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 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 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.
Conditions for Running the DTC
Battery voltage must be between 9-16 V.
Conditions for Setting the DTC
B3948 01
The BCM detects a short to voltage in the Left Front turn signal control circuit.
B3948 02
The BCM detects a short to ground in the Left Front turn signal control circuit.
B3948 04
The BCM detects an open in the Left Front turn signal control circuit.
B3949 01
The BCM detects a short to voltage in the Right Front turn signal control circuit.
B3949 02
The BCM detects a short to ground in the Right Front turn signal control circuit.
B3949 04
The BCM detects an open in the Right Front turn signal control circuit.
Actions Taken When the DTC Sets
B3948 01
The Left Front turn signal lamp will be ON at all times.
B3948 02
The Left Front turn signal lamp will not operate.
B3948 04
The Left Front turn signal lamp will be inoperative.
B3949 01
The Right Front turn signal lamp will be ON at all times.
B3949 02
The Right Front turn signal lamp will not operate.
B3949 04
The Right Front 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 Left Front turn signal bulb. If the bulb is open, DTC B3948 04 will set as current only.
* Check the Right Front turn signal bulb. If the bulb is open, DTC B3949 04 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)
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 Testing
1. Ignition OFF, disconnect the harness connector at the appropriate E4 turn signal lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal 1 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 3 and ground.
4. Command the 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 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.
5. If all circuits test normal, test or replace the E4 turn signal lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Parking and Turn Signal Lamp Bulb Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup, and programming