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B3949




DTC B3948 or B3949

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 Descriptors

DTC B3948 01
- Left Front Turn Signal Circuit Short to Battery

DTC B3948 02
- Left Front Turn Signal Circuit Short to Ground

DTC B3948 04
- Left Front Turn Signal Circuit Open

DTC B3949 01
- Right Front Turn Signal Circuit Short to Battery

DTC B3949 02
- Right Front Turn Signal Circuit Short to Ground

DTC B3949 04
- Right Front Turn Signal Circuit Open

Diagnostic Fault Information






Circuit/System Description

Ground is applied at all times to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START positions. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM responds to the turn signal switch input by applying a pulsating voltage to the front and rear turn signal lamps through there respective control circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed ON and OFF.

Conditions for Running the DTC

Battery voltage must be between 9-16 V.

Conditions for Setting the DTC

DTC B3948 01 and B3948 04

* The BCM detects a short to ground or an open/high resistance in the F8DA fuse B+ circuit.

* The BCM detects an open/high resistance in the left front turn signal control circuit.

* The BCM detects an open/high resistance in the left front turn signal ground circuit.

DTC B3948 02

The BCM detects a short to ground in the left front turn signal control circuit.

DTC B3949 01 and B3949 04

* The BCM detects a short to ground or an open/high resistance in the F9DA fuse B+ circuit.

* The BCM detects an open/high resistance in the right front turn signal control circuit.

* The BCM detects an open/high resistance in the right front turn signal ground circuit.

DTC B3949 02

The BCM detects a short to ground in the right front turn signal control circuit.

Actions Taken When the DTC Sets

DTC B3948

* The left front turn signal is inoperative.

* The left turn signal indicator on the IPC flashes rapidly.

DTC B3949

* The right front turn signal is inoperative.

* The right turn signal indicator on the IPC flashes rapidly.

Conditions for Clearing the DTC

* The condition responsible for setting the DTC no longer exists.

* A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

Reference Information

Schematic Reference

* Exterior Lights Schematics Exterior Lights Schematics

* Body Control System Schematics [1][2]Body Control Systems

Exterior Lights Schematics Exterior Lights Schematics

Connector End View Reference

Component Connector End Views Outside Rearview Mirror - Driver

Description and Operation

Exterior Lighting Systems Description and Operation Exterior Lighting Systems

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 Control Module References for scan tool information

Circuit/System Testing

DTC B3948

1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module, ignition ON.

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

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, disconnect the X1 harness connector at the X51A fuse block - instrument panel.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, disconnect the X1 harness connector at the X51A fuse block - instrument panel.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K9 body control module.

• If the test lamp illuminates

3. Ignition OFF, connect the X1 harness connector at the K9 body control module.

4. Ignition OFF, exterior lamps OFF, disconnect the X110 harness connector at the E13LA headlamp assembly - left.

5. Test for less than 5 ohms between the ground circuit terminal A and ground.

• If 5 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 5 ohms

6. Connect a test lamp between the control circuit terminal E and ground, ignition ON.

7. Verify the test lamp turns ON and OFF when commanding the Left Front Turn Signal Lamp ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the X5 harness connector at the K9 body control module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K9 body control module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the X5 harness connector at the K9 body control module, ignition ON.

2. Test for less than 1 V between the control circuit terminal and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K9 body control module.

• If the test lamp turns ON and OFF

8. Test or replace the replace the E4N turn signal lamp - left.

DTC B3949

1. Ignition OFF, disconnect the X1 harness connector at the K9 body control module, ignition ON.

2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF, disconnect the X1 harness connector at the X51A fuse block - instrument panel.

2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.

• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF, disconnect the X1 harness connector at the X51A fuse block - instrument panel.

2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance, replace the K9 body control module.

• If the test lamp illuminates

3. Ignition OFF, connect the X1 harness connector at the K9 body control module.

4. Ignition OFF, exterior lamps OFF, disconnect the X120 harness connector at the E13RA headlamp assembly - right.

5. Test for less than 5 ohms between the ground circuit terminal A and ground.

• If 5 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 5 ohms

6. Connect a test lamp between the control circuit terminal E and ground, ignition ON.

7. Verify the test lamp turns ON and OFF when commanding the Right Front Turn Signal Lamp ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the X4 harness connector at the K9 body control module.

2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.

• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, replace the K9 body control module.

• If the test lamp is always ON

1. Ignition OFF, disconnect the X4 harness connector at the K9 body control module, ignition ON.

2. Test for less than 1 V between the control circuit terminal and ground.

• If 1 V or greater, repair the short to voltage on the circuit.

• If less than 1 V, replace the K9 body control module.

• If the test lamp turns ON and OFF

8. Test or replace the replace the E4P turn signal lamp - right.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the repair.

* Front Position Lamp Bulb Replacement Front Position Lamp Bulb Replacement

* Front Side Turn Signal Lamp Replacement Service and Repair

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

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