to terminal #87 with a DMM. Does the DMM display the specified value? | ∞ ohms | Go to Step 10 | Go to Step 15 |
10 | Measure the resistance from terminal #30 of the powertrain relay to terminal #86 with a DMM. Does the DMM display the specified value? | ∞ ohms | Go to Step 11 | Go to Step 15 |
11 | Measure the resistance from terminal #85 of the powertrain relay to terminal #87 with a DMM. Does the DMM display the specified value? | ∞ ohms | Go to Step 12 | Go to Step 15 |
12 | Test for an intermittent and for a poor connection at the powertrain relay location of the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find a condition? | -- | Go to Step 17 | Go to Intermittent Conditions |
13 | Test for shorted terminals and poor connections 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 18 | Go to Step 16 |
14 | Repair the short to voltage in the powertrain relay coil control 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 18 | -- |
15 | Replace the powertrain relay. Refer to Relay Replacement in Wiring Systems. Did you complete the replacement? | -- | Go to Step 18 | -- |
16 | 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 18 | -- |
17 | 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 18 | -- |
18 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Step 19 |
19 | 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 |
