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. 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/side and rear turn signal lamps through their respective voltage supply circuits.
Conditions for Running the DTC
B3948 01 and B3949 01
The appropriate turn signal is inactive.
B3948 02, B3948 04, B3949 02 and B3949 04
The appropriate turn signal is active.
Conditions for Setting the DTC
B3948 01 and B3949 01
The BCM detects a short to voltage on the control circuit.
B3948 02 and B3949 02
The BCM detects a short to ground on the control circuit.
B3948 04 and B3949 04
The BCM detects an open control circuit.
Action Taken When the DTC Sets
The appropriate turn signal 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 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 Left Front Turn Signal Lamp test. The left front turn signal lamp and turn signal repeater light should be ON/OFF.
Ignition ON, command the Right Front Turn Signal Lamp test. The right front turn signal lamp and turn signal repeater light should be ON/OFF.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.
2. Test for less than 5 ohm between the appropriate turn signal lamp ground circuit harness connector listed below and ground.
* E4LF Turn Signal Lamp - Left Front ground circuit harness connector terminal 2
* E4Y Turn Signal Repeater Lamp - Left ground circuit harness connector terminal 2
* E4RF Turn Signal Lamp - Right Front ground circuit harness connector terminal 2
* E4Z Turn Signal Repeater Lamp - Right ground circuit harness connector terminal 2
• If greater than the specified value, test the ground circuit for an open/high resistance.
3. Connect a test lamp between the appropriate turn signal lamp control circuit harness connector listed below and ground.
* E4LF Turn Signal Lamp - Left Front circuit harness connector terminal 1
* E4Y Turn Signal Repeater Lamp - Left circuit harness connector terminal 1
* E4RF Turn Signal Lamp - Right Front circuit harness connector terminal 1
* E4Z Turn Signal Repeater Lamp - Right circuit harness connector terminal 1
4. Command the appropriate 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 signal circuit for a short to voltage. If the circuit tests normal, replace the K9 Body Control Module.
• 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 Body Control Module.
5. If all the circuits test normal, replace the appropriate turn signal lamp.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Headlamp Replacement (Service and Repair)
* Front Side Turn Signal Lamp Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for BCM replacement, setup and programming