B3809

DTC B3809

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B3809
- Rear Door Unlock Relay Circuit

Diagnostic Fault Information






Circuit/System Description

The body control module (BCM) internally grounds the door unlock relay control circuit for the rear door unlock relay when it receives a class 2 message from the driver door module (DDM), passenger door module (PDM) or the liftgate module (LGM) with a keyless entry transmission. When the BCM grounds the door unlock relay control circuit the rear door unlock relay is energized and unlocks the rear doors.

Conditions for Running the DTC

The battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

The door unlock relay control circuit is shorted to ground or open for more than 1 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 rear 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 rear doors will lock but not unlock.

Conditions for Clearing the DTC

* This DTC will clear on current status after the condition for setting the fault is corrected.
* A history DTC will clear after 50 consecutive ignition cycles without a fault present.

Circuit/System Verification

Command the rear doors to Lock and Unlock with a scan tool. The rear doors should lock and unlock.

Circuit/System Testing

1. Ignition OFF, disconnect the UNLOCK relay.
2. Verify that a test lamp illuminates between the B+, ignition circuit terminal 87 and ground.

^ If the test lamp does not illuminate and the B+ circuit fuse is open, test the control circuit terminal 30 for a short to ground. If the circuit tests normal, test or replace the rear fuse block.

3. Verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.

^ If the test lamp does not illuminate, test or replace the rear fuse block.

4. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
5. Command the rear doors to Lock and Unlock with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

^ If the test lamp is always ON, test the relay control circuit for a short to ground. If the circuit tests normal, replace the BCM.

^ If the test lamp is always OFF, test the relay control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

6. If all circuits test normal, test or replace the UNLOCK relay.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Relay Replacement (Attached to Wire Harness) Relay Replacement (Within an Electrical Center)
* Rear Electrical Center or Junction Block Replacement