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Tahoe / Yukon Service Manual

DTC B19A3 or B19A4

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 B19A3 Left Daytime Running Lamp Control Circuit DTC B19A4 Right Daytime Running Lamp Control Circuit Diagnostic Fault Information

Circuit Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
7538 Control B19A3 11 1 1 —
7539 Control B19A4 11 1 1 —
150 Ground — 1 — —
250 Ground — 1 — —
1. Daytime Running Lamps Malfunction

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

Control Function Description
Left Daytime Running Lamps This control function will control the left daytime running lamp ON/OFF
Right Daytime Running Lamps This control function will control the right daytime running lamp ON/OFF

Circuit/System Description The B10D Sun Load and Ambient Light and Security Indicator Sensor is used to monitor outside lighting conditions. The ambient light sensor provides a voltage signal that will vary between 0.2 and 4.9 volts depending on outside lighting conditions. The K9 Body Control Module (BCM) monitors the ambient light sensor signal circuit to determine if outside lighting conditions are correct for either daytime running lamps (DRL) or automatic lamp control when the headlamp switch is in the AUTO position. In daylight conditions, the BCM will send a message to the K219  Lighting Control Module to request the DRLs ON. The Lighting Control Module responds by applying pulse width modulated (PWM) voltage to the left and right DRL circuits illuminating the DRLs. During low light conditions, the BCM will send a message to the Lighting Control Module to request the low beam headlamps ON. The Lighting Control Module responds by applying voltage to the low beam circuits illuminating the low beams. Diagnostic Aids Daytime running lamps (DRL) have different intensities based on ambient light conditions. The DRLs will be fully illuminated under bright ambient light conditions and have less intensity under dark ambient light conditions. Conditions for Running the DTC Battery voltage must be between 9-16 V. Headlamp switch in AUTO position. Conditions for Setting the DTC DTC B19A3 11 The Lighting Control Module detects a short to ground on circuit 7538. DTC B19A4 11 The Lighting Control Module detects a short to ground on circuit 7539. Actions Taken When the DTC Sets DTC B19A3 The left daytime running lamp will be inoperative. DTC B19A4 The right daytime running 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 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 B19A3

  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 5 and ground, ignition ON.
  4. Verify the test lamp turns ON and OFF when commanding the Left Daytime Running Lamps ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 7538 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 7538 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 7538 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. Test or replace the E13LA Front Headlamp – Left. DTC B19A4
  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 5 and ground, ignition ON.
  9. Verify the test lamp turns ON and OFF when commanding the Right Daytime Running Lamps ON and OFF with a scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 7539 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 7539 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 7539 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. Test or 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