B3951

DTC B3950 or B3951

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 B3950 01
- Left Rear Turn Signal Circuit Short to Battery

DTC B3950 02
- Left Rear Turn Signal Circuit Short to Ground

DTC B3950 04
- Left Rear Turn Signal Circuit Open

DTC B3951 01
- Right Rear Turn Signal Circuit Short to Battery

DTC B3951 02
- Right Rear Turn Signal Circuit Short to Ground

DTC B3951 04
- Right Rear 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 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 B3950 01 and B3950 04
* The BCM detects an open/high resistance in the left rear stop/turn signal control circuit.
* The BCM detects an open/high resistance in the left rear stop/turn signal ground circuit.

DTC B3950 02

The BCM detects a short to ground in the left rear stop/turn signal control circuit.

DTC B3951 01 and B3951 04
* The BCM detects an open/high resistance in the right rear stop/turn signal control circuit.
* The BCM detects an open/high resistance in the right rear stop/turn signal ground circuit.

DTC B3951 02

The BCM detects a short to ground in the right rear stop/turn signal control circuit.

Actions Taken When the DTC Sets

DTC B3950
* The left rear stop/turn signal is inoperative.
* The left turn signal indicator on the IPC flashes rapidly.

DTC B3951
* The right rear stop/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 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 B3950
1. Vehicle OFF, disconnect the harness connector at the E42L tail lamp assembly - left.
2. Vehicle OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 4 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 1 and ground.
4. Vehicle in Service Mode, command the Left Rear Turn Signal/Brake Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

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

5. If all circuits test normal, replace the E42L tail lamp assembly - left.

DTC B3951
1. Vehicle OFF, disconnect the harness connector at the E42R tail lamp assembly - right.
2. Vehicle OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 4 and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal 1 and ground.
4. Vehicle in Service Mode, command the Right Rear Turn Signal/Brake Lamp ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

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

5. If all circuits test normal, replace the E42R tail lamp assembly - right.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

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