For 1990-2009 cars

### Diagnostic Instructions

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

• | Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Turn Signal Ground Circuit | 1 | 1 | -- | --
Turn Signal Switch | 1 | 1 | -- | --
1. Turn Signal Lamps and/or Indicators Inoperative

### Circuit/System Description

Voltage runs through the left and right turn signal fuses of the instrument panel I/P fuse block, then through the body control module BCM, before reaching the turn signal multifunction switch. When the turn signal switch is engaged, the switch closes and supplies voltage to the front and rear park/turn signal lamps.

### Diagnostic Aids

• | An open/high resistance or a short to ground in the turn signal multifunction switch would cause the turn signal lamps to become inoperative.

• | There are certain relays that are PCB or soldered to the underhood fuseblock circuit board and any relay replacement would warrant a replacement of the underhood fuseblock.

• | This vehicle is not equipped with a turn signal relay.

### Reference Information

#### Schematic Reference

• | Exterior Lights Schematics

• | Displays and Gages Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data Definitions

• | Scan Tool Data List

• | Scan Tool Output Controls

### Circuit/System Verification

Ignition ON, observe right or left turn signal while engaging the turn signal multifunction switch in the appropriate position. The selected bulbs should illuminate.

### Circuit/System Testing

#### Turn Signal Multifunction Switch Circuit Testing

1. Ignition OFF, disconnect the harness connector at the turn signal multifunction switch.
2. Ignition ON, install a test lamp between the turn signal voltage supply circuit and ground. The test lamp should flash ON and OFF.

⇒ | If the test lamp does not flash, test the voltage supply circuit for a short to ground or an open/high resistance.

3. Install a 3-amp fused jumper wire between the voltage supply circuit and the turn signal circuit. Verify that the proper turn signal lamps are ON.

⇒ | If the turn signals are not ON, test the signal circuit of the turn signal multifunction switch for a short to voltage, short to ground or an open/high resistance.

4. If all circuits test normal, test or replace the turn signal multifunction switch.

#### Park/Turn Signal/Turn Signal Indicator Circuit Testing

1. Ignition OFF, remove the inoperative light bulb.
2. Test for less than 1.0 ohm of resistance between the ground circuit and ground.

⇒ | If greater than 1.0 ohm, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit and the ground circuit.
4. Ignition ON, turn ON the appropriate turn signal, the test lamp should flash.

⇒ | If the test lamp remains ON all the time, test for a short to voltage on the control circuit . If the circuit tests normal, test or replace the BCM.

⇒ | If the test lamp remains OFF all the time, test for a short to ground or an open/high resistance on the control circuit. If the circuit tests normal, test or replace the turn signal multifunction switch.

5. If all circuits test normal, test or replace the light bulb.

#### Instrument Panel (I/P) Circuit Testing

1. Ignition OFF, disconnect the harness connector at the I/P.
2. Test for less than 1.0 ohm of resistance between the ground circuit and ground.

⇒ | If greater than 1.0 ohm, test the ground circuit for an open/high resistance.

3. Connect a test lamp between the control circuit and the ground circuit.
4. Ignition ON, turn ON the appropriate turn signal. The test lamp should flash.

⇒ | If the test lamp remains ON all the time, test for a short to voltage on the control circuit. If the circuit tests normal, test or replace the BCM.

⇒ | If the test lamp remains OFF all the time, test for a short to ground or an open/high resistance on the control circuit. If the circuit tests normal, test or replace the turn signal multifunction switch.

5. If all circuits test normal, replace the I/P.

### Component Testing

#### Turn Signal Switch Testing

1. Ignition OFF, disconnect the harness connector at the turn signal multifunction switch.
2. Test for infinite resistance between the signal terminals C2 pins G and H and the voltage supply terminal C1 pin 3 with the turn signal multifunction switch in the open position.

⇒ | If less than infinite resistance, replace the turn signal multifunction switch.

3. Test for less than 1.5 ohms between the signal terminals C2 pins G and H and the voltage supply terminal C1 pin 3 with the switch in the closed position.

⇒ | If greater than 1.5 ohms, replace the turn signal multifunction switch.

#### Park/Turn Signal/Turn Signal Indicator Bulb Testing

1. Ignition OFF, remove the appropriate light bulb.
2. Test for less than 4.5 ohms between the two terminals 1 and 2 on the light bulb.

⇒ | If greater than 4.5 ohms, replace the light bulb.

### Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Park/Turn Signal Lamp Bulb Replacement

• | Turn Signal Multifunction Switch Replacement

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

• | Instrument Cluster Replacement