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Tahoe / Yukon Service Manual

DTC B100C

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. DTC Descriptors DTC B100C Backup Lamp Relay Control Refer to Symptom Byte List for symptom byte information. Diagnostic Fault Information

Circuit Circuit Descriptio Short to n Ground Open/High Resistance Short to Voltage Signal Performan
38 Control B100C 11 B100C 13 B100C 12 —
1. Trailer Lamps Malfunction

Scan Tool Functions K219  Lighting Control Module – Control Functions – Exterior Lighting

Control Function Description
Trailer Backup Lamps This control function will control the trailer backup lamp at the X88B Tow Vehicle Electrical Receptacle On/Off.

Circuit/System Description The K219 Lighting Control Module receives serial data messages from the K9 Body Control Module (BCM) indicating what lamps have been activated on the vehicle. The lighting control module responds by applying voltage to the appropriate relay control circuits. With the relay coil energized, the relay contacts close and allow voltage to flow through the relay illuminating the appropriate lamps on the trailer. Diagnostic Aids Trailer lighting is controlled through non-serviceable printed circuit board (PCB) relays. A defective relay will require complete fuse block replacement. Conditions for Running the DTC Battery voltage must be between 9–16 V. Transmission in reverse. Conditions for Setting the DTC DTC B100C 11 The K219 lighting control module detects a short to ground on control circuit 38. DTC B100C 12 The K219 lighting control module detects a short to voltage on control circuit 38. DTC B100C 13 The K219 lighting control module detects an open/high resistance on control circuit 38. Actions Taken When the DTC Sets The trailer backup lamps will be inoperative. Conditions for Clearing the DTC The condition responsible for setting the DTC no longer exists. A history DTC will clear once 50 consecutive malfunction-free ignition cycles have occurred. Reference Information Schematic Reference Trailering Systems Schematics Exterior Lights Schematics Connector End View Reference Master Electrical Component List Description and Operation Trailering 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. Connect a test lamp between the trailer backup lamp Fuse F55UA and ground, ignition ON/vehicle in service mode.
  1. Verify the test lamp turns ON and OFF when commanding the Trailer Backup Lamp ON and OFF with a scan tool. ⇒ If the test lamp does not turn ON and OFF Refer to Circuit/System Testing ⇓ If the test lamp turns ON and OFF
  2. A fault is not currently present and may be an intermittent condition. Circuit/System Testing
  3. Ignition ON/vehicle in service mode, exterior lamps OFF.
  4. Connect a test lamp between the trailer backup lamp Fuse F55UA and ground.
  1. Verify the test lamp turns ON and OFF when commanding the Trailer Backup Lamps ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 3.1. Test the ground circuit at the X50A Engine Wiring Harness Junction Block for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the ground circuit or ground connection. ⇓ If an open/high resistance is not found. 3.2. Test control circuit 38 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. 3.3. Test control circuit 38 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. 3.4. Replace the X50A Engine Wiring Harness Junction Block. ⇒ If the test lamp is always ON 3.1. Test control circuit 38 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 X50A Engine Wiring Harness Junction Block. ⇓ If the test lamp turns ON and OFF
  2. Replace the K219 Lighting Control Module. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Control Module References for trailer lamp control module replacement, programming, and setup