Skip to content
Tahoe / Yukon Service Manual

Turn Signal Lamps and_or Indicators Malfunction

Turn Signal Lamps and/or Indicators Malfunction 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 number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
2915 Signal 1 1 1 —
2916 Signal 1 1 1 —
6568 Signal 2 2 2 —
7545 Signal 2 2 2 —
1314 Control B1998 11 3 3 —
1315 Control B1999 11 3 3 —
2114 Control B199C 11 3 3 —
2115 Control B199D 11 3 3 —
1334 Control B199A 11 B199A 13 B199A 11, B199A 13 —
1335 Control B199B 11 B199B 13 B199B 11, B199B 13 —
* Ground — 2, 3 — —
1. Turn Signal Switch Malfunction 2. Turn Signal Lamp Outage Detection Malfunction 3. Turn Signal Lamp Malfunction *. Refer to the schematic for information on specific ground circuits

Scan Tool Functions K9 Body Control Module – Data Display – Front Exterior Lighting Data Control Function Description

Control Function Description
Left Turn Signal Switch This data parameter will show the status of the turn signal switch as Active/Inactive when the turn signal switch is placed in the left turn position and back.
Right Turn Signal Switch This data parameter will show the status of the turn signal switch as Active/Inactive when the turn signal switch is placed in the right turn position and back.

K219 Lighting Control Module – Control Functions – Exterior Lighting

Control Function Description
Left Front Turn Signal Lamp Command This control function will control the left front turn signal lamp on/off
Right Front Turn Signal Lamp Command This control function will control the right front turn signal lamp on/off
Left Turn Signal Repeater Lamp Command This control function will control the left mirror turn signal lamp on/off
Right Turn Signal Repeater Lamp Command This control function will control the right mirror turn signal lamp on/off
Left Rear Turn Signal Lamp This control function will control the left rear turn signal lamp on/off
Right Rear Turn Signal Lamp This control function will control the right rear turn signal lamp on/off

