B3948

DTC B3948

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B3948 02
- Left Front Turn Signal Circuit Short to Ground Short to Ground

DTC B3948 05
- Left Front Turn Signal Circuit Short to Battery or Open

Circuit/System Description

The body control module (BCM) controls the left front turn signal, hazard lamp, and daytime running lamp (DRL). The BCM supplies voltage to control the lighting functions. The BCM monitors the left turn signal lamp supply voltage circuit for proper operation.

Conditions for Setting the DTC

B3948 02

This DTC will set if there is a short to ground in the left front turn signal circuit.

B3948 05

This DTC will set if there is an open or short to voltage in the left front turn signal circuit.

Action Taken When the DTC Sets

* The Service Vehicle Soon message will be displayed.
* Stores a DTC B3948 in the BCM memory.
* If failure is open, short to ground, or to power, rear turn signal flashes at double rate.

Conditions for Clearing the DTC

* This DTC requires an ignition cycle in order to change from current to history.
* The BCM no longer detects continuous battery voltage on the left turn signal monitor circuit for longer than 5 seconds.
* A history DTC will clear after 50 consecutive ignition cycles if the condition for the malfunction is no longer present.

Diagnostic Aids

* The following conditions may cause an intermittent malfunction:

- There is an intermittent short to voltage in the left turn signal monitor circuit.
- The turn signal switch or the hazard switch is shorted internally or is sticking.

* If the BCM detects continuous voltage on the left turn signal monitor circuit, the BCM interprets this as a short to voltage. The BCM will continue with normal DRL operation, and the LF turn signal will remain inoperative.
* A burned out bulb will cause a B3948 05 to set.

Circuit/System Testing

1. Ignition ON, turn signals OFF.
2. Observe the left front turn signal. The turn signal should not be illuminated.

^ If the turn signal is illuminated, test the left turn signal lamps supply voltage circuit for a short to voltage.

3. Test the left turn signal lamps supply voltage circuit for a short to ground or an open/high resistance.
4. If all circuits test normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests