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Tahoe / Yukon Service Manual

DTC B19CA-B19CD

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 B19CA Front Seat Cushion Heater - Driver DTC B19CB Front Seat Back Heater - Driver DTC B19CC Front Seat Cushion Heater - Passenger DTC B19CD Front Seat Back Heater - Passenger Symptom Byte Information: Symptom Byte List Circuit/System Description The driver and passenger heated seats switches are located within the A26 Heater and Air Conditioning User Interface Control - Front. To operate the heated seats the engine must be running. When a heated seat switch is pressed, a serial data message is sent from the A26 Heater and Air Conditioning User Interface Control - Front to the K9 Body Control Module (BCM) indicating the heated seat command. The BCM serves as the heated seat system master to determine the requested operating mode. The BCM then sends a LIN bus serial data message to the K29FV Front Seat Heater Vent Control Module indicating the heated seat command. In response to this message, the K29FV Front Seat Heater Vent Control Module attempts to drive the appropriate seat heating elements per the BCM command. The BCM also controls the seat temperature and mode indicators, via the serial data line, used to provide the operator with feedback as to the operating status of the system. The K29FV Front Seat Heater Vent Control Module controls heated seat operation for the driver and passenger seats. When active, power is applied to the seat cushion and back heater elements through a common pulse width modulated (PWM) voltage supply control circuit. Each individual heater element is switched to ground by the module through a common low side drive control circuit. The seat back and cushion temperature sensors (thermistors) are packaged with the seat heating elements located just under the seat covers. The K29FV Front Seat Heater Vent Control Module supplies each temperature sensor with a 5 V reference signal circuit and a low reference circuit. The module monitors the voltage from the signal circuit to determine the temperature of the seat. The temperature sensor varies in resistance based on the temperature of the heating element causing the signal voltage to change. Once the module senses the seat reached the set temperature, it will then begin regulate the current flow through the heater elements in order to maintain the desired seat temperature based on the feedback voltage from the sensor. Conditions for Running the DTC Engine ON. Heated Seat System ON. Conditions for Setting the DTC The front seat heater control module detects a fault within a heating element. Action Taken When the DTC Sets The front seat heater control module will disable all heated seat functions. Conditions for Clearing the DTC The DTC clears when the diagnostic runs and passes. The history DTC will clear after 40 consecutive fault-free ignition cycles have occurred. Diagnostic Aids If there are no wiring, terminal, or connection concerns found and the heating element has already replaced, suspect an issue with the K29FV Front Seat Heater Vent Control Module. Reference Information Schematic Reference Heated/Cooled Seat Schematics Connector End View Reference Master Electrical Component List Description and Operation Heated/Vented Seat 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 only DTCs B19CA, B19CB, B19CC, or B19CD are set. ⇒ If any other system DTC is set Diagnose all other system DTCs first. Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If only DTCs B19CA, B19CB, B19CC, or B19CD are set
  3. Clear all DTCs.
  4. Engine ON.
  5. Operate the Driver heated seat.
  6. Verify DTC B19CA and B19CB do not set. ⇒ If DTC B19CA sets Replace the E14B Front Seat Cushion Heater - Driver. ⇒ If DTC B19CB sets Replace the E14A Front Seat Back Heater - Driver. ⇓ If no DTC sets
  7. Operate the Passenger heated seat.
  8. Verify DTC B19CC and B19CD do not set. ⇒ If DTC B19CC sets Replace the E14D Front Seat Cushion Heater - Passenger. ⇒ If DTC B19CD sets Replace the E14C Front Seat Back Heater - Passenger. ⇓ If no DTC sets
  9. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Refer to Front Seat Back Heater Replacement Refer to Front Seat Cushion Heater Replacement