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Tahoe / Yukon Service Manual

Headlamps 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 Circuit Function Short to Ground Open/Hig Resistance h Short to Voltage Signal Performan ce
712 Control B1996 11 1 1 —
312 Control B1997 11 1 1 —
711 Control B1995 11 1 1 —
311 Control B1994 11 1 1 —
13 Signal 2 2 2 —
103 Signal 2 2 2 —
306 Signal 2 2 2 —
524 Signal 2 2 3 —
307 Signal 3 3 3 —
278 Signal B108E 00 B108E 00 B108E 00 4
407 Low Reference 4 B108E 00 4 —
150 Ground — B1996 13, B1995 13 — —
250 Ground — B1997 13, B1994 13 — —
1850 Ground — 2, 3 — —
1. Headlamps Malfunction 2. Headlamp Switch Malfunction 3. Turn Signal Switch Malfunction

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

Data Parameter Description
Ambient Light Intensity This data parameter will show the status of the Ambient Light Sensor as a high LX value under bright ambient light conditions and a low LX value under dark ambient light conditions.
Headlamp Switch Signal This data parameter will show the status of the headlamp switch as AUTO, OFF, PARK, or ON depending on headlamp switch status.
Flash To Pass This data parameter will show the status of the flash to pass switch as Active/Inactive as the turn signal switch is moved to the flash to pass position and back.
Left/Right High Beam Status This data parameter will show the status of each high beam headlamp as Active/Inactive when the high beams are being commanded ON/OFF with the turn signal switch.

K219 Lighting Control Module – Control Functions – Exterior Lighting

Control Function Description
Left Low Beam Command This control function will control the left low beam headlamp On/Off.
Right Low Beam Command This control function will control the right low beam headlamp On/Off.
Left High Beam This control function will control the left high beam headlamp On/Off.
Right High Beam This control function will control the right high beam headlamp On/Off.

