The heat and cool seat functions for the driver and passenger seats are controlled by the climate control seat module (CCSM) that is located under the passenger seat cushion. When a driver or passenger heat or cool seat switch is pressed, a low reference signal is applied through the switch signal circuit to the door control module. In response to the switch input, the door module illuminates the heated/cooled switch indicators and sends a serial data message to the memory seat module (MSM) indicating the heat/cool seat request. The MSM then sends a pulse width modulation (PWM) signal through the heated/cooled seat mode signal circuit to the CCSM. The CCSM then applies battery positive voltage to the seat cushion and seat back thermal electronic devices (TEDs) and a pre-determined voltage to the blower motors. To determine seat temperature, the CCSM supplies a 5 V signal and a low reference to the temperature sensors that are attached to each TED. The temperature sensors are variable resistors, their resistance changes as the temperature of the seat changes. Then based on the seat temperature, the CCSM controls the voltage level that it applies to the TEDs and blower motors.

Schematic Reference

Heated/Cooled Seat Schematics

Connector End View Reference

Heated/Cooled Seat Connector End Views

Description and Operation

Heated/Cooled Seats Description and Operation

Electrical Information Reference

Scan Tool Reference

1. If both, the driver and passenger heated and cooled seats are inoperative, refer to Driver and Passenger Heated/Cool Seats Inoperative.
2. Ignition ON, observe the scan tool Driver Door Switch parameters listed below while pressing and releasing the appropriate switch. The readings should change between Inactive and Active or Off and ON.

•	Seat Back Heat Mode Sw.

•	Seat Cool Mode Switch

•	Seat Heat Mode Sw.

⇒	If the reading does not change between Inactive and Active or Off and ON, refer to the Seat Temperature Control Switch component test. If the switch tests normal, replace the driver door module.

3. Operate the driver heated/cooled seat in the three modes listed below for greater than 1.5 minutes each. Verify that no DTCs are set between each test, and the appropriate heat or cool seat mode operates.

•	Seat Back and Cushion Heat Mode

•	Seat Back Only Heat Mode

•	Seat Cool Mode

⇒	If DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

⇒	If a heated and cooled seat mode is inoperative, refer to Heated and Cooled Seat Malfunction.

4. Observe the scan tool Passenger Door Switch parameters listed below while pressing and releasing the appropriate switch. The readings should change between Inactive and Active or Off and ON.

•	Seat Back Heat Mode Sw.

•	Seat Cool Mode Switch

•	Seat Heat Mode Sw.

⇒	If the reading does not change between Inactive and Active or Off and ON, refer to the Seat Temperature Control Switch component test. If the switch tests normal, replace the front passenger door module.

5. Operate the passenger heated/cooled seat in the three modes listed below for greater than 1.5 minutes each. Verify that no DTCs are set between each test, and the appropriate heat or cool seat mode operates.

•	Seat Back and Cushion Heat Mode

•	Seat Back Only Heat Mode

•	Seat Cool Mode

⇒	If DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

⇒	If a heated or cooled seat mode is inoperative, refer to Heated and Cooled Seat Malfunction.

6. If all heated and cooled seat functions operate normal, but the heated/cooled seat switch indicators do not illuminate or are always ON, refer to Heated/Cooled Seat Switch Indicator Malfunction.

Driver and Passenger Heated/Cool Seats Inoperative

1. Ignition OFF, disconnect the C1 harness connector at the CCSM.
2. Ignition OFF, test for less than 5 Ω between the ground circuit terminal M 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 E and ground.

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

4. Disconnect the C2 harness connector at the CCSM.
5. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 1 and ground.

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

6. If all circuits test normal, replace the CCSM.

Heated and Cooled Seat Malfunction

1. Ignition OFF, disconnect the C3 harness connector at the CCSM.
2. Connect a test lamp between the appropriate signal circuit terminal listed below and B+.

•	Driver heated/cooled seat mode signal terminal 14

•	Passenger heated/cooled seat mode signal terminal 6

3. Ignition ON, press the HEAT or COOL 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 signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the MSM.

⇒	If the test lamp is ON with the switch in the OFF position, test the signal circuit for a short to ground. If the circuit tests normal, replace the MSM.

4. Ignition OFF, connect the C3 harness connector at the CCSM.
5. Disconnect the harness connector at the seat cushion ventilation heat and cool module.
6. Connect a test lamp between the control circuit terminal 1 and ground.
7. Ignition ON, command the appropriate Driver or Passenger Seat Heat Cmd. ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CCSM.

