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

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

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 position. 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 through either the right turn or left turn signal switch signal circuit. The BCM then applies a pulsating voltage to the front and rear turn signal lamps through there respective voltage supply circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective turn signal indicator be pulsed ON and OFF.

Conditions for Running the DTC

The appropriate turn signal is active

Conditions for Setting the DTC

The BCM detects a short to ground on the rear turn signal control circuit

Action Taken When the DTC Sets

The appropriate rear turn signal will be inoperative.

Conditions for Clearing the DTC

* The DTC will be current for as long as the fault is present.
* When the fault is no longer present, the DTC will be a history DTC.
* A history DTC will clear after 50 ignition cycles.

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

1. Ignition ON, command the Left Rear Turn Signal Lamp ON and OFF with a scan tool. The left rear turn signal lamp should turn ON and OFF when changing between the commanded states.
2. Command the Right Rear Turn Signal Lamp ON and OFF with a scan tool. The right rear turn signal lamp should turn ON and OFF when changing between the commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the X2 harness connector K9 BCM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance

3. Ignition OFF, connect the X2 harness connector K9 BCM.
4. Ignition OFF, disconnect the X2 harness connector at the appropriate E4 turn signal lamp-rear.
5. Test for less than 30 ohm between the ground circuit terminal 1 and ground.

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

6. Connect a test lamp between the control circuit terminal 3 and ground.
7. Command the appropriate Rear Turn Signal 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 circuit tests normal, replace the K9 BCM.

8. If all the circuits test normal, replace the bulb or E4 turn signal lamp-rear.

Repair Instructions

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

* Rear Turn Signal Lamp Bulb Replacement (Rear Turn Signal Lamp Bulb Replacement)
* Control Module References (Programming and Relearning) for BCM replacement, programming and setup