• 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.

Ground is applied at all times to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START positions. 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 responds to the turn signal switch input by applying a pulsating voltage to the front and rear turn signal lamps through there respective control circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument cluster requesting the respective turn signal indicator be pulsed ON and OFF.

Battery voltage must be between 9-16 V.

• The BCM detects an open/high resistance in the left front turn signal control circuit.
• The BCM detects an open/high resistance in the left front turn signal ground circuit.

The BCM detects a short to ground in the left front turn signal control circuit.

• The BCM detects an open/high resistance in the right front turn signal control circuit.
• The BCM detects an open/high resistance in the right front turn signal ground circuit.

The BCM detects a short to ground in the right front turn signal control circuit.

• The left front turn signal is inoperative.
• The left turn signal indicator on the instrument cluster flashes rapidly.

• The right front turn signal is inoperative.
• The right turn signal indicator on the instrument cluster flashes rapidly.

• The condition responsible for setting the DTC no longer exists.
• A history DTC will clear once 100 consecutive malfunction-free ignition cycles have occurred.

When testing at the turn signal lamp bulb sockets, make sure all measurements and test lamp connections are in the correct terminal location and do not come in contact with each other during testing.

Exterior Lights Schematics

Master Electrical Component List

Exterior Lighting Systems Description and Operation

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

Control Module References for scan tool information

1. Ignition OFF, exterior lamps OFF, remove the appropriate E4 Turn Signal Lamp – Left listed below.
• E4LF Turn Signal Lamp – Left Front
• E4Y Turn Signal Repeater Lamp – Left
2. Test for less than 10 Ω between the appropriate ground circuit at the socket terminal and ground.
• If 10 Ω or greater
1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, repair the open/high resistance in the ground connection.
• If less than 10 Ω
3. Connect a test lamp between the appropriate control circuit at the socket terminal and ground, ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the Left Front Turn Signal Lamp ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K9 Body Control Module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X5 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 Body Control Module.
• If the test lamp turns ON and OFF
5. Test or replace the E4 Turn Signal Lamp – Left.

1. Ignition OFF, exterior lamps OFF, remove the appropriate E4 Turn Signal Lamp – Right listed below.
• E4RF Turn Signal Lamp – Right Front
• E4Z Turn Signal Repeater Lamp – Right
2. Test for less than 10 Ω between the appropriate ground circuit at the socket terminal and ground.
• If 10 Ω or greater
1. Ignition OFF.
2. Test for less than 2 Ω in the ground circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, repair the open/high resistance in the ground connection.
• If less than 10 Ω
3. Connect a test lamp between the appropriate control circuit at the socket terminal and ground, ignition ON.
4. Verify the test lamp turns ON and OFF when commanding the Right Front Turn Signal Lamp ON and OFF with a scan tool.
• If the test lamp is always OFF
1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module.
2. Test for infinite resistance between the control circuit and ground.
• If less than infinite resistance, repair the short to ground on the circuit.
• If infinite resistance
3. Test for less than 2 Ω in the control circuit end to end.
• If 2 Ω or greater, repair the open/high resistance in the circuit.
• If less than 2 Ω, replace the K9 Body Control Module.
• If the test lamp is always ON
1. Ignition OFF, disconnect the X4 harness connector at the K9 Body Control Module, ignition ON.
2. Test for less than 1 V between the control circuit terminal and ground.
• If 1 V or greater, repair the short to voltage on the circuit.
• If less than 1 V, replace the K9 Body Control Module.
• If the test lamp turns ON and OFF
5. Test or replace the appropriate E4 Turn Signal Lamp – Right.

Perform the Diagnostic Repair Verification after completing the repair.

• Outside Rearview Mirror Turn Signal Lamp Replacement
• Turn Signal Bulb Replacement - Left Side
• Turn Signal Bulb Replacement - Right Side
• Control Module References for BCM replacement, programming, and setup