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DTC B3938

DTC B3938

Diagnostic Instructions


• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• Diagnostic Procedure Instructions provides an overview of each diagnostic category.


DTC Descriptors

DTC B3938 01

Fuel Door Actuator Lock Circuit Short to Battery

DTC B3938 02

Fuel Door Actuator Lock Circuit Short to Ground

DTC B3938 04

Fuel Door Actuator Lock Circuit Open

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Fuel Door Lock Relay Control B3938 02 B3938 04 B3938 01 -
Rear Fuse Block Ground - B3938 04 - -


Circuit/System Description

The locking and unlocking of the fuel door is a function of the power door lock system. The fuel door unlatch actuator shares the circuit with the door latch unlock control circuit. The body control module (BCM), upon receipt of a lock switch lock or unlock signal, will switch the appropriate door latch, as well as a fuel filler door unlatch actuator control circuits to B+ voltage. The opposing side of the door latch and fuel filler door unlatch actuator is connected to ground provided by the BCM through the other the door latch control circuits, along with the fuel filler door unlatch actuator, will lock or unlock as commanded.

Conditions for Running the DTC

When the relay is actively commanded by the BCM.

Conditions for Setting the DTC

B3938 01

The BCM detects a short to voltage in the FUEL DOOR relay control circuit.

B3938 02

The BCM detects a short to ground in the FUEL DOOR relay control circuit.

B3938 04

The BCM detects an open/high resistance in the FUEL DOOR relay control circuit.

Action Taken When the DTC Sets

The fuel door latch will malfunction and the fuel filler door may not be able to be opened.

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

Release Systems Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel Fill Door Description and Operation

Electrical Information Reference


• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, command the doors to LOCK and UNLOCK by using the central door lock switch, the M27 fuel door release actuator should LOCK and UNLOCK when changing between the commanded states.

Circuit/System Testing


1. Ignition OFF, disconnect the X2 harness connector at the X53 fuse block-rear.

2. Connect a test lamp between the control circuit terminal 31 and ground

3. Command the doors to LOCK with a scan tool. The test lamp should briefly illuminate during the LOCK command.

4. If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.

5. If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K9 BCM.

6. If all circuits test normal, test or replace the X53 fuse block-rear.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Front Compartment Fuse Block Replacement

• Control Module References for BCM replacement, setup, and programming