The driver and front passenger heated seats are controlled by separate heated seat switches located on the door panels. When a heated seat switch is pressed, ground is momentarily applied through the switch contacts and the switch signal circuit to the door lock/window switch. In response to this signal, the door lock/window switch sends a serial message to the memory seat module (MSM) indicating the heat seat request. The MSM then applied battery voltage to the seat cushion and seat back heater elements through a common voltage supply circuit. Each individual heater element is grounded by the module through separate low side drive control circuits. The heater element control circuits are pulse width modulated (PWM) to ground by the module in order to control the seat temperatures by regulating the current flow through the heater elements. The MSM relies on 4 independent inputs from temperature sensors (thermistors) located in the seat back and seat cushion of the driver and passenger seats. The temperature sensor resistance varies based on the temperature of the heating element causing the signal circuit voltage to change. Once the seat reaches the switch set temperature, the MSM will then cycle the control circuits of the heating elements ON and OFF in order to maintain the desired seat temperature based on the feedback voltage from the sensors. The MSM then monitors the current flow through the heating elements and the of rate change of the temperature sensor to verify correct heated seat operation.

Schematic Reference

Heated/Cooled Seat Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Heated Seats Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the appropriate scan tool Driver Door Switch or Passenger Door Switch parameters listed below while pressing and releasing the appropriate switch. The readings should change between Inactive and Active.

•	Seat Back Heat Mode Sw.

•	Seat Heat Mode Sw.

⇒	If not the specified values, refer to the Heated Seat Switch component test. If the heated seat switch tests normal, replace the appropriate door lock/window switch.

2. If all scan tool parameters test normal and there are no DTCs set, replace the MSM.
3. If all heated seat functions operate normal and the heated seat switch indicators do not illuminate, refer to the Heated Seat Switch Indicators component test.

Heated Seat Switch

1. Ignition OFF, disconnect the X4 harness connector at the appropriate door lock/window switch.
2. Test for infinite resistance between the signal circuits listed below and the low reference circuit terminal 4 with the switch in the open position.

•	Seat back and cushion heat mode terminal 6

•	Seat back only mode terminal 7

⇒	If not the specified value, replace the heated seat switch.

3. Test for less than 2 Ω between the signal circuits listed below and the low reference circuit terminal 4 with the switch in the closed position.

•	Seat back and cushion heat mode terminal 6

•	Seat back only mode terminal 7

⇒	If greater than the specified range for any of the tests, replace the heated seat switch.

Heated Seat Switch Indicators

1. Ignition OFF, disconnect the X4 harness connector at the appropriate door lock/window switch.
2. Connect a 3 A fused jumper wire between the low reference circuit terminal 4 and ground.
3. Connect a test lamp between B+ and each control circuit listed below. The appropriate indicator should illuminate.

•	Seat back and cushion mode indicator terminal 10

•	Seat back only mode indicator terminal 11

•	Low heat indicator terminal 9

•	Medium heat indicator terminal 1

•	High heat indicator terminal 2

⇒	If any indicator does not illuminate, replace the heated seat switch.

4. If all indicators illuminate, replace the door lock/window switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.