For 1990-2009 cars

### Diagnostic Instructions

1. Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
2. Review Strategy Based Diagnosis for an overview of the diagnostic approach.
3. 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 | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Left Front Turn Signal | B3948 02 | B3948 04 | B3948 01 | --
Right Front Turn Signal | B3949 02 | B3949 04 | B3949 01 | --

### 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 there 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 not longer present.

### Reference Information

#### Schematic Reference

Exterior Lights Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Exterior Lighting Systems Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

Ignition ON, perform the Left Front Turn Signal Lamp test. The left front turn signal lamp and turn signal repeater light should be ON/OFF

Ignition ON, perform 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 Ω 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 (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 Body Control Module (BCM).

5. If all the circuits test normal, replace the appropriate turn signal lamp.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Headlamp Replacement

• | Front Side Turn Signal Lamp Replacement

• | Control Module References for BCM replacement, setup and programming