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Tahoe / Yukon Service Manual

Vented Seat Malfunction

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. Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
1139 B+ 1, 4 1, 2, 3, 4, 5, 6 — —
5906 Control 1 1, 2, 3 1 —
5908 Control 4 4, 5, 6 4 —
1150 Ground — 1, 2, 3 — —
1250 Ground — 4, 5, 6 — —
1. Driver Seat back and cushion ventilation functions are inoperative 2. Driver Seat back ventilation function is inoperative 3. Driver Seat cushion ventilation function is inoperative 4. Passenger Seat back and cushion ventilation functions are inoperative 2. Passenger Seat back ventilation function is inoperative 3. Passenger Seat cushion ventilation function is inoperative

Scan Tool Data K9 Body Control Module Normal Operation Data List Parameter Values

Data List Parameter Values Normal Operation
Seat Heating/Venting/Cooling Data Driver Seat Heating/Venting/C Mode Off / Seat Back and Cushion ooling Heating / Seat Venting/Cooling This parameter indicates the type of Heated/Vented Seat function being applied as commanded by the BCM.
Passenger Seat Heating/Venting/C Mode Off / Seat Back and Cushion ooling Heating / Seat Venting/Cooling This parameter indicates the type of Heated/Vented Seat function being applied as commanded by the BCM.

