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Tahoe / Yukon Service Manual

DTC B1996 or B1997

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 B1996 Left Headlamp Low Beam Control Circuit DTC B1997 Right Headlamp Low 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
712 Control B1996 11 1 1 —
312 Control B1997 11 1 1 —
2750 Ground — 1 — —
650 Ground — 1 — —
1. Headlamps Malfunction

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

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

Circuit/System Description The headlamp low beams are controlled through the S30 Headlamp Switch. With the headlamp switch is in the ON position, the headlamp ON signal circuit is grounded through the headlamp switch. The K9 Body Control Module (BCM) responds by sending a serial data message to the K219 Lighting Control Module to command the low beam headlamps ON. The Lighting Control Module responds by applying pulse width modulated (PWM) voltage to the left and right low beam headlamp control circuits illuminating the low beam headlamps. Conditions for Running the DTC Battery voltage must be between 9-16 V Battery voltage must be between 9 16 V. Low beam headlamps ON. Conditions for Setting the DTC B1996 11 The Lighting Control Module detects a short to ground on circuit 712. B1997 11 The Lighting Control Module detects a short to ground on circuit 312. Actions Taken When the DTC Sets When DTC B1996 sets, the left low beam headlamp will be inoperative. When DTC B1997 sets, the right low 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 B1996

  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 3 and ground, ignition ON.
  4. Verify the test lamp turns ON and OFF when commanding the Left Headlamp Low Beam ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 712 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 712 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 712 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 B1997
  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 3 and ground, ignition ON.
  9. Verify the test lamp turns ON and OFF when commanding the Right Headlamp Low Beam ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 312 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 312 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 312 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