B3809
DTC B3809
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (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 lock relay control circuit for the rear door lock relay when it receives a serial data message from the driver door switch (DDS) or passenger door switch (PDS). When the BCM grounds the door lock relay control circuit the rear door lock relay is energized and locks the rear doors.
Conditions for Running the DTC
The battery voltage must be between 9-16 volts.
Conditions for Setting the DTC
The BCM detects a short to ground on the door unlock relay control circuit for greater than 60 seconds
Action Taken When the DTC Sets
The rear doors will not unlock when using the door lock switch.
Conditions for Clearing the DTC
* The DTC will be current for as long as the fault is present.
* When the fault is no longer present, the DTC will be a history DTC
* A history DTC will clear after 50 ignition cycles
Reference Information
Schematic Reference
Door Lock/Indicator Schematics (Door Lock/Indicator Schematics)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Power Door Locks Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
Ignition ON, command the rear doors to LOCK and UNLOCK with a scan tool. The rear doors should LOCK and UNLOCK when changing between the commanded states.
Circuit/System Testing
1. Ignition OFF, disconnect the UNLOCK relay.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 86 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Connect a test lamp between the B+ circuit terminal 86 and the control circuit terminal 85.
4. Command the rear doors to LOCK and UNLOCK with a scan tool. The test lamp should briefly illuminate when changing between the commanded states.
• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the BCM.
• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.
5. If all circuits test normal, test or replace the UNLOCK relay.
Component Testing
Relay Test
1. Ignition OFF, disconnect the UNLOCK relay.
2. Test for 60-200 ohms between terminals 85 and 86.
• If not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
* 30 and 86
* 30 and 87
* 30 and 85
* 85 and 87
• If less than the specified value, replace the relay.
4. Test for less than 2 ohms between terminals 30 and 87A.
• If greater than the specified range, replace the relay.
5. Install a 3-amp fused jumper wire between the relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.
• If greater than specified range, replace the relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (Relay Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (Relay Replacement (Within an Electrical Center))
* Control Module References (Programming and Relearning) for BCM replacement, programming, and setup