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Tahoe / Yukon Service Manual

DTC B1B0C or B1B0D

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 Descriptor DTC B1B0C Left Running Board Step Courtesy Lamp Control DTC B1B0D Right Running Board Step Courtesy Lamp Control Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Left Running Board Courtesy Lamp Control B1B0C 11 B1B0C 13 B1B0C 12 —
Right Running Board Courtesy Lamp Control B1B0D 11 B1B0D 13 B1B0D 12 —
Ground — 1 1 —
1. Courtesy lamp inoperative.

Circuit/System Description The assist step control module supplies power to the left and right control circuit of the left and right assist step courtesy lamp. When the keyless entry transmitter is operated to either the lock or unlock functions, the LED lighting located under each outside rearview mirror, exterior door handles, and both running board steps are commanded ON for approach lighting. Conditions for Running the DTC The ignition is ON. Ignition voltage is between 9–16V. Ambient light sensor must be covered. Conditions for Setting the DTC B1B0C 11, B1B0D 11 The K4 Assist Step Control Module detects a short to ground on the courtesy lamp control circuit. B1B0C 12, B1B0D 12 The K4 Assist Step Control Module detects a short to voltage on the courtesy lamp control circuit. B1B0C 13, B1B0D 13 The K4 Assist Step Control Module detects an open/high resistance on the courtesy lamp control circuit. Action Taken When the DTC Sets Courtesy lamps inoperative. Conditions for Clearing the DTC The DTC becomes history when the assist step control module no longer detects the condition that set the DTC. Reference Information Schematic Reference Step/Running Board Schematics Exterior Lights Schematics Connector End View Reference Master Electrical Component List Description and Operation Running Board Description 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 Verification

  1. Ignition ON.
  2. Verify the scan tool Left Assist Step Courtesy Lamp parameter changes between Active and Inactive while commanding the Left Assist Step Courtesy Lamp ON and OFF with the scan tool. ⇒ If the parameter does not change Refer to Circuit/System Testing. ⇓ If the parameter changes
  3. Verify the scan tool Right Assist Step Courtesy Lamp parameter changes between Active and Inactive while commanding the Right Assist Step Courtesy Lamp ON and OFF with the scan tool. ⇒ If the parameter does not change Refer to Circuit/System Testing. ⇓ If the parameter changes
  4. A fault is currently not present and may be an intermittent condition Circuit/System Testing
  5. Ignition OFF and all vehicle systems OFF. It may take up to 2 min for all vehicle systems to power down. Disconnect the appropriate harness connector: E8ZL Assist Step Lamp – Left E8ZR Assist Step Lamp – RIght
  6. Verify a test lamp illuminates between the appropriate ground circuit terminal 1 and B+ ⇒ If the test lamp does not illuminate 2.1. Ignition OFF. 2.2. Test for less than 2 Ω in the ground circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, replace the K4 Assist Step Control Module. ⇓ If the test lamp illuminates
  7. Connect a test lamp between the appropriate control circuit terminal 2 and ground. Ignition ON/vehicle in service mode.
  8. Verify the test lamp turns ON and OFF while commanding the Assist Step Courtesy Lamp ON and OFF with the scan tool. ⇒ If the test lamp is always OFF 4.1. Ignition OFF, remove the test lamp, disconnect the X3 harness connector at the K4 Assist Step Control Module. 4.2. Test for infinite resistance between the control circuit terminal and ground. ⇒ If less than infinite resistance, repair the short to ground on the circuit. ⇓ If infinite resistance 4.3. Test for less than 2 Ω in the control circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω replace the K4 Assist Step Control Module. ⇓ If the test lamp is always ON 4.1. Ignition OFF, remove the test lamp, disconnect the X3 harness connector at the K4 Assist Step Control Module, ignition ON. 4.2. Test for less than 1 V between the signal circuit and ground. ⇒ If 1 V or greater, repair the short to voltage on the circuit. ⇒ If less than 1 V, replace the K4 Assist Step Control Module. ⇓ If the test lamp turns ON and OFF Replace the appropriate component: E8ZL Assist Step Lamp – Left E8ZL Assist Step Lamp – Right Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Assist Step Lamp Replacement Control Module References for control module replacement, programming and setup.