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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 02
- Left Rear Turn Signal Circuit Short to Ground

DTC B3950 05
- Left Rear Turn Signal Circuit Short to Battery or Open

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

DTC B3951 05
- Right Rear Turn Signal Circuit Short to Battery or Open

Diagnostic Fault Information





Circuit/System Description

Ground is applied at all times at G201 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 (BCM) 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 their respective control circuits. Ground for the left rear turn signal lamp is supplied at G401. Ground for the right rear turn signal lamp is supplied at G402.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

B3950 02

This DTC will set when the BCM detects a short to ground in the LR turn signal control circuit.

B3950 05

This DTC will set when the BCM detects a short to voltage or an open in the LR turn signal control circuit.

B3951 02

This DTC will set when the BCM detects a short to ground in the RR turn signal control circuit.

B3951 05

This DTC will set when the BCM detects a short to voltage or an open in the RR turn signal control circuit.

Actions Taken When the DTC Sets

B3950 02

When this DTC is present, the LR turn signal lamp will not operate.

B3950 05

When this DTC is present, the LR turn signal lamp will be ON at all times for a short to voltage condition. For an open condition, the LR turn signal lamp will be inoperative.

B3951 02

When this DTC is present, the RR turn signal lamp will not operate.

B3951 05

When this DTC is present, the RR turn signal lamp will be ON at all times for a short to voltage condition. For an open condition, the RR turn signal lamp will be inoperative.

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 ignition cycles have occurred.

Diagnostic Aids

* Check the LR turn signal bulb. If the bulb is open, DTC B3950 05 will set as current only.
* Check the RR turn signal bulb. If the bulb is open, DTC B3951 05 will set as current only.

Reference Information
Schematic Reference

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

Component Connector End Views (Connector Views)
Description and Operation

Exterior Lighting Systems Description and Operation (Exterior Lighting Systems Description and Operation)
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

Programming and Relearning (Programming and Relearning) for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate rear turn signal lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal C 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 A and ground.
4. Command the appropriate rear Stop/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 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 BCM.

5. If all circuits test normal, test or replace the appropriate turn signal lamp assembly.

Repair Instructions

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

* Tail Lamp Replacement (Service and Repair)
* Programming and Relearning (Programming and Relearning) for BCM replacement, setup, and programming