Vented Seat Malfunction
Vented Seat Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
With the ignition in the ON position, ignition voltage is applied to the ignition main relay energizing the relay. With the relay energized, battery voltage is applied through the switch side of the relay, the 10 A DSM fuse, and the ignition circuit to the driver and passenger vented seat blower motors. The driver and passenger vented seats are controlled by separate vented seat switches located in the radio/HVAC controls. When a vented seat switch is pressed, a serial data message is sent from the radio/HVAC controls to the HVAC control module indicating the vented seat command. The HVAC control module serves as a gateway to transmit the message to the seat memory control module via the serial data line. In response to this message, the seat memory control module applies a low side pulse width modulation (PWM) signal through the blower motor control circuits to the seat cushion and seat back blower motors indicating the vented seat command. The logic in the blower motors then sets the blower speed to the switch set point. Both blower motors run drawing cabin air around and away from occupant. The seat memory control module then sends a serial data message back to the HVAC control module to gateway the information back to the radio/HVAC controls to either illuminate or turn off the appropriate switch indicator.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Heated/Vented Seat Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool Driver Seat Heating/Venting/Cooling Mode parameter while pressing the driver VENTED seat switch. The reading should change between Off and Vent/Cool.
• If not the specified value, replace the A20 radio/HVAC controls.
2. Observe the scan tool Passenger Front Seat Heating/Venting/Cooling Mode parameter while pressing the front passenger VENTED seat switch. The reading should change between Off and Vent/Cool.
• If not the specified value, replace the A20 radio/HVAC controls.
3. If all scan tool parameter readings test normal and the driver and/or passenger vented seat is inoperative, refer to the Circuit/System Testing.
Circuit/System Testing
Ignition ON, verify that a test lamp illuminates between the test points on the 10 A DSM fuse and ground.
If the test lamp does not illuminate, refer to the Ignition Main Relay Circuit Test.
If the test lamp illuminates, refer to the Blower Motor Circuit Test.
Ignition Main Relay Circuit Test
1. Ignition OFF, disconnect the KR73 ignition main relay.
2. Test for less than 5 Ohms between the ground circuit terminal 86 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Verify that a test lamp illuminates between the B+ circuit terminal 30 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 85 and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K9 BCM.
5. If all circuits test normal, test or replace the KR73 ignition main relay.
Blower Motor Circuit Test
1. Ignition OFF, disconnect the harness connector at the appropriate blower motor listed below:
* M73A seat blower motor - driver back
* M73C seat blower motor - driver cushion
* M73B seat blower motor - passenger back
* M73D seat blower motor - passenger cushion
2. Test for less than 5 Ohms between the ground circuit terminal B and ground.
• If greater than the specified value, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground.
• If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
4. Connect a test lamp between the control circuit terminal A and B+.
5. Press the VENTED seat switch through the high, medium, and low positions to OFF. The test lamp should illuminate until the OFF position is reached.
• If the test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K40 seat memory control module.
• If the test lamp remains ON with the switch in the OFF position, test the control circuit for a short to ground. If the circuit tests normal, replace the K40 seat memory control module.
6. If all circuits test normal, test or replace the M73 blower motor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Radio Control Assembly Replacement (Radio Control Assembly Replacement)
* Front Seat Vent Fan Replacement (Front Seat Vent Fan Replacement)
* Front Seat Back Cushion Vent Fan Replacement (Front Seat Back Cushion Vent Fan Replacement)
* Control Module References (Programming and Relearning) for seat memory control module replacement, setup, and programming