B3950

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. When the turn signal/multifunction switch is placed in either the turn right or turn left position, ground is applied to the right turn or left turn signal switch signal circuit to the body control module (BCM) and the trailing lighting converter. The BCM and the trailing lighting converter then applies a voltage to the rear turn signal lamps through there respective voltage supply circuits.

Conditions for Running the DTC

B3950 01 and B3951 01

The appropriate turn signal is inactive.

B3950 02, B3950 04, B3951 02 or B3951 04

The appropriate turn signal is active.

Conditions for Setting the DTC

B3950 01 or B3951 01

The control module detects a short to voltage on the control circuit.

B3950 02 or B3951 02

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

B3950 04 or B3951 04

The control module detects an open control circuit.

Action Taken When the DTC Sets

The appropriate turn signal is inoperative.

Conditions for Clearing the DTC

The condition for setting the DTC is not longer present.

Reference Information
Schematic Reference

Exterior Lights Schematics (Exterior Lights Schematics)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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)

Circuit/System Verification

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

Circuit/System Testing

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

* X910 Body Harness & Tail Lamp Left Harness
* X911 Body Harness & Tail Lamp Right Harness

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

* X910 Body Harness & Tail Lamp Left Harness connector terminal 5
* X911 Body Harness & Tail Lamp Right Harness connector terminal 5

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

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

* X910 Body Harness & Tail Lamp Left Harness connector terminal 8
* X911 Body Harness & Tail Lamp Right Harness connector terminal 8

4. 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.

• If the test lamp is always ON, test the Signal circuit for a short to voltage. If the circuit tests normal, replace the appropriate control module.
• 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 appropriate control module.

5. If all the circuits test normal, replace the appropriate tail lamp/liftgate tail lamp.

Repair Instructions

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

* Tail Lamp Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM or trailer lighting converter replacement, setup and programming