Circuit/System Description Turn Signals The K9 Body Control Module (BCM) provides the S78 Turn Signal Switch with left turn signal circuit  2915 and right turn signal circuit 2916. 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 BCM through either the right turn or left turn signal switch signal circuit. The BCM responds to the turn signal switch input by sending a serial data message to the K219 Lighting Control Module. The lighting control module responds by applying a pulsating voltage to the front, mirror, 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 also sent to the instrument cluster requesting the respective turn signal indicator be pulsed ON and OFF. Turn Signal Outage Detection Due to the high impedance of light emitting diodes (LEDs), vehicles with LED turn signals require outage detection circuits that provide turn signal feedback to the lighting control module. The lighting control module uses the feedback information to send a serial data message to the instrument cluster to alert the driver anytime a turn signal fault is detected. A fault on the turn signal outage detection circuit will result in the turn signals on that side of the vehicle flashing at a rapid rate. Reference Information Schematic Reference Exterior Lights Schematics Connector End View Reference Master Electrical Component List 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/vehicle in service mode, verify the scan tool Left/Right Turn Signal Switch data parameter changes between Active/Inactive when placing the turn signal switch in the left/right positions. ⇒ If parameters do not change Refer to Circuit/System Testing – Turn Signal Switch Malfunction. ⇓ If parameters change
  2. Verify each turn signal lamp turns on and off when commanding the turn signal lamp ON/OFF with the appropriate scan tool control function: Left Front Turn Signal Lamp Command = the left front turn signal Right Front Turn Signal Lamp Command = the right front turn signal Left Turn Signal Repeater Lamp Command = the left mirror turn signal Right Turn Signal Repeater Lamp Command = the right mirror turn signal Left Rear Turn Signal Lamp = the left rear turn signal lamp Right Rear Turn Signal Lamp = the right rear turn signal lamp ⇒ If one or more of the turn signals do not turn ON and OFF Refer to Circuit/System Testing – Turn Signal Lamps Malfunction. ⇓ If all of the turn signal lamps turn ON and OFF
  3. Verify all of the turn signals flash at a normal rate while commanding the turn signals ON and OFF with the turn signal switch. ⇒ If the turn signals flash at a rapid rate Refer to Circuit/System Testing – Turn Signal Lamps Outage Detection Malfunction. ⇓ If the turn signals flash at a normal rate
  4. A fault is not currently present and may be an intermittent condition. Circuit/System Testing Turn Signal Switch Malfunction
  5. Ignition/vehicle OFF, disconnect the connector at the S78 Turn Signal Switch.
  6. Verify a test lamp illuminates between ground circuit terminal 3 and B+. ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on circuit 1850 or the ground connection. ⇓ If the test lamp illuminates
  7. Ignition on/vehicle in service mode, test for 7 – 8 V between the appropriate signal circuit terminal and ground: Left turn signal = Terminal 1 Right turn signal = Terminal 2 ⇒ If less than 7 V 3.1. Test the appropriate circuit for a short to ground: Left turn signal = Circuit 2915. Right turn signal = Circuit 2916. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 3.2. Test the appropriate circuit for an open/high resistance: Left turn signal = Circuit 2915. Right turn signal = Circuit 2916. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 3.3. Replace the K9 Body Control Module. ⇒ If greater than 8 V 3.1. Test the appropriate circuit for a short to voltage: Left turn signal = Circuit 2915. Right turn signal = Circuit 2916. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 3.2. Replace the K9 Body Control Module. ⇓ If 7 – 8 V
  8. Replace the S78 Turn Signal Switch. Turn Signal Lamps Malfunction
  9. Ignition OFF, disconnect the connector at the appropriate component with the inoperative turn signal: E13LA Front Headlamp - Left E13RA Front Headlamp - Right A9A Outside Rearview Mirror – Driver A9B Outside Rearview Mirror – Passenger E42L Rear Body Structure Stop Lamp - Left E42R Rear Body Structure Stop Lamp - Right  2. Verify a test lamp illuminates between the appropriate ground circuit terminal and B+: E13LA Front Headlamp - Left = Terminal 1 E13RA Front Headlamp - Right = Terminal 1 A9A Outside Rearview Mirror – Driver = Terminal 9 A9B Outside Rearview Mirror – Passenger = Terminal 9 E42L Rear Body Structure Stop Lamp - Left = Terminal 1 E42R Rear Body Structure Stop Lamp - Right = Terminal 1 ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on the ground circuit or ground connection. ⇓ If the test lamp illuminates
  10. Connect a test lamp between the appropriate control circuit terminal and ground. E13LA Front Headlamp - Left = Terminal 6 E13RA Front Headlamp - Right = Terminal 6 A9A Outside Rearview Mirror – Driver = Terminal 8 A9B Outside Rearview Mirror – Passenger = Terminal 8 E42L Rear Body Structure Stop Lamp - Left = Terminal 5 E42R Rear Body Structure Stop Lamp - Right = Terminal 5
  11. Ignition on/vehicle in service mode, verify the test lamp turns on and off when commanding the appropriate turn signals on and off with a scan tool: Left Front Turn Signal Lamp Command = the left front turn signal Right Front Turn Signal Lamp Command = the right front turn signal Left Turn Signal Repeater Lamp Command = the left mirror turn signal Right Turn Signal Repeater Lamp Command = the right mirror turn signal Left Rear Turn Signal Lamp = the left rear turn signal lamp Right Rear Turn Signal Lamp = the right rear turn signal lamp ⇒ If the test lamp is always off 4.1. Test the appropriate control circuit for a short to ground: E13LA Front Headlamp - Left = Circuit 1314 E13RA Front Headlamp - Right = Circuit 1315 A9A Outside Rearview Mirror – Driver = Circuit 2114 A9B Outside Rearview Mirror – Passenger = Circuit 2115 E42L Rear Body Structure Stop Lamp - Left = Circuit 1334 E42R Rear Body Structure Stop Lamp - Right = Circuit 1335 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Test the appropriate control circuit for an open/high resistance: E13LA Front Headlamp - Left = Circuit 1314 E13RA Front Headlamp - Right = Circuit 1315 A9A Outside Rearview Mirror – Driver = Circuit 2114 A9B Outside Rearview Mirror – Passenger = Circuit 2115 E42L Rear Body Structure Stop Lamp - Left = Circuit 1334 E42R Rear Body Structure Stop Lamp - Right = Circuit 1335 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 4.3. Replace the K219 Lighting Control Module. ⇒ If the test lamp is always on 4.1. Test the appropriate control circuit for a short to voltage: E13LA Front Headlamp - Left = Circuit 1314 E13RA Front Headlamp - Right = Circuit 1315 A9A Outside Rearview Mirror – Driver = Circuit 2114 A9B Outside Rearview Mirror – Passenger = Circuit 2115 E42L Rear Body Structure Stop Lamp - Left = Circuit 1334 E42R Rear Body Structure Stop Lamp - Right = Circuit 1335 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 4.2. Replace the K219 Lighting Control Module. ⇓ If the test lamp turns on and off
  12. Replace the appropriate turn signal. Turn Signal Lamp Outage Detection Malfunction
  1. Ignition/vehicle OFF, disconnect the appropriate component: E13LA Front Headlamp - Left E13RA Front Headlamp - Right
  2. Verify a test lamp illuminates between ground circuit terminal 1 and B+. ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on the ground circuit or ground connection. ⇓ If the test lamp illuminates
  3. Ignition on/vehicle in service mode, test for 8 V or greater between signal circuit terminal 7 and ground. ⇒ If less that 8 V 3.1. Test the appropriate circuit for a short to ground: E13LA Front Headlamp - Left = Circuit 6568 E13RA Front Headlamp - Right = Circuit 7545 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 3.2. Test the appropriate circuit for an open/high resistance: E13LA Front Headlamp - Left = Circuit 6568 E13RA Front Headlamp - Right = Circuit 7545 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 3.3. Replace the K219 Lighting Control Module. ⇓ If 8 V or greater
  4. Verify a test lamp does not illuminate between signal circuit terminal 7 and ground. ⇒ If the test lamp illuminates 4.1. Test the appropriate circuit for a short to voltage: E13LA Front Headlamp - Left = Circuit 6568 E13RA Front Headlamp - Right = Circuit 7545 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 4.2. Replace the K219 Lighting Control Module. ⇓ If the test lamp does not illuminate
  5. Replace the appropriate lamp assembly for an internal fault. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup