Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

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

Connector End View Reference

Power Seat Connector End Views

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 Circuit Test.

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 ar heated or 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 Circuit Test.

5. Operate the passenger heated/cooled seat in the three modes listed below for greater than 1.5 minutes in 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 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. 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.

Seat Temperature Control Switch Circuit Test

1. Ignition OFF, disconnect the harness connector at the appropriate seat temperature control switch.
2. Verify that a test lamp illuminates between the appropriate low reference circuit terminal listed below and B+:

•	Driver seat temperature control switch terminal 3

•	Passenger seat temperature control switch terminal 5

⇒	If the test lamp does not illuminate, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the door module.

3. Ignition ON, verify the appropriate scan tool Driver or Passenger Door Switch parameters listed below are Inactive or Off:

•	Seat Back Heat Mode Sw.

•	Seat Cool Mode Switch

•	Seat Heat Mode