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Tahoe / Yukon Service Manual

DTC B1994 or B1995

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 B1994 Right Headlamp High Beam Control Circuit DTC B1995 Left Headlamp High Beam 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
311 Control B1994 11 1 1 —
711 Control B1995 11 1 1 —
250 Ground — 1 — —
150 Ground — 1 — —
1. Headlamps Malfunction

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

Control Function Description
Left High Beam This control function will control the left high beam ON/OFF
Right High Beam This control function will control the right high beam ON/OFF

Circuit/System Description The high beam and flash to pass functions are contained within the turn signal switch. The K9  Body Control Module (BCM) provides the turn signal switch with two signal circuits, the high beam signal circuit and the flash to pass signal circuit. When the low beam headlamps are ON and the turn signal switch is placed in the high beam position, ground is applied to the BCM through the high beam signal circuit. The BCM responds to the high beam request by sending a serial data message to the K219 Lighting Control Module to command the high beam headlamps on. The Lighting Control Module responds by applying pulse width modulated (PWM) voltage to the left high beam control circuit 711 and right high beam control circuit 311 which illuminates the high beam lamps. Conditions for Running the DTC Battery voltage must be between 9-16 V. High beam headlamps ON. Conditions for Setting the DTC DTC B1994 11 The Lighting Control Module detects a short to ground on circuit 311. DTC B1995 11 The Lighting Control Module detects a short to ground on circuit 711. Actions Taken When the DTC Sets When DTC B1994 sets, the right high beam headlamp will be inoperative. When DTC B1995 sets, the left high beam headlamp will be inoperative. 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 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 Testing DTC B1994

  1. Ignition OFF, exterior lamps OFF, disconnect the X120 connector at the 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 circuit 250 or ground connection. ⇓ If the test lamp illuminates
  3. Connect a test lamp between the control circuit terminal 4 and ground, ignition ON.
  4. Verify the test lamp turns ON and OFF when commanding the Right High Beam ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 311 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 311 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 311 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 E13RA Front Headlamp – Right. DTC B1995
  6. Ignition OFF, exterior lamps OFF, disconnect the X110 connector at the E13LA Front Headlamp – Left.
  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 150 or ground connection. ⇓ If the test lamp illuminates
  8. Connect a test lamp between the control circuit terminal 4 and ground, ignition ON.
  9. Verify the test lamp turns ON and OFF when commanding the Left High Beam ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 711 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 711 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 711 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 E13LA Front Headlamp – Left. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup