Chevrolet Trax: DTC B3948 OR B3949

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 provides an overview of each diagnostic category.

DTC Descriptors

DTC B3948 01

Left Front Turn Signal Circuit Short to Battery

DTC B3948 02

Left Front Turn Signal Circuit Short to Ground

DTC B3948 04

Left Front Turn Signal Circuit Open

DTC B3949 01

Right Front Turn Signal Circuit Short to Battery

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. The turn signal lamps may only be activated with the ignition switch in the ON or START positions. 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 responds to the turn signal switch input by applying a pulsating voltage to the front and rear turn signal lamps through there respective control 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

• Battery voltage must be between 9-16 V.
• Turn Signal ON.

Conditions for Setting the DTC

DTC B3948 01 and B3948 04

• The BCM detects an open/high resistance in the left front turn signal control circuit.
• The BCM detects an open/high resistance in the left front turn signal ground circuit.
• The BCM detects a short to ground or an open/high resistance in the F7DA (BCM 7) fuse B+ circuit.

DTC B3948 02

The BCM detects a short to ground in the left front turn signal control circuit.

DTC B3949 01 and B3949 04

• The BCM detects an open/high resistance in the right front turn signal control circuit.
• The BCM detects an open/high resistance in the right front turn signal ground circuit.
• The BCM detects a short to ground or an open/high resistance in the F5DA (BCM 5) fuse B+ circuit.

DTC B3949 02

The BCM detects a short to ground in the right front turn signal control circuit.

Actions Taken When the DTC Sets

DTC B3948

• The left front turn signal is inoperative.
• The left turn signal indicator on the instrument cluster flashes rapidly.

DTC B3949

• The right front turn signal is inoperative.
• The right turn signal indicator on the instrument cluster flashes rapidly.

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

When testing at the turn signal lamp bulb socket, make sure all measurements and test lamp connections are in the correct terminal location and do not come in contact with each other during testing.

Reference Information

Schematic Reference

• Exterior Lights Schematics (Encore) , Exterior Lights Schematics (Trax)
• Body Control System Schematics (Encore) , Body Control System Schematics (Trax)

Connector End View Reference

WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - ENCORE WIRING SYSTEMS AND POWER MANAGEMENT - COMPONENT CONNECTOR END VIEWS - INDEX - TRAX

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 scan tool information

Circuit/System Testing

DTC B3948

1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
2. Verify a test lamp illuminates between the B+ circuit terminal 3 and ground.

• If the test lamp does not illuminate and the circuit fuse is good

1. Ignition OFF.
2. Test for less than 2 ohms in the B+ circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse.
• If the test lamp does not illuminate and the circuit fuse is open

1. Ignition OFF.
2. Test for infinite resistance between the B+ circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance, replace the K9 Body Control Module.
• If the test lamp illuminates

3. Ignition OFF, connect the X5 harness connector at the K9 Body Control Module.
4. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate E4 Turn Signal Lamp - Left Front.
5. Test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.

• E4LF Turn Signal Lamp - Left Front socket terminal
• E4Y Turn Signal Repeater Lamp - Left terminal 1
• If 5 ohms or greater

1. Ignition OFF.
2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, repair the open/high resistance in the ground connection.
• If less than 5 ohms

6. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.

• E4LF Turn Signal Lamp - Left Front socket terminal
• E4Y Turn Signal Repeater Lamp - Left terminal 2

7. Verify the test lamp turns ON and OFF when commanding the Left Front Turn Signal Lamp ON and OFF with a scan tool.

• If the test lamp is always OFF

1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit and ground.

• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance

3. Test for less than 2 ohms in the control circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.
• If less than 2 ohms, replace the K9 Body Control Module.
• If the test lamp is always ON

1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.

• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 Body Control Module.
• If the test lamp turns ON and OFF

8. Test or replace the appropriate E4 Turn Signal Lamp Bulb - Left Front.

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