GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The ignition 1 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 ignition 1 relay. The low side driver for the ignition 1 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 ignition 1 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 once 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 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 ignition 1 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 .
    • The following underhood fuse block terminal locations correspond to the ignition 1 relay circuits:
       - F13--Ignition 1 voltage circuit.
       - F14--Ignition 1 relay coil control circuit.
       - H13--Battery positive voltage circuit to the ignition 1 relay coil.
       - H14--Battery positive voltage circuit to the ignition relay armature.

Test Description

  1. The engine will crank but will not run with a short to battery positive voltage, or a short to the ignition 1 voltage on the ignition 1 relay coil control circuit.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Turn ON the ignition, with the engine OFF.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze/Frame Failure Records.

Did the DTC fail this ignition?

--

Go to Step 3

Go to Intermittent Conditions

3

  1. Turn OFF the ignition.
  2. Remove the ignition 1 relay from the underhood fuse block with the J 43244 Relay Puller Pliers. Refer to Relay Replacement .
  3. Notice: Refer to Test Probe Notice in the Preface section.

  4. Probe the ignition 1 relay coil control circuit terminal at the underhood fuse block, with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp .

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 4

4

  1. Turn ON the ignition, with the engine OFF.
  2. Probe the ignition 1 relay coil control circuit terminal at the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 9

5

  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) electrical connector that contains the ignition 1 relay coil control circuit. Refer to Engine Control Module Replacement . Turn ON the ignition, with the engine OFF.
  3. Turn ON the ignition, with the engine OFF.
  4. Notice: Refer to Test Probe Notice in the Preface section.

  5. Probe the ignition 1 relay coil control circuit at the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 13

6

  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the ignition 1 relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Disconnect the ignition 1 relay coil control circuit terminal from the underhood fuse block electrical connector.
  5. Connect the electrical connector that contained the ignition 1 relay coil control circuit to the underhood fuse block.
  6. Connect the negative battery cable at the battery.
  7. Turn ON the ignition, with the engine OFF.
  8. Probe the ignition 1 relay coil control circuit terminal at the electrical connector for the underhood fuse block with a test lamp that is connected to good ground.

Does the test lamp illuminate?

--

Go to Step 14

Go to Step 17

7

  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) electrical connector that contains the ignition 1 relay coil control circuit. Refer to Engine Control Module Replacement .
  3. Notice: Refer to Test Probe Notice in the Preface section.

  4. Probe the ignition 1 relay coil control circuit at the underhood fuse block with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 13

8

  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection .
  3. Disconnect the underhood fuse block electrical connector that contains the ignition 1 relay coil control circuit. Refer to Underhood Electrical Center or Junction Block Replacement .
  4. Connect the negative battery cable at the battery.
  5. Probe the ignition 1 relay coil control circuit terminal at the underhood fuse block electrical connector with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 14

Go to Step 17

9

Measure the resistance from terminal #30 of the ignition 1 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 ignition 1 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 ignition 1 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 ignition 1 relay location of the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections .

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 .

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

14

Repair the short to voltage in the ignition 1 relay coil control circuit between the underhood fuse block electrical connector and the ECM electrical connector. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 18

--

15

Replace the ignition 1 relay. Refer to Relay Replacement .

Did you complete the replacement?

--

Go to Step 18

--

16

Replace the ECM. Refer to Control Module References 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 .

Did you complete the replacement?

--

Go to Step 18

--

18

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

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

System OK