8. Connect a test lamp between the control circuit terminal 3 and ground
9. Command the appropriate Driver or Passenger Seat Cool Cmd. ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CCSM.

10. Ignition OFF, connect the harness connector at the seat cushion ventilation heat and cool module.
11. Disconnect the harness connector at the seat back ventilation heat and cool module.
12. Connect a test lamp between the control circuit terminal 1 and ground.
13. Ignition ON, command the appropriate Driver or Passenger Seat Heat Cmd. ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CCSM.

14. Connect a test lamp between the control circuit terminal 3 and ground
15. Command the appropriate Driver or Passenger Seat Cool Cmd. ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the CCSM.

16. If all circuits test normal, test or replace the appropriate seat cushion or seat back ventilation heat and cool module.

Seat Temperature Control Switch

1. Ignition OFF, disconnect the C4 harness connector at the appropriate door module.
2. Test for infinite resistance between the low reference circuit terminal 4 and the signal terminals listed below the with the switch in the open position.

•	Seat back only mode switch terminal 7

•	Seat back cushion heat switch terminal 6

•	Seat cool switch terminal 3

⇒	If not the specified value, replace the seat temperature control switch.

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

•	Seat back only mode switch terminal 7

•	Seat back cushion heat switch terminal 6

•	Seat cool switch terminal 3

⇒	If greater than the specified range, replace the seat temperature control switch.

4. Connect a 3A fused jumper wire between the low reference circuit terminal 4 and ground.
5. Connect a test lamp between B+ and each control terminal listed below. The appropriate indicator should illuminate.

•	Seat back only mode indicator terminal 11

•	Seat cool mode indicator terminal 12

•	Seat back and cushion indicator terminal 10

•	Low temperature indicator terminal 9

•	Medium temperature indicator terminal 1

•	High temperature indicator terminal 2

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

Ventilation Heat and Cool Module

1. Ignition OFF, disconnect the harness connector at the appropriate seat cushion or seat back ventilation heat and cool module.

Important: If the resistance is measured with the seat still warm or cool, the resistance values will vary. At 68°F (20°C), the nominal resistance value is 1200 Ω ±5 percent. For warmer or cooler ambient temperatures, refer to the Temperature vs Resistance table below. The delta resistance values between the seat cushion and seat back temperature sensors should not be greater than 2000 Ω.

2. Test for 300 Ω - 18 kΩ between the temperature sensor signal circuit terminal 5 and the low reference circuit terminal 8.

⇒	If not within the specified range, replace the ventilation heat and cool module.

Important: The test leads must be connected in the correct polarity, otherwise lower out of range values will appear. Use the Positive Lead for the COOL control circuit and the Negative Lead for the HEAT control circuit. If the resistance is measured with the seat still warm or cool, the resistance values will vary even if the system was powered up for just a few seconds. The TED must be allowed to stabilize to room temperature prior to a measurement. The following conditions will change the resistance to out of range values:

•	The test leads are incorrectly connected.

•	Air blowing across the TED

•	Measuring the resistance at other than room temperature of 70°F

•	Holding the TED portion of the heated and cool ventilation module in your hand

In warmer or cooler climates where room temperature conditions of 70°F (21°C) may be unattainable, resistance values may read above the specified range. Use a heat gun or a blower to warm or cool the TED while measuring the resistance. The resistance values should slowly lower toward the specified range.
3. Test for 0.9 - 10 Ω between the heat control circuit terminal 1 and the cool control circuit terminal 3.

⇒	If not within the specified range, replace the ventilation heat and cool module.

Important: The test leads must be connected in the correct polarity, otherwise higher out of range values will appear. Use the Positive Lead for the control circuit and the Negative Lead for the ground circuit.

4. Test for 6 k - 9 kΩ between blower motor control circuit terminal 2 and the low reference circuit terminal 4.

⇒	If not within the specified range, replace the ventilation heat and cool module.

Important: The test leads need to be connected in the correct polarity, otherwise higher out of range values will appear. Use the Positive Lead for the speed control circuit and the Negative Lead for the ground circuit.

5. Test for 290 k - 420 kΩ between blower motor speed control circuit terminal 7 and the low reference circuit terminal 4.

⇒	If not within the specified range, replace the ventilation heat and cool module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.