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
--- | --- | --- | --- | ---
Left Turn Signal B+ | 2 | 2 | -- | --
Right Turn Signal B+ | 3 | 3 | -- | --
Left Front Turn Signal Lamp Control | 4 | 4 | 4 | --
Right Front Turn Signal Lamp Control | 5 | 5 | 5 | --
Left Rear Stop/Turn Lamp Control | 6 | 6 | 6 | --
Right Rear Stop/Turn Lamp Control | 7 | 7 | 7 | --
Left Outside Rearview Mirror Turn Signal Control | 8 | 8 | 8 | --
Right Outside Rearview Mirror Turn Signal Control | 8 | 8 | 8 | --
Left Turn Signal Switch Signal | 2 | 2 | 2 | --
Right Turn Signal Switch Signal | 3 | 3 | 3 | --
Turn Signal/Multifunction Switch Ground | -- | 1 | -- | --
LF Park/Turn Signal Lamp Ground | -- | 4 | -- | --
RF Park/Turn Signal Lamp Ground | -- | 5 | -- | --
Left Tail/Stop and Turn Signal Lamp Ground | -- | 6 | -- | --
Right Tail/Stop and Turn Signal Lamp Ground | -- | 7 | -- | --
Left Outside Rearview Mirror Turn Signal Ground | -- | 8 | -- | --
Right Outside Rearview Mirror Turn Signal Ground | -- | 8 | -- | --
1. All Turn Signals Inoperative 2. Left Turn Signals Malfunction 3. Right Turn Signals Malfunction 4. Left Front Turn Signal Malfunction 5. Right Front Turn Signal Malfunction

6. Left Rear Turn Signal Malfunction

7. Right Rear turn Signal Malfunction

8. Outside Rearview Mirror Turn Signal Malfunction.

### Circuit/System Description

The body control module (BCM) controls the vehicle turn signals based on inputs from the turn signal/multifunction switch. With the turn signal/multifunction switch in the left turn position, a ground path is provided on the left turn signal switch signal circuit, indicating a left turn signal request. With the turn signal/multifunction switch in the right turn position, a ground path is provided on the right turn signal switch signal circuit, indicating a right turn signal request. When the specific request is seen, the BCM will pulse the respective turn signal lamp control circuits, illuminating the turn signal lamps.

When a turn signal request is seen by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed.

### 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

1. Ignition ON, view the scan tool Left Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the left turn signal on and off. The parameter should cycle between Active and Inactive.

⇒ | If the parameter does cycle between the specified values, refer to Turn Signal/Multifunction Switch Circuit Malfunction.

2. View the scan tool Right Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the right turn signal on and off. The parameter should cycle between Active and Inactive.

⇒ | If the parameter does cycle between the specified values, refer to Turn Signal/Multifunction Switch Circuit Malfunction.

3. Command the following ON and OFF with a scan tool. The respective turn signal should illuminate.

• | LF Turn Signal

• | RF Turn Signal

• | LR Turn Signal

• | RR Turn Signal

⇒ | If the turn signal does not illuminate, refer to Turn Signal Circuit Malfunction.

4. With the turn signal/multifunction switch in the left turn position, verify the left turn signal indicator is illuminated on the IPC.

⇒ | If the indicator is not illuminated, replace the IPC.

5. With the turn signal/multifunction switch in the right turn position, verify the right turn signal indicator is illuminated on the IPC.

⇒ | If the indicator is not illuminated, replace the IPC.

### Circuit/System Testing

#### Turn Signal/Multifunction Switch Circuit Malfunction

1. Ignition OFF, disconnect the harness connector X1 at the turn signal/multifunction switch.
2. Test for less than 1.0 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 2 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 3 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 2 and the ground circuit terminal 1. 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 3 and the ground circuit terminal 1. 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 Circuit Malfunction

1. Ignition OFF, disconnect the harness connect X4 at the BCM.
2. Ignition ON, verify a test lamp illuminates between the following terminals and ground.

• | B+ terminal 1

• | B+ terminal 3

⇒ | If the test lamp does not illuminate, test the B+ circuit for an open/high resistance. If the circuit fuse is open, test the B+ circuit and the respective turn signal circuits for a short to ground.

3. Ignition OFF, disconnect the harness connector at the affected turn signal lamp.
4. Test for less than 1.0 ohm between the ground circuit and ground.

• | Front turn signal RPO WDA- terminal 2

• | Front turn signal RPO W49/Z88- terminal 1

• | Rear turn signal RPO W49/WDA- terminal B

• | Rear turn signal RPO Z88- terminal D

• | Outside Rearview Mirror RPO W49 - terminal 5, X1

• | Outside Rearview Mirror without RPO W49 - terminal 5, X2

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

5. Connect a test lamp between the control circuit terminal and the ground circuit.

• | Front turn signal RPO WDA- terminal 1

• | Front turn signal RPO W49/Z88- terminal 2

• | Rear turn signal RPO W49/WDA- terminal A

• | Rear turn signal RPO Z88- terminal E

• | Outside Rearview Mirror RPO W49 - terminal 10, X1

• | Outside Rearview Mirror without RPO W49 - terminal 10, X2

6. Ignition ON, command the affected turn signal 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.

7. If all circuits test normal, test or replace the affected turn signal lamp.

### Component Testing

#### Turn Signal/Multifunction Switch

1. Ignition OFF, disconnect the harness connector X1 at the turn signal/multifunction switch.
2. Test for infinite resistance between the following terminals and the ground circuit terminal 1 with the switch in the neutral position.

• | Signal terminal 2

• | Signal terminal 3

⇒ | If not the specified value, replace the turn signal/multifunction switch.

3. Test for less than 2.0 ohms between the signal circuit terminal 2 and the ground circuit terminal E with the switch in the left turn position.

⇒ | If greater than the specified range, replace the turn signal/multifunction switch.

4. Test for less than 2.0 ohms between the signal circuit terminal 3 and the ground circuit terminal E with the switch in the left turn position.

⇒ | If greater than the specified range, replace the turn signal/multifunction switch.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Turn Signal Multifunction Switch Replacement

• | Headlamp Bulb Replacement

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