Circuit/System Description The driver and front passenger vented seats are controlled by separate vented seat switches that are located in the A26 Heater and Air Conditioning User Interface Control - Front. When a vented seat switch is pressed, a LIN Bus serial message is sent from the A26 Heater and Air Conditioning User Interface Control - Front to the K9 Body Control Module. The K9 Body Control Module serves as the heated/vented seat system master to determine the requested operating mode. The K9  Body Control Module then sends a LIN bus serial data message to the K29FV Front Seat Heater Vent Control Module indicating the vented seat command. In response to this message, the K29FV Front Seat Heater Vent Control Module applies a low side drive pulse width modulation (PWM) signal through the blower motor control circuit to the seat back and cushion blower motors indicating the seat ventilation command. The logic in the blower motors sets the blower speed to the switch set point. The K9 Body Control Module then sends a serial data message back to the A26 Heater and Air Conditioning User Interface Control - Front to either illuminate or turn off the appropriate temperature indicator. 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 that no DTCs are set for the heated/vented seat system. ⇒ If DTCs are set for the heated/vented seat system Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no DTCs are set
  3. Verify the heated seat system operates. ⇒ If the heated seat system does not operate Refer to Front Heated Seat Malfunction ⇓ If the heated seat system operates
  4. Verify the appropriate scan tool Body Control Module parameter listed below changes state when pressing the vented seat switch. Driver Seat Heating/Venting/Cooling Mode Passenger Seat Heating/Venting/Cooling Mode ⇒ If the parameter does not change Replace the A26 Heater and Air Conditioning User Interface Control - Front. ⇓ If the parameter changes
  5. Verify that the seat cushion and seat back blower motors turn ON and OFF. ⇒ If either or both the seat cushion and seat back blower motors are inoperative Refer to Circuit/System Testing ⇒ If the blower motors do not change speed or are always ON Refer to Circuit/System Testing ⇓ If the seat cushion and seat back blower motors operate
  6. A fault is currently not present and may be an intermittent condition. Circuit/System Testing
  7. Ignition OFF and all vehicle systems OFF, disconnect the appropriate two seat blower motors listed below: M73A Seat Blower Motor - Driver Back and M73C Seat Blower Motor - Driver Cushion M73B Seat Blower Motor - Passenger Back and M73D Seat Blower Motor - Passenger Cushion
  8. Verify a test lamp illuminates between the appropriate ground circuit terminals listed below and B+, one at a time. Terminal 3 at M73A Seat Blower Motor - Driver Back Terminal 3 at M73C Seat Blower Motor - Driver Cushion Terminal 3 at M73B Seat Blower Motor - Passenger Back Terminal 3 at M73D Seat Blower Motor - Passenger Cushion ⇒ If the test lamp does not illuminate 2.1. Test the appropriate circuit for an open/high resistance: Terminal 3 at M73A Seat Blower Motor - Driver Back = Circuit 1150 Terminal 3 at M73C Seat Blower Motor - Driver Cushion = Circuit 1150 Terminal 3 at M73B Seat Blower Motor - Passenger Back = Circuit 1250 Terminal 3 at M73D Seat Blower Motor - Passenger Cushion = Circuit 1250 2.2. Repair the open/high resistance in the ground connection. ⇓ If the test lamp illuminates
  9. Verify a test lamp illuminates between the appropriate B+ circuit terminals listed below and ground, one at a time. Terminal 1 at M73A Seat Blower Motor - Driver Back Terminal 1 at M73C Seat Blower Motor - Driver Cushion Terminal 1 at M73B Seat Blower Motor - Passenger Back Terminal 1 at M73D Seat Blower Motor - Passenger Cushion ⇒ If the test lamp does not illuminate and the circuit fuse is good Repair the open/high resistance on the circuit 1139. ⇒ If the test lamp does not illuminate and the circuit fuse is open 3.1. Test the circuit 1139 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 M73 Seat Blower Motor.
  10. Connect a test lamp between the appropriate control circuit terminal and B+, one at a time. Terminal 2 at M73A Seat Blower Motor - Driver Back Terminal 2 at M73C Seat Blower Motor - Driver Cushion Terminal 2 at M73B Seat Blower Motor - Passenger Back Terminal 2 at M73D Seat Blower Motor - Passenger Cushion
  11. Ignition ON, Verify the test lamp turns ON when pressing the vented seat switch through the High, Medium, and Low positions and the test lamp turns OFF when the OFF position is reached. ⇒ If the test lamp does not turn ON 5.1. Test the appropriate circuit for a short to voltage: Terminal 2 at M73A Seat Blower Motor - Driver Back = Circuit 5906 Terminal 2 at M73C Seat Blower Motor - Driver Cushion = Circuit 5906 Terminal 2 at M73B Seat Blower Motor - Passenger Back = Circuit 5908 Terminal 2 at M73D Seat Blower Motor - Passenger Cushion = Circuit 5908 ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found 5.2. Test the appropriate circuit for an open/high resistance: Terminal 2 at M73A Seat Blower Motor - Driver Back = Circuit 5906 Terminal 2 at M73C Seat Blower Motor - Driver Cushion = Circuit 5906 Terminal 2 at M73B Seat Blower Motor - Passenger Back = Circuit 5908 Terminal 2 at M73D Seat Blower Motor - Passenger Cushion = Circuit 5908 ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 5.3. Replace the K29FV Front Seat Heater Vent Control Module. ⇒ If the test lamp does not turn OFF 5.1. Test the appropriate circuit for a short to ground: Terminal 2 at M73A Seat Blower Motor - Driver Back = Circuit 5906 Terminal 2 at M73C Seat Blower Motor - Driver Cushion = Circuit 5906 Terminal 2 at M73B Seat Blower Motor - Passenger Back = Circuit 5908 Terminal 2 at M73D Seat Blower Motor - Passenger Cushion = Circuit 5908 ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 5.2. Replace the K29FV Front Seat Heater Vent Control Module. ⇓ If the test lamp turns ON and OFF
  12. Replace the appropriate malfunctioning seat blower motor. M73A Seat Blower Motor - Driver Back M73C Seat Blower Motor - Driver Cushion M73B Seat Blower Motor - Passenger Back M73D Seat Blower Motor - Passenger Cushion Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Front Seat Back Ventilation Blower Replacement Front Seat Cushion Ventilation Blower Replacement Control Module References for K29FV Front Seat Heater Vent Control Module replacement, programming and setup