Skip to content
Tahoe / Yukon Service Manual

DTC B1048

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 B1048 Interior Lamp Control 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
157 Control B1048 11 1 1 —
1850 Ground — 1 — —
1. Courtesy Lamps Malfunction

Circuit/System Description When any door is opened, the jam switch contacts close and the body control module (BCM) receives a door-ajar input. If the BCM receives a door lock or unlock input or a rear hatch open input, the BCM will provide pulse width modulated (PWM) voltage to control circuit 157. In the event that any of these courtesy lamps were to remain illuminated for more than 10 min with the ignition switch in the OFF position, the BCM will deactivate the courtesy lamp control circuit to prevent total battery discharge. Conditions for Running the DTC Battery voltage must be between 9-16 V. Conditions for Setting the DTC The BCM detects a short to ground in the dome/courtesy lamps control circuit 157. Actions Taken When the DTC Sets The BCM will disable control circuit 157. 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 Interior Lights Schematics Connector End View Reference Master Electrical Component List Description and Operation Interior 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/vehicle off, disconnect the X2 connector at the K9 Body Control Module.
  2. Connect a 3 A fused jumper wire between control circuit terminal 1 and B+.
  3. Verify the accent lamps turn on and off when connecting and disconnecting the jumper wire: E8VA Front Floor Courtesy Lamp - Left E8VC Front Floor Courtesy Lamp - Right ⇒ If an accent lamp is always off and the jumper fuse is OK. 3.1. Test the appropriate ground circuit for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit or ground connection. ⇓ If an open/high resistance is not found. 3.2. Test circuit 157 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. 3.3. Replace the appropriate accent lamp. ⇒ If an accent lamp is always off and the jumper fuse is open 3.1. Test circuit 157 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. 3.2. Replace the appropriate accent lamp. ⇒ If an accent lamp is always on 3.1. Test circuit 157 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. 3.2. Replace the appropriate accent lamp. ⇓ If the accent lamps turn on and off
  4. Replace the K9 Body Control Module. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Lighting Component Replacement Reference Control Module References for BCM replacement, programming, and setup