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 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 panel cluster (IPC) requesting the respective turn signal indicator be pulsed ON and OFF.
Conditions for Running the DTC
Battery voltage must be between 9-16 V.
Conditions for Setting the DTC
DTC B3948 01 and B3948 04
* The BCM detects a short to ground or an open/high resistance in the F31UA (BCM VBATT 07) fuse B+ circuit.
* 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.
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 a short to ground or an open/high resistance in the F3DA (BCM 5) fuse B+ circuit.
* 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.
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 IPC flashes rapidly.
DTC B3949
* The right front turn signal is inoperative.
* The right turn signal indicator on the IPC 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.
Reference Information
Schematic Reference
Exterior Lights Schematics Exterior Lights Schematics
Connector End View Reference
Component Connector End Views Sunshade - Left (D6I)
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 Control Module References for scan tool information
Circuit/System Testing
DTC B3948
1. Ignition OFF, disconnect the X5 harness connector at the K9 BCM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Ignition OFF, connect the X5 harness connector at the K9 BCM.
4. Disconnect the harness connector at the E4N turn signal lamp - left front.
5. Ignition OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal C and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the control circuit terminal B and ground.
7. Ignition ON, command the Left 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 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.
8. If all circuits test normal, replace the E4N turn signal lamp bulb - left front.
DTC B3949
1. Ignition OFF, disconnect the X2 harness connector at the K9 BCM.
2. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
3. Ignition OFF, connect the X2 harness connector at the K9 BCM.
4. Disconnect the harness connector at the E4P turn signal lamp - right front.
5. Ignition OFF, exterior lamps OFF, test for less than 5 ohm between the ground circuit terminal C and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
6. Connect a test lamp between the control circuit terminal B and ground.
7. Ignition ON, command the Right 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 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.
8. If all circuits test normal, replace the E4P turn signal lamp bulb - right front.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Control Module References Control Module References for BCM replacement, setup, and programming