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. DTC P0686 indicates an open, high resistance, or a short to ground in the ignition 1 relay coil control circuit. If the fault detection circuit measures a low voltage condition, DTC P0686 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0686 Engine Controls Ignition Relay Control Circuit Low Voltage

Conditions for Running the DTC

    • The battery voltage is between 9-16 volts.
    • The ignition switch is turned ON.
    • DTC P0686 runs continuously once the above conditions are met.

Conditions for Setting the DTC

    • The ECM detects a lower 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 DTC diagnostic table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.
    • 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 1 relay armature

Test Description

  1. The engine will crank and run, with a short to ground on the ignition 1 relay coil control circuit. This condition could result in a discharged battery.

  2. The engine will crank but will not run, with a high resistance or an open 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 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

  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

Attempt to start the engine.

Does the engine start and run?

--

Go to Step 6

Go to Step 4

4

  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 in Wiring Systems.
  3. Notice: Refer to Test Probe Notice in the Preface section.

  4. Probe the battery positive voltage terminal for the ignition 1 relay coil at the underhood fuse block with a test lamp that is connected to a good ground. Refer to Troubleshooting with a Test Lamp in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 10

5

  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 battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 17

6

  1. Turn OFF the ignition.
  2. Remove the ignition 1 relay from the underhood fuse block with the J 43244 . Refer to Relay Replacement in Wiring Systems.
  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 battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 11

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 terminal at the underhood fuse block with a test lamp that is connected to battery positive voltage.

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 in Engine Electrical.
  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 in Wiring Systems.
  4. Connect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  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 battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 14

Go to Step 19

9

  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable at the battery. Refer to Battery Negative Cable Disconnection and Connection in Engine Electrical.
  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 in Wiring Systems.
  4. Disconnect the ECM electrical connector that contains the ignition 1 relay coil control circuit. Refer to Engine Control Module Replacement .
  5. Measure the resistance of the ignition 1 relay coil control circuit from the underhood fuse block electrical connector to the ECM electrical connector with a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.

Does the resistance measure greater than the specified value?

5 ohms

Go to Step 17

Go to Step 11

10

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 19

Go to Step 15

11

Measure the resistance from terminal #85 of the ignition 1 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 12

Go to Step 18

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 in Wiring Systems.

Did you find a condition?

--

Go to Step 19

Go to Step 13

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 21

Go to Step 20

14

Repair the short to ground in the ignition 1 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 21

--

15

Test for an intermittent and for a poor connection in the battery positive cable between the underhood fuse block and the battery.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 16

16

Replace the battery positive cable to the underhood fuse block. Refer to Battery Positive Cable Replacement in Engine Electrical.

Did you complete the replacement?

--

Go to Step 21

--

17

Repair the high resistance or an open in the ignition 1 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 21

--

18

Replace the ignition 1 relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

--

Go to Step 20

--

19

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 21

--

20

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 21

--

21

  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 22

22

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