GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The door lock control circuit from the body control module (BCM) controls the door lock relay. When the BCM receives a door lock signal, the BCM supplies battery positive voltage to the relay.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC B3137 All Door Lock Circuit Low
    • DTC B3138 All Door Lock Circuit High

Conditions for Running the DTC

The keyfob lock button is pressed or a door lock switch is pressed to the lock position for DTC B3137. The battery positive voltage supplied to the BCM is within normal operating range, 9-16 volts, for DTC B3138.

Conditions for Setting the DTC

The door lock control circuit is shorted to ground for 0.2 second, for DTC B3137. The door lock control circuit is shorted to battery positive voltage for 0.2 second, for DTC B3138.

Action Taken When the DTC Sets

The BCM disables the door lock output for the remainder of the ignition cycle.

Conditions for Clearing the DTC

    • A current DTC B3137 or DTC B3138 clears when the malfunction is no longer present and the ignition switch is cycled.
    • All BCM history codes clear after 100 ignition cycles with no current codes active during the 100 ignition cycles.

Diagnostic Aids

If the DTC is a history DTC, the problem may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Listen for an audible click when the door lock relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.

  2. This step verifies that the body control module is providing voltage to the door lock relay.

  3. This step tests for an open in the ground circuit to the door lock relay.

  4. This step tests if voltage is constantly being applied to the door lock relay.

Step

Action

Yes

No

Schematic Reference: Door Lock/Indicator Schematics

Connector End View Reference: Power Door Systems 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. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the door lock relay ON and OFF.

Does the door lock relay turn ON and OFF with each command?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the door lock relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the door lock control circuit of the door lock relay with a test lamp connected to a good ground.
  5. With a scan tool, command the door lock relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 4

Go to Step 5

4

  1. Connect a test lamp between the door lock control circuit of the door lock relay and the ground circuit of the door lock relay.
  2. With a scan tool, command the door lock relay ON and OFF.

Does the test lamp turn ON and OFF with each command?

Go to Step 8

Go to Step 10

5

Does the test lamp remain illuminated with each command?

Go to Step 7

Go to Step 6

6

Test the door lock control circuit of the door lock relay for a short to ground or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

7

Test the door lock control circuit of the door lock relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 9

8

Inspect for poor connections at the door lock relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

9

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

10

Repair the open in the ground circuit of the door lock relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the door lock relay.

Did you complete the replacement?

Go to Step 13

--

12

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 13

--

13

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

Go to Step 2

System OK