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Tahoe / Yukon Service Manual

DTC B2A6B-B2A6E (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 B2A6B 00 Front Faceplate Power Front Control Circuit High DTC B2A6C 00 Front Faceplate Power Front Control Circuit Low DTC B2A6E 00 Front Faceplate Power Front Control 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 B2A6B, B2A6C The BCM is awake and communicating The user interface control is awake and communicating System voltage = 9 – 16 V B2A6E The BCM is awake and communicating The user interface control is awake and communicating System voltage = 9 – 16 V DTCs B2A6B, B2A6C are not set Conditions for Setting the DTC B2A6B The BCM receives a switch signal voltage message too high out of the expected range B2A6C The BCM receives a switch signal voltage message too low out of the expected range B2A6E 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. 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. DTC B2A6E 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 Testing

  1. Ignition OFF and all vehicle systems OFF, disconnect the connector at the A26 Heater and Air Conditioning User Interface Controls– Front. Ignition ON/ Vehicle in Service Mode.
  2. Test for 4.8–5.2 V between the signal circuit terminal 6 and ground. ⇒ If less than 4.8 V 2.1. Test circuit 4636 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 2.2. Test circuit 4636 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 2.3. Replace the K9 Body Control Module ⇒ If greater than 5.2 V 2.1. Test circuit 4636 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 2.2. Replace the K9 Body Control Module ⇓ If between 4.8–5.2 V
  3. Replace the A26 Heater and Air Conditioning User Interface Controls– Front. 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