GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Yukon XL - 4WD 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC B3147 or B3148

Circuit Description

The Body Control Module (BCM) monitors and supplies an output voltage on the door unlock control circuit. When the BCM receives an unlock command from the remote control door lock receiver or the ignition key is removed after an automatic door lock function has been activated (if programmed), the BCM supplies voltage on the door unlock control circuit to unlock the passenger door(s).

Conditions for Running the DTC

B3147

    • The system voltage must be between 9.0 and 16.0 volts.
    • The BCM supplies a voltage signal on the door unlock control circuit.

B3148

The system voltage must be between 9.0 and 16.0 volts.

Conditions for Setting the DTC

B3147

    • When the BCM supplies a voltage signal on the door unlock control circuit and the door unlock control circuit is shorted to ground.
    • The above conditions must be met for 250 milliseconds.

B3148

    • When the door unlock control circuit is shorted to battery voltage.
    • The above conditions must be met for 180 seconds.

Action Taken When the DTC Sets
    • The door lock system will not UNLOCK the passenger door(s) from the keyless entry transmitter.
    • The door lock switches will not UNLOCK the doors.
    • The automatic door locks will not operate.

Conditions for Clearing the DTC

A DTC will clear after 100 consecutive ignition cycles without a fault present.

Diagnostic Aids
    • Perform a visual check for loose or poor connections at all related components
    • A short to battery voltage in the door unlock control circuit could be cause by a faulty door lock switch.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Listen for an audible click when the Door Unlock Relay operates. Command both the ON and OFF states. Repeat the commands as necessary.

    2.

  2. Verifies that the Body Control Module (BCM) is providing voltage to the door unlock relay.

    3.

  3. Tests for an open in the ground circuit to the door unlock relay.

    4.

  4. Tests if voltage is constantly being applied to the door unlock relay.

    5.

  5. After replacement of the BCM you must calibrate the new module for proper operation.

Step

Action

Yes

No

Schematic Reference: Door Lock/Indicator Schematics

1

Did you perform the Power Door Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Door Systems

2

  1. Install a scan tool.
  2. With a scan tool, command the door unlock relay ON and OFF.

Does the door unlock 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. Remove the door unlock relay.
  2. Probe the door unlock control circuit of the door unlock relay with a test lamp that is connected to a good ground.
  3. With a scan tool, command the door unlock 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 unlock control circuit and the ground circuit of the door unlock relay .
  2. With a scan tool, command the door unlock 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 unlock control circuit of the door unlock relay for a short to ground. 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 unlock control circuit of the door unlock 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 unlock 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 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 ground circuit of the door unlock relay . Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 13

--

11

Replace the door unlock relay .

Did you complete the replacement?

Go to Step 13

--

12

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

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