For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Review Strategy Based Diagnosis for an overview of the diagnostic approach.

• | 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 05: Left Front Turn Signal Circuit Open or Short to Voltage
DTC B3949 02: Right Front Turn Signal Circuit Short to Ground
DTC B3949 05: Right Front Turn Signal Circuit Open or Short to Voltage

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Hazard Switch Signal | 2 | 2 | 2 | --
Left Turn Signal Switch Signal | 1 | 1 | -- | --
Right Turn Signal Switch Signal | 1 | 1 | -- | --
Right Rear Stop/Turn Signal Lamp Control | B3951 02 | B3951 05 | B3951 05 | --
Left Front Turn Signal Lamp Control | B3948 02 | B3948 05 | B3948 05 | --
Right Front Turn Signal Lamp Control | B3949 02 | B3949 05 | B3949 05 | --
Left Rear Stop/Turn Signal Lamp Control | B3950 02 | B3950 05 | B3950 05 | --
Left Rear Stop/Turn Lamp Ground | -- | 1 | -- | --
Right Rear Stop/Turn Lamp Ground | -- | 1 | -- | --
Turn Signal/Multifunction Switch Ground | -- | 1 | -- | --
Turn Signal Lamp - LF Ground | -- | 1 | -- | --
Turn Signal Lamp - RF Ground | -- | 1 | -- | --
1. Turn Signal Lamps and/or Indicators Malfunction 2. Hazard Lamps Malfunction

### Circuit/System Description

Ground is applied at all times at G300 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. 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 pulsating voltage to the front and rear turn signal lamps through there respective voltage supply circuits. Ground for the left front turn signal lamp is supplied at G101. Ground for the right front turn signal lamp is supplied at G102. Ground for the left rear turn signal lamp is supplied at G400. Ground for the right rear turn signal lamp is supplied at G402.

### Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

### Conditions for Setting the DTC

#### B3948 02

This DTC will set when the BCM detects a short to ground in the LF turn signal voltage supply circuit.

#### B3948 05

This DTC will set when the BCM detects a short to voltage or an open/high resistance in the LF turn signal voltage supply circuit.

#### B3949 02

This DTC will set when the BCM detects a short to ground in the RF turn signal voltage supply circuit.

#### B3949 05

This DTC will set when the BCM detects a short to voltage or an open/high resistance in the RF turn signal voltage supply circuit.

### Actions Taken When the DTC Sets

#### B3948 02

When this DTC is present, the LF turn signal lamp will not operate.

#### B3948 05

When this DTC is present, the LF turn signal lamp will be ON at all times for a short to voltage condition. For an open condition, the LF turn signal lamp will be inoperative.

#### B3949 02

When this DTC is present, the RF turn signal lamp will not operate.

#### B3949 05

When this DTC is present, the RF turn signal lamp will be ON at all times for a short to voltage condition. For an open condition, the RF turn signal lamp will be inoperative.

### 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.

### Diagnostic Aids

#### B3948 05

Check the LF turn signal bulb. If the bulb is open, this DTC will set as current only.

#### B3949 05

Check the RF turn signal bulb. If the bulb is open, this DTC will set as current only.

### 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 Testing

1. Ignition OFF, disconnect the harness connector at the appropriate turn signal lamp.
2. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the ground circuit terminal G and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit terminal A and ground.
4. Command the appropriate 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 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 BCM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Parking and Turn Signal Lamp Replacement

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