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Tahoe / Yukon Service Manual

DTC B1998 or B1999

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 B1998 Left Front Turn Signal Lamp Control Circuit DTC B1999 Right Front Turn Signal Lamp Control Circuit Refer to Symptom Byte List for symptom byte information. Diagnostic Fault Information

Circuit Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
1314 Control B1998 11 1 1 —
1315 Control B1999 11 1 1 —
2750 Ground — 1 — —
650 Ground — 1 — —
1. Turn Signal Malfunction

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

Control Function Description
Left Front Turn Signal Lamp This control function will control the left front turn signal ON/OFF
Right Front Turn Signal Lamp This control function will control the right front turn signal ON/OFF

Circuit/System Description Ground is applied at all times to the turn signal switch. The turn signal lamps may only be activated with the ignition on/vehicle in service mode. When the turn signal switch is placed in either the turn right or turn left position, ground is applied to the K9 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 sending a serial data message to the K219 Lighting Control Module to command the appropriate turn signals ON and OFF. The Lighting Control Module responds by applying a pulsating voltage to the front, rear, and mirror turn signal lamps through their 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. Conditions for Running the DTC Battery voltage must be between 9-16 V. Conditions for Setting the DTC DTC B1998 11 The Lighting Control Module detects a short to ground on circuit 1314. DTC B1999 11 The Lighting Control Module detects a short to ground on circuit 1315. Actions Taken When the DTC Sets DTC B1998 The left front turn signal is inoperative. The “Check Left Front Turn Lamp” message is displayed on the driver information center display. The left turn signal indicator on the instrument cluster flashes rapidly DTC B1999 The right front turn signal is inoperative. The “Check Right Front Turn Lamp” message is displayed on the driver information center display. The right turn signal indicator on the instrument cluster flashes rapidly Conditions for Clearing the DTC The condition responsible for setting the DTC no longer exists. A history DTC will clear once 40 consecutive malfunction-free ignition cycles have occurred. 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 Control Module References for scan tool information Circuit/System Testing DTC B1998

  1. Ignition OFF, exterior lamps OFF, disconnect the X110 connector at the E13LA Front Headlamp – Left.
  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 circuit 150 or ground connection. ⇓ If the test lamp illuminates
  3. Connect a test lamp between the control circuit terminal 6 and ground, ignition ON.
  4. Verify the test lamp turns ON and OFF when commanding the Left Front Turn Signal ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 1314 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 4.2. Test circuit 1314 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 4.3. Replace the K219 Lighting Control Module. ⇒ If the test lamp is always ON 4.1. Test circuit 1314 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 4.2. Replace the K219 Lighting Control Module. ⇓ If the test lamp turns ON and OFF
  5. Replace the E13LA Front Headlamp – Left. DTC B1999
  6. Ignition OFF, exterior lamps OFF, disconnect the X120 connector at the E13RA Front Headlamp – Right.
  7. 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 circuit 250 or ground connection. ⇓ If the test lamp illuminates
  8. Connect a test lamp between the control circuit terminal 6 and ground, ignition ON.
  9. Verify the test lamp turns ON and OFF when commanding the Right Front Turn Signal ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 1315 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 4.2. Test circuit 1315 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 4.3. Replace the K219 Lighting Control Module. ⇒ If the test lamp is always ON 4.1. Test circuit 1315 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 4.2. Replace the K219 Lighting Control Module. ⇓ If the test lamp turns ON and OFF
  10. Replace the E13RA Front Headlamp – Right. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup