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DTC B3950 or B3951

DTC B3950 or B3951

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 has overviews of all diagnostic categories.


DTC Descriptors

DTC B3950 02

Left Rear Turn Signal Circuit Short to Ground

DTC B3950 04

Left Rear Turn Signal Circuit Open

DTC B3951 02

Right Rear Turn Signal Circuit Short to Ground

DTC B3951 04

Right Rear Turn Signal Circuit Open

Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performance
Left Rear Turn Signal

B3950 02

B3950 04

1

-

Right Rear Turn Signal

B3951 02

B3951 04

1

-

1. Rear Turn Signal Always ON



Circuit/System Description

Ground is applied at all times to the turn signal/multifunction switch. 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 then applies a voltage to the front/side and rear turn signal lamps through their respective voltage supply circuits.

Conditions for Running the DTC

The appropriate turn signal is active.

Conditions for Setting the DTC

B3950 02 or B3951 02

The BCM detects a short to ground on the control circuit.

B3950 04 or B3951 04

The BCM detects an open control circuit.

Action Taken When the DTC Sets

The appropriate turn signal lamp is inoperative.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Exterior Lights Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exterior Lighting Systems 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 information on diagnostic tools

Circuit/System Verification

Ignition ON, perform the appropriate Rear Turn Signal/Hazard Lamp test. The appropriate rear turn signal/hazard lamp should be ON/OFF.

Circuit/System Testing


1. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp listed below:

• E5E Tail Lamp - Left harness connector X1

• E5F Tail Lamp - Right harness connector X1

2. Test for less than 5 Ω between the appropriate turn signal lamp ground circuit harness connector listed below and ground.

• E5F Tail Lamp - Right ground circuit harness connector terminal F

• E5E Tail Lamp - Left ground circuit harness connector terminal F

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

4. Connect a test lamp between the appropriate turn signal lamp control circuit harness connector listed below and ground.

• E5F Tail Lamp - Right Turn Signal Lamp circuit harness connector terminal B

• E5E Tail Lamp - Left Turn Signal Lamp circuit harness connector terminal B

5. Command the appropriate Turn Signal Lamp test ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

6. If the test lamp is always ON, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.

7. If the test lamp is always OFF, test the signal circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the K9 Body Control Module.

8. If all the circuits test normal, replace the appropriate turn signal lamp.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Tail Lamp Replacement

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