For 1990-2009 cars

### 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 Descriptor

DTC B3938 02: Fuel Door Actuator Lock Circuit Short to Ground

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Doors Lock Control | B3135 02, 1 | 1 | 1 | --
Fuel Door Relay Coil Control | B3938 02 | 1 | 1 | --
Fuel Door Relay Controlled Output | 1 | 1 | 1 | --
Relay Coil Ground | -- | 1 | 1 | --
1. Fuel Filler Door Release Inoperative

### Circuit/System Description

The locking and unlocking of the fuel door is a function of the power door lock system. The fuel door release actuator is supplied by the door lock signal circuit and the driver door unlock signal circuit which is switched through the fuel door relay. The fuel door relay coil is controlled by the body control module (BCM). When the vehicles doors are unlocked, the body control module (BCM) will respond by applying voltage to the fuel door relay coil control circuit. This energizes the coil causing the switch contacts to close. With the switch contacts closed, the driver door unlock circuit supplies B+ or ground to the fuel door release actuator , unlocking the fuel door.

### Conditions for Running the DTC

The system voltage is 9-18 V.

### Conditions for Setting the DTC

#### B3898 02

The BCM detects a short to ground on the fuel filler door relay control circuit.

### Action Taken When the DTC Sets

The remote fuel filler door will be inoperative.

### Conditions for Clearing the DTC

• | This 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

#### 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 Fuel Door Release ON and OFF with a scan tool. The fuel filler door should lock and unlock.

### Circuit/System Testing

1. Ignition OFF, disconnect the KR94 Fuel Door Release Actuator Relay.
2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 85 and ground.

⇒ | If the test lamp illuminates, test the control circuit for a short to voltage.

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

⇒ | If the test lamp does not illuminate, test the ground circuit for a short to voltage or an open/high resistance. If the circuit tests normal, test or replace the KR94 Fuel Door Release Actuator Relay.

4. Press the door unlock button on the door lock switch and verify that a test lamp illuminates between the door unlock control circuit terminal 30 and ground.

⇒ | If the test lamp does not illuminate, test the door unlock control circuit for an open/high resistance.

5. Disconnect the harness connector at the M27 Fuel Door Release Actuator.
6. Test for less than 2 Ω between the M27 Fuel Door Release Actuator door lock control circuit terminal 1 and ground.

⇒ | If greater than the specified range, test the door lock control circuit for an open/high resistance.

7. Connect the harness connector at the M27 Fuel Door Release Actuator.
8. Connect a 15 A fused jumper wire between the door unlock control circuit terminal 30 and the control circuit terminal 87. Verify the M27 Fuel Door Release Actuator is activated when the door unlock switch is pressed.

⇒ | If the M27 Fuel Door Release Actuator does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the M27 Fuel Door Release Actuator.

9. Connect a DMM, set on the diode setting, between the control circuit terminal 86 and ground.
10. Command the Fuel Door Release Unlatch with a scan tool. The DMM reading should be greater than 2.5 V or display O.L.

⇒ | If less than the specified value, test the control circuit for a short to voltage or short to ground. If the circuits test normal, replace the K9 Body Control Module (BCM).

11. Command the Fuel Door Release Latch with a scan tool. The DMM reading should be less than 1 V.

⇒ | If greater than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the K9 Body Control Module (BCM).

12. If all circuits test normal, test or replace the KR94 Fuel Door Release Actuator Relay.

### Component Testing

#### Relay Test

1. Ignition OFF, disconnect the KR94 Fuel Door Release Actuator Relay.
2. Test for 2 Ω between terminals 85 and 86.

⇒ | If the resistance is not within the specified range, replace the KR94 Fuel Door Release Actuator Relay.

3. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the KR94 Fuel Door Release Actuator Relay.

4. Test for less than 2 Ω between terminals 30 and 87A.

⇒ | If greater than the specified range, replace the KR94 Fuel Door Release Actuator Relay.

5. Install a 15 A fused jumper wire between relay terminal 85 and 12 V. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.

⇒ | If greater than the specified range, replace the KR94 Fuel Door Release Actuator Relay.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Fuel Tank Filler Door Lock Actuator Replacement

• | Relay Replacement

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