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Tahoe / Yukon Service Manual

DTC B198F or B1990

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 B198F Right Rear Stop Lamp Control Circuit DTC B1990 Left Rear Stop Lamp Control Circuit Symptom Byte List Diagnostic Fault Information

Circuit Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
7541 Control B198F 11 1 1 —
7542 Control B1990 11 1 1 —
2050 Ground — 1 — —
1950 Ground — 1 — —
1. Stop Lamps Malfunction

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

Control Function Description
Left Stop Lamp This control function will control the left stop lamp ON/OFF
Right Stop Lamp This control function will control the right stop lamp ON/OFF

Circuit/System Description The B22 Brake Pedal Position Sensor is used to sense the action of the driver application of the brake pedal. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the K9 Body Control Module (BCM) sends a serial data message to the K219 Lighting Control Module to illuminate the stop lamps. The Lighting Control Module responds by applying voltage to the left stop lamp control circuit 7542 and the right stop lamp control circuit 7541 as well as the center high mounted stop lamp (CHMSL) control circuit 820 illuminating the left and right stop lamps and the CHMSL. Conditions for Running the DTC Battery voltage must be between 9-16 V. Brake pedal applied. Conditions for Setting the DTC DTC B198F 11 The Lighting Control Module detects a short to ground on circuit 7541. DTC B1990 11 The Lighting Control Module detects a short to ground on circuit 7542. Actions Taken When the DTC Sets DTC B198F The left rear stop lamp will be inoperative. DTC B1990 The right rear stop lamp 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 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 Scan Tool Reference Control Module References for scan tool information Circuit/System Testing

  1. Ignition OFF, disconnect the appropriate component: DTC B198F = E42R Tail Lamp Assembly – Right DTC B1990 = E42L Tail Lamp Assembly – 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 the ground circuit or ground connection. ⇓ If the test lamp illuminates
  3. Connect a test lamp between control circuit terminal 2 and ground, ignition on.
  4. Verify the test lamp turns on and off when commanding the appropriate Stop Lamp on and off with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test the appropriate circuit for a short to ground: E42R Tail Lamp Assembly – Right = Circuit 7541 E42L Tail Lamp Assembly – Left = Circuit 7542 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Test the appropriate circuit for an open/high resistance: E42R Tail Lamp Assembly – Right = Circuit 7541 E42L Tail Lamp Assembly – Left = Circuit 7542 ⇒ 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 the appropriate circuit for a short to voltage: E42R Tail Lamp Assembly – Right = Circuit 7541 E42L Tail Lamp Assembly – Left = Circuit 7542 ⇒ 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 appropriate stop lamp. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup