GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Express - AWD 🢒 Restraints 🢒 SIR 🢒 DTC B3809

Circuit Description

The body control module (BCM) internally grounds the door unlock relay control circuit for the door unlock relay when it receives a switched ground signal from any door lock switch or a keyless entry unlock transmission. When the BCM grounds the door unlock relay control circuit, the door unlock relay is energized and unlocks the doors.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B3809 Passenger Door Unlock relay Circuit

Conditions for Running the DTC
    • Battery voltage is between 9-16 volts.
    • The DTC will set if the door unlock function is active or inactive.

Conditions for Setting the DTC

The DTC will set if the passenger door unlock relay control circuit is shorted to ground or open for more than one second.

Action Taken When the DTC Sets
    • If a short to ground is present on the door unlock relay control circuit, the door unlock relay will be energized and the door lock actuators will be held in the unlock position and will not lock.
    • If an open condition is present on the door unlock relay control circuit, the doors will lock but not unlock.

Conditions for Clearing the DTC

When the fault is no longer present, the BCM changes the current DTC to a history DTC. The BCM will clear the history DTC after 50 fault-free ignition cycles.

Diagnostic Aids
    • DTC B3809 could also set if the PASS UNLK relay winding is open.
    • If both DTC B3808 and B3809 are set as current, the battery positive voltage circuit or the Door LKS fuse could be open. If the Door LKS fuse is open, the cause is most likely one of the following:
       - A short to ground in the relay battery positive voltage circuit
       - A short to ground in the door lock/latch actuator lock or unlock control circuits

Test Description

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

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

    2.

  2. This step tests for voltage at the coil side of the PASS UNLK relay. The Door LKS fuse supplies power to the coil side of the PASS UNLK relay.

    3.

  3. This step verifies that the BCM is providing ground to the PASS UNLK relay.

    4.

  4. This step tests if ground is constantly being applied to the PASS UNLK 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. With a scan tool, command the passenger door unlock relay ON and OFF.

Does the passenger 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 PASS UNLK relay.
  2. Probe the battery positive voltage circuit of the PASS UNLK relay with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 4

Go to Step 8

4

  1. Connect a test lamp between the PASS UNLK relay control circuit and the battery positive voltage circuit of the PASS UNLK relay.
  2. With a scan tool, command the rear door unlock relay ON and OFF .

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

Go to Step 9

Go to Step 5

5

Does the test lamp remain illuminated without being commanded?

Go to Step 7

Go to Step 6

6

Test the passenger door unlock relay control circuit for an open or a poor connection. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 10

7

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

Did you find and correct the condition?

Go to Step 14

Go to Step 10

8

Test for an open or short to ground in the battery positive voltage circuit of the PASS UNLK relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 14

Go to Step 11

9

Inspect for poor connections at the PASS UNLK 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 14

Go to Step 12

10

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 14

Go to Step 13

11

Repair the short to ground in the door lock/latch actuator lock or unlock control circuits. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 14

--

12

Replace the PASS UNLK relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 14

--

13

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 14

--

14
  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