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Tahoe / Yukon Service Manual

DTC B10A9 or B1BB5

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 B10A9 Left Rear Trailer Stop/Turn Lamp Control DTC B1BB5 Right Rear Trailer Stop/Turn Lamp 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
318 Control B10A9 11 B10A9 13 B10A9 12 —
319 Control B1BB5 11 B1BB5 13 B1BB5 12 —
1. Trailer Lamps Malfunction

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

Control Function Description
Left Trailer Turn Signal/Stop Lamp Command This control function will control the left trailer turn signal/stop lamp at the X88B Tow Vehicle Electrical Receptacle On/Off.
Right Trailer Turn Signal/Stop Lamp Command This control function will control the right trailer turn signal/stop 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 circuit(s). With the relay coil energized, the relay contacts close and allow voltage to flow through the relay illuminating the appropriate lamps on the attached trailer. For stop lamp operation, the lighting control module will control the both trailer stop/turn signal lamp relays ON anytime the stop lamp are commanded ON. For turn signal lamp operation, the lighting control module will control the appropriate trailer stop/turn signal lamp relay in an ON/OFF duty cycle when the turn signal lamps are commanded ON. 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. Stop lamps or turn signal lamps ON. Conditions for Setting the DTC DTC B10A9 11 The K219 lighting control module detects a short to ground on control circuit 318. DTC B10A9 12 The K219 lighting control module detects a short to voltage on control circuit 318. DTC B10A9 13 The K219 lighting control module detects an open/high resistance on control circuit 318. DTC B1BB5 11 The K219 lighting control module detects a short to ground on control circuit 319. DTC B1BB5 12 The K219 lighting control module detects a short to voltage on control circuit 319. DTC B1BB5 13 The K219 lighting control module detects an open/high resistance on control circuit 319. Actions Taken When the DTC Sets The appropriate trailer stop/turn signal 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 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 appropriate trailer fuse and ground, ignition ON/vehicle in service mode: DTC B10A9 = Fuse F73UA DTC B1BB5 = Fuse F81UA
  1. Verify the test lamp turns ON and OFF when commanding the appropriate trailer lamp ON and OFF with a scan tool: Left Trailer Turn Signal/Stop Lamp Command Right Trailer Turn Signal/Stop Lamp Command ⇒ 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 appropriate trailer fuse and ground: DTC B10A9 = Fuse F73UA DTC B1BB5 = Fuse F81UA
  1. Verify the test lamp turns ON and OFF when commanding the appropriate trailer lamp ON and OFF with a scan tool: DTC B10A9 = Left Trailer Turn Signal/Stop Lamp Command DTC B1BB5 = Right Trailer Turn Signal/Stop Lamp Command ⇒ 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 circuit or ground connection. ⇓ If an open/high resistance is not found. 3.2. Test the appropriate control circuit for a short to ground: DTC B10A9 = Circuit 318 DTC B1BB5 = Circuit 319 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found. 3.3. Test the appropriate control circuit for an open/high resistance: DTC B10A9 = Circuit 318 DTC B1BB5 = Circuit 319 ⇒ 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 the appropriate control circuit for a short to voltage: DTC B10A9 = Circuit 318 DTC B1BB5 = Circuit 319 ⇒ 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