Circuit/System Description Low Beams For headlamp operation, the K9 Body Control Module (BCM) monitors three signal circuits from the S30 Headlamp Switch. When the headlamp switch is in the AUTO position, the three signal circuits are unaffected (open) and the BCM relies on the B10D Sun Load and Ambient Light and Security Indicator Sensor input to turn the headlamps and daytime running lamps ON and OFF. When the headlamp switch is placed in the OFF position, the headlamps OFF signal circuit 306 is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the headlamp switch in the PARK LAMPS position, the park lamps ON signal circuit 13 is grounded, indicating that the park lamps have been requested. When the headlamp switch is in the HEADLAMP position, both the park lamps ON signal circuit 13 and the headlamps ON signal circuit 103 are grounded. The BCM responds to the low beam request by sending a serial data message to the K219 Lighting Control Module. The Lighting Control Module responds by applying pulse width modulated voltage (PWM) to both headlamp low beam control circuits, illuminating the low beam headlamps. High Beams The high beam and flash to pass (FTP) functions are contained within the S78 Turn Signal Switch. The K9 Body Control Module (BCM) provides the turn signal switch with two signal circuits, the high beam signal circuit 524 and the FTP signal circuit 307. When the low beam headlamps are ON, and the turn signal switch is placed in either the high beam position or FTP position, ground is applied to the BCM through the high beam or FTP signal circuit. The BCM responds to the high beam request by sending a serial data message to the K219 Lighting Control Module. The Lighting Control Module responds by applying pulse width modulated voltage (PWM) to both headlamp high beam control circuits, illuminating the high beam headlamps. Automatic Headlamp Control The B10D Sun Load and Ambient Light and Security Indicator Sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 volts depending on outside lighting conditions. The K9 Body Control Module (BCM) provides signal circuit 278 and low reference circuit 407 to the ambient light sensor. The BCM monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lamps or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions the BCM will request the daytime running lamps ON through a serial data message to the K219 Lighting Control Module. During low light conditions the BCM will request the low beam headlamps ON through a serial data message to the lighting control module. Reference Information Schematic Reference Headlights/Daytime Running Lights (DRL) 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.
  2. Verify there are no related DTCs set. ⇒ If related DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no related DTCs are set
  3. Verify the scan tool Headlamp Switch Signal data parameter changes between all modes when placing the headlamp switch in each position. ⇒ If the parameter does not change properly Refer to Circuit/System Testing – Headlamp Switch Malfunction. ⇓ If the parameter changes properly
  4. Verify the Flash To Pass data parameter changes between Active/Inactive when placing the turn signal switch in the flash to pass position. ⇒ If the parameter does not change Refer to Circuit/System Testing – Turn Signal Switch Malfunction. ⇓ If the parameter changes
  5. Verify the Ambient Light Intensity data parameter value changes appropriately: LX value increases with an incandescent light shined on the B10D Sun Load and Ambient Light and Security Indicator Sensor to simulate bright conditions. LX value decreases with a towel covering the B10D Sun Load and Ambient Light and Security Indicator Sensor to simulate dark conditions. ⇒ If the value does not change Refer to Circuit/System Testing – Ambient Light Sensor Malfunction ⇓ If the value changes
  6. Low beams ON, verify the Left/Right High Beam Status data parameter changes between Active/Inactive when placing the turn signal switch in and out the high beam position. ⇒ If the parameter does not change Refer to Circuit/System Testing – Turn Signal Switch Malfunction. ⇓ If the parameter changes
  7. Verify the left and right low beam headlamps turn ON and OFF when commanding the Left and Right Low Beams ON and OFF with a scan tool. ⇒ If the low beam headlamps do not turn ON and OFF Refer to Circuit/System Testing – Headlamps Malfunction – Low Beam. ⇓ If the low beam headlamps turn ON and OFF
  8. Verify the left and right high beams turn ON and OFF when commanding the Left and Right High Beams ON and OFF with a scan tool. ⇒ If the high beams do not turn ON and OFF Refer to Circuit/System Testing – Headlamps Malfunction – High Beam. ⇓ If the high beams turn ON and OFF
  9. A fault is not currently present and may be an intermittent condition. Circuit/System Testing Headlamp Switch Malfunction
  10. Ignition OFF, disconnect the connector at the S30 Headlamp Switch.
  11. Verify a test lamp illuminates between ground circuit terminal 8 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
  12. Ignition on, test for 7–8 V between both signal circuit terminals and ground: Headlamps on = Terminal 1 Headlamps off = Terminal 3 ⇒ If less than 7 V 3.1. Test the appropriate circuit for a short to ground: Headlamps on = Circuit 103 Headlamps off = Circuit 306 ⇒ 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: Headlamps on = Circuit 103 Headlamps off = Circuit 306 ⇒ 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 7 V 3.1. Test the appropriate circuit for a short to voltage: Headlamps on = Circuit 103 Headlamps off = Circuit 306 ⇒ 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 between 7–8 V
  13. Replace the S30 Headlamp Switch. Turn Signal Switch Malfunction
  14. Ignition/vehicle OFF, disconnect the S78 Turn Signal Switch.
  15. 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 the ground circuit or ground connection. ⇓ If the test lamp illuminates
  16. Ignition on, test for 7–8 V between the appropriate signal circuit terminal and ground: Flash to pass = Terminal 1 High beams = Terminal 3 ⇒ If less than 7 V 3.1. Test the appropriate circuit for a short to ground: Flash to pass = Circuit 307 High beams = Circuit 524 ⇒ 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: Flash to pass = Circuit 307 High beams = Circuit 524 ⇒ 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 7 V 3.1. Test the appropriate circuit for a short to voltage: Flash to pass = Circuit 307 High beams = Circuit 524 ⇒ 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 between 7–8 V
  17. Replace the S78 Turn Signal Switch. Ambient Light Sensor Malfunction
  18. Ignition OFF, disconnect the connector at the B10D Sun Load and Ambient Light and Security Indicator Sensor, ignition on.
  19. Verify a test lamp illuminates between low reference terminal 6 and B+. ⇒ If the test lamp does not illuminate 2.1. Test circuit 407 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found. 2.2. Replace the K9 Body Control Module. ⇓ If the test lamp illuminates
  20. Test for 4.8 V – 5.2 V between signal circuit terminal 3 and ground. ⇒ If less than 4.8 V 3.1. Test circuit 278 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 3.2. Test circuit 278 for an open/high resistance. ⇒ 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 5.2 V 3.1. Test circuit 278 for a short to voltage. ⇒ 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 between 4.8 V – 5.2 V
  21. Replace the B10D Sun Load and Ambient Light and Security Indicator Sensor. Headlamps Malfunction – Low Beam
  22. Ignition OFF, disconnect the connector at the appropriate component: E13LA Front Headlamp – Left = X110 E13RA Front Headlamp – Right = X120
  23. 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
  24. Ignition on/vehicle in service mode, verify a test light illuminates between B+ circuit terminal 2 and ground ⇒ If the test light does not illuminate and the circuit fuse is OK 3.1. Test the appropriate circuit for an open/high resistance: E13LA Front Headlamp – Left = Circuit 640 E13RA Front Headlamp – Right = Circuit 740 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 3.2. Verify there is voltage at the fuse. ⇒ If the test light does not illuminate and the circuit fuse is open 3.1. Test the appropriate circuit for a short to ground: E13LA Front Headlamp – Left = Circuit 640 E13RA Front Headlamp – Right = Circuit 740 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 3.2. Replace the appropriate E13 Headlamp Assembly. ⇓ If the test light illuminates
  25. Connect a test lamp between control circuit terminal 3 and ground.
  26. Verify the test lamp turns on and off when commanding the appropriate Low Beams on and off with a scan tool. ⇒ If the test lamp is always OFF 5.1. Test the appropriate circuit for a short to ground: E13LA Front Headlamp – Left = Circuit 712 E13RA Front Headlamp – Right = Circuit 312 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 5.2. Test the appropriate circuit for an open/high resistance: E13LA Front Headlamp – Left = Circuit 712 E13RA Front Headlamp – Right = Circuit 312 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 5.3. Replace the K219 Lighting Control Module. ⇒ If the test lamp is always ON 5.1. Test the appropriate circuit for a short to voltage: E13LA Front Headlamp – Left = Circuit 712 E13RA Front Headlamp – Right = Circuit 312 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 5.2. Replace the K219 Lighting Control Module. ⇓ If the test lamp turns ON and OFF
  27. Replace the appropriate E13 Headlamp Assembly. Headlamps Malfunction – High Beam
  28. Ignition OFF, disconnect the connector at the appropriate component: E13LA Front Headlamp – Left = X110 E13RA Front Headlamp – Right = X120
  29. 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
  30. Ignition on/vehicle in service mode, verify a test light illuminates between B+ circuit terminal 2 and ground ⇒ If the test light does not illuminate and the circuit fuse is OK 3.1. Test the appropriate circuit for an open/high resistance: E13LA Front Headlamp – Left = Circuit 640 E13RA Front Headlamp – Right = Circuit 740 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 3.2. Verify there is voltage at the fuse. ⇒ If the test light does not illuminate and the circuit fuse is open 3.1. Test the appropriate circuit for a short to ground: E13LA Front Headlamp – Left = Circuit 640 E13RA Front Headlamp – Right = Circuit 740 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 3.2. Replace the appropriate E13 Headlamp Assembly. ⇓ If the test light illuminates
  31. Connect a test lamp between control circuit terminal 4 and ground.
  32. Verify the test lamp turns on and off when commanding the appropriate High Beams on and off with a scan tool. ⇒ If the test lamp is always OFF 5.1. Test the appropriate circuit for a short to ground: E13LA Front Headlamp – Left = Circuit 711 E13RA Front Headlamp – Right = Circuit 311 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 5.2. Test the appropriate circuit for an open/high resistance: E13LA Front Headlamp – Left = Circuit 711 E13RA Front Headlamp – Right = Circuit 311 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 5.3. Replace the K219 Lighting Control Module. ⇒ If the test lamp is always ON 5.1. Test the appropriate circuit for a short to voltage: E13LA Front Headlamp – Left = Circuit 711 E13RA Front Headlamp – Right = Circuit 311 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found. 5.2. Replace the K219 Lighting Control Module. ⇓ If the test lamp turns ON and OFF
  33. Replace the appropriate E13 Headlamp Assembly. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup