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Vented Seat Malfunction (With Memory)

Vented Seat Malfunction (With Memory)

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 Short to Ground Open/High Resistance Short to Voltage Signal Performance
Ignition Voltage

1, 4

1, 4

-

-

Driver Seat Back Blower Motor Ignition Voltage

1, 4

2

-

-

Driver Seat Cushion Blower Motor Ignition Voltage

1, 4

3

-

-

Driver Vented Seat Control

1

1

1

-

Driver Seat Back Blower Motor Ground

-

2

-

-

Driver Seat Cushion Blower Motor Ground

-

3

-

-

Passenger Seat Back Blower Motor Ignition Voltage

1, 4

5

-

-

Passenger Seat Cushion Blower Motor Ignition Voltage

1, 4

6

-

-

Passenger Vented Seat Control

4

4

4

-

Passenger Seat Back Blower Motor Ground

-

5

-

-

Passenger Seat Cushion Blower Motor Ground

-

6

-

-

1. Driver vented seat is inoperative

2. Driver vented seat back is inoperative

3. Driver vented seat cushion is inoperative

4. Passenger vented seat is inoperative

5. Passenger vented seat back is inoperative

6. Passenger vented seat cushion is inoperative



Circuit/System Description

The driver and passenger vented seats are controlled by separate vented seat switches located in the HVAC control. Ignition voltage is supplied to the driver and passenger seat blower motors through a 10 A fuse located in the underhood fuse block. When a vented seat switch is pressed, a serial data message is sent from the HVAC control 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 HVAC control to either illuminate or turn off the appropriate switch indicator.

Reference Information

Schematic Reference

Heated/Cooled Seat Schematics

Connector End View Reference

Component Connector End Views

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. Engine 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.

2. If not the specified value, replace the A26 HVAC control.

3. Observe the scan tool Passenger Seat Heating/Venting/Cooling Mode parameter while pressing the passenger VENTED seat switch. The reading should change between Off and Vent/Cool.

4. If not the specified value, replace the A26 HVAC control.

5. If all scan tool parameter readings test normal and the driver and/or passenger vented seat is inoperative, refer to Circuit/System Testing.


Circuit/System Testing


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 Ω between the ground circuit terminal 2 and ground.

3. If greater than the specified range, test the ground circuit for an open/high resistance.

4. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.

5. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

6. Connect a test lamp between the control circuit terminal 3 and B+.

7. Engine ON, 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.

8. 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.

9. 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.

10. If all circuits test normal, test or replace the M73 blower motor.


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


Heater and Air Conditioning Control Replacement

Control Module References for seat memory control module replacement, setup, and programming