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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
CTSY/TRN SIG RT FRT Fuse B+ | 1 | 1 | -- | --
TRN/SIG RT Fuse B+ | 1 | 1 | -- | --
TRN/SIG LT Fuse B+ | 1 | 1 | -- | --
Left Turn Signal Switch Signal | 2 | 2 | 2 | --
Right Turn Signal Switch Signal | 2 | 2 | 2 | --
Left Front Turn Signal Lamp Control | 1 | 1 | 1 | --
Right Front Turn Signal Lamp Control | 1 | 1 | 1 | --
Left Rear Turn Lamp Control | 1 | 1 | 1 | --
Right Rear Turn Lamp Control | 1 | 1 | 1 | --
Left Rear Turn Lamp Ground | -- | 1 | -- | --
Left Repeater Lamp Ground | -- | 1 | -- | --
Right Repeater Lamp Ground | -- | 1 | -- | --
Right Rear Turn Lamp Ground | -- | 1 | -- | --
Turn Signal/Multifunction Switch Ground | -- | 2 | -- | --
Turn Signal Lamp - LF Ground | -- | 1 | -- | --
Turn Signal Lamp - RF Ground | -- | 1 | -- | --
1. Turn Signal Lamps and/or Indicators Malfunction 2. Turn Signal Switch Malfunction

### Circuit/System Description

Ground is applied at all times at G201 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. When a turn signal request is received by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed ON and OFF.

### 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, observe the scan tool Right and Left Turn Signal Switch parameters while cycling the turn signal switch between the left and right positions. The parameters should change between Active and Inactive.

⇒ | If the parameters do not change between the commanded states, refer to Turn Signal Switch Malfunction.

⇒ | If the parameters change between the commanded states, refer to Turn Signal Lamps Malfunction.

### Circuit/System Testing

#### Turn Signal Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the turn signal/multifunction switch.
2. Ignition OFF, test for less than 1 ohm between the ground circuit terminal 1 and ground.

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

3. Ignition ON, verify the scan tool Left Turn Signal Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 8 for a short to ground. If the circuit tests normal, replace the BCM.

4. Verify the scan tool Right Turn Signal Switch parameter is Inactive.

⇒ | If not the specified value, test the signal circuit terminal 7 for a short to ground. If the circuit tests normal, replace the BCM.

5. Install a 3A fused jumper wire between the signal circuit terminal 8 and ground. Verify the scan tool Left Turn Signal Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

6. Install a 3A fused jumper wire between the signal circuit terminal 7 and ground. Verify the scan tool Right Turn Signal Switch parameter is Active.

⇒ | If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the BCM.

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

#### Turn Signal Lamps Malfunction

1. Ignition OFF, disconnect the X4 harness connector at the BCM.
2. Verify that a test lamp illuminates between the B+ circuit terminal 1 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

3. Verify that a test lamp illuminates between the B+ circuit terminal 2 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

4. Verify that a test lamp illuminates between the B+ circuit terminal 3 and ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

5. Ignition OFF, connect the X4 harness connector at the BCM.
6. Ignition OFF, disconnect the harness connector at the inoperative turn signal lamp.
7. Ignition OFF, exterior lamps OFF, test for less than 5 ohms between the appropriate ground circuit terminal listed below and ground.

• | Left front turn signal terminal 1

• | Right front turn signal terminal 1

• | Left rear turn signal terminal 2

• | Right rear turn signal terminal 2

• | Left turn signal repeater terminal 1

• | Right turn signal repeater terminal 1

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

8. Connect a test lamp between the appropriate control circuit terminal listed below and ground.

• | Left front turn signal terminal 9

• | Right front turn signal terminal 9

• | Left rear turn signal terminal 6

• | Right rear turn signal terminal 6

• | Left turn signal repeater terminal 2

• | Right turn signal repeater terminal 2

9. Command the appropriate Turn Signal 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 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.

10. If all circuits test normal, replace the inoperative turn signal lamp assembly.

#### Turn Signal Indicators Malfunction

Ignition ON, with a scan tool perform the Display Tests for the instrument panel cluster (IPC) and observe the turn signal lamp indicators.

⇒ | If the turn signal lamp indicators illuminate during the test, replace the BCM.

⇒ | If the turn signal lamp indicators do not illuminate during the test or remain illuminated at all times, replace the IPC.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Parking and Turn Signal Lamp Replacement

• | Repeater Lamp Replacement

• | Tail Lamp Assembly and /or Backup, Sidemarker, Stop, Turn Signal Bulb Replacement

• | Turn Signal Switch Replacement

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