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B3948




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 vehicle ON/OFF switch in the SERVICE MODE or ON 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 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 F8DR (TRN SIG/LCKS) 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 F6DR (APO/EXT LIGHTS) 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 instrument cluster flashes rapidly.

DTC B3949

* The right front turn signal is inoperative.

* The right turn signal indicator on the instrument cluster 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 vehicle ON/OFF switch cycles have occurred.

Reference Information

Schematic Reference

* Exterior Lights Schematics Exterior Lights Schematics

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

Connector End View Reference

Component Connector End Views Hybrid/EV Battery Pack X1

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 Programming and Relearning for scan tool information

Circuit/System Testing

DTC B3948

1. Vehicle OFF, disconnect the X5 harness connector at the K9 body control module, vehicle in Service Mode.

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. Vehicle OFF.

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. Vehicle OFF.

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. Vehicle OFF, connect the X5 harness connector at the K9 body control module.

4. Vehicle OFF, exterior lamps OFF, disconnect the harness connectors at the components listed below.

* E4N turn signal lamp - left

* E4Y turn signal repeater lamp - left

5. Test for less than 10 ohms between the ground circuit terminals listed below and ground.

* E4N turn signal lamp - left terminal 1

* E4Y turn signal repeater lamp - left terminal 2

• If 10 ohms or greater

1. Vehicle 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 10 ohms

6. Connect a test lamp between the appropriate control circuit terminal listed below and ground, vehicle in Service Mode.

* E4N turn signal lamp - left terminal 3

* E4Y turn signal repeater lamp - left terminal 1

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. Vehicle 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. Vehicle OFF, disconnect the X5 harness connector at the K9 body control module, vehicle in Service Mode.

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 appropriate turn signal lamp - left.

DTC B3949

1. Vehicle OFF, disconnect the X2 harness connector at the K9 body control module, vehicle in Service Mode.

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. Vehicle OFF.

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. Vehicle OFF.

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. Vehicle OFF, connect the X2 harness connector at the K9 body control module.

4. Vehicle OFF, exterior lamps OFF, disconnect the harness connectors at the components listed below.

* E4P turn signal lamp - right

* E4Z turn signal repeater lamp - right

5. Test for less than 10 ohms between the ground circuit terminals listed below and ground.

* E4P turn signal lamp - right terminal 1

* E4Z turn signal repeater lamp - right terminal 2

• If 10 ohms or greater

1. Vehicle 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 10 ohms

6. Connect a test lamp between the appropriate control circuit terminal listed below and ground, vehicle in Service Mode.

* E4P turn signal lamp - right terminal 3

* E4Z turn signal repeater lamp - right terminal 1

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. Vehicle 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. Vehicle OFF, disconnect the X4 harness connector at the K9 body control module, vehicle in Service Mode.

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 appropriate turn signal lamp - right.

Repair Instructions

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

* Front Turn Signal Lamp Replacement Service and Repair

* Outside Rearview Mirror Turn Signal Lamp Replacement Outside Rearview Mirror Turn Signal Lamp Replacement

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

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