B3948

DTC B3948 or B3949

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 B3948 02
- Left Front Turn Signal Circuit Short to Ground

DTC B3948 04
- Left Front Turn Signal Circuit Open

DTC B3949 02
- Right Front Turn Signal Circuit Short to Ground

DTC B3949 04
- Right Front 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 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 and side signal lamps through their respective voltage supply circuits.

Conditions for Running the DTC

The appropriate turn signal is active.

Conditions for Setting the DTC

B3948 02 and B3949 02

The BCM detects a short to ground on the appropriate front turn signal control circuit.

B3948 04 and B3949 04

The BCM detects an open circuit on the appropriate front turn signal 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 (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

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Ignition ON, command the appropriate Front Turn Signal Lamp ON and OFF with a scan tool. The appropriate front turn signal lamp and turn signal repeater light should be turn ON and OFF when changing between the commanded states.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate front turn signal lamp.
2. Test for less than 5 ohm between the ground circuit terminal listed below and ground.

* E4 Front Turn Signal Lamp - terminal 1
* E4 Turn Signal Repeater Lamp - terminal 2

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

3. Connect a test lamp between the control circuit terminal listed below and ground.

* E4 Front Turn Signal Lamp - terminal 5
* E4 Turn Signal Repeater Lamp - terminal 1

4. Command the appropriate Front 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 signal circuit for a short to voltage. If the circuit tests normal, replace the K9 BCM.
• 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 BCM.

5. If all the circuits test normal, replace the front turn signal lamp.

Repair Instructions

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

* Front Turn Signal Lamp Bulb Replacement (TT2) (Front Turn Signal Lamp Bulb Replacement (TT2))Front Turn Signal Lamp Bulb Replacement (TT4) (Front Turn Signal Lamp Bulb Replacement (TT4))
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming