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Tahoe / Yukon Service Manual

DTC B2A87-B2A8A (LM2)

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 B2A87 00 Front Faceplate Temperature Control Front 1 Left Circuit High DTC B2A88 00 Front Faceplate Temperature Control Front 1 Left Circuit Low DTC B2A8A 00 Front Faceplate Temperature Control Front 1 Left Performance Circuit/System Description The A26 Heater and Air Conditioning User Interface Control - Front communicates with the K9 Body Control Module via serial data. When the BCM receives an abnormal switch signal voltage message from the user interface control, the BCM sets the DTC. Conditions for Running the DTC B2A87, B2A88 The BCM is awake and communicating The user interface control is awake and communicating System voltage = 9 – 16 V DTCs U0164, U0424 are not set B2A8A The BCM is awake and communicating The user interface control is awake and communicating System voltage = 9 – 16 V DTCs B2A87, B2A88, U0164, or U0424 are not set Conditions for Setting the DTC B2A87 The BCM receives a switch signal voltage message too high out of the expected range B2A88 The BCM receives a switch signal voltage message too low out of the expected range B2A8A The BCM receives a valid switch signal voltage message for greater than a calibrated time (approximately 90 seconds). Action Taken when the DTC Sets The BCM does not respond to the switch signal message. e C does ot espo d to t e s tc s g a essage DTC Type B Conditions for Clearing the DTC DTC Type B Diagnostic Aids This DTC may be stored as a history DTC without affecting the operation of the user interface control. If stored only as a history DTC and not retrieved as a current DTC, do not replace the user interface control. If this DTC is retrieved as both a current and history DTC, replace the user interface control. DTC B2A8A may be caused by a stuck or sticking switch. Reference Information Schematic Reference HVAC Schematics Connector End View Reference Master Electrical Component List Description and Operation Automatic HVAC Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Ignition ON/ Vehicle in Service Mode.
  2. Verify DTC B2A87–B2A8A is not set. ⇒ If any of the DTCs are set Replace the A26 Heater and Air Conditioning User Interface Controls– Front. ⇓ If none of the DTCs are set
  3. A fault is not currently present and may be an intermittent condition. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. HVAC Component Replacement Reference Control Module References for control module replacement, programming and setup