B3949
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
The BCM detects a short to ground on the left front turn signal control circuit.
B3948 04
The BCM detects an open/high resistance on the left front turn signal control circuit.
B3949 02
The BCM detects a short to ground on the right front turn signal control circuit.
B3949 04
The BCM detects an open/high resistance on the right front turn signal control circuit.
Action Taken When the DTC Sets
B3948 02 or B3948 04
The left front turn signal will be inoperative.
B3949 02 or B3949 04
The right front 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.
Diagnostic Aids
The vehicle may be equipped with the RPO DLG/DLL driver and passenger outside rearview mirrors which contains turn signal repeater lamps, the lamps share the same control circuits as the front park/turn signal lamps.
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 for scan tool information
Circuit/System Verification
Ignition ON, command the Front Turn Signal Lamp ON and OFF with a scan tool. The appropriate front turn signal lamp should turn ON and OFF while changing between the commanded states.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the appropriate E4 turn signal lamp.
2. Test for less than 30 ohms between the ground circuit terminal listed below and ground:
* Turn signal lamp - front - terminal 1
* 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:
* Turn signal lamp - front - terminal 5
* 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 circuits test normal, replace the E4 turn signal lamp.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
* Front Side Turn Signal Lamp Replacement Service and Repair
* Front Turn Signal Lamp Bulb Replacement Service and Repair
* Outside Rearview Mirror Replacement Outside Rearview Mirror Replacement
* Control Module References Programming and Relearning for BCM replacement, programming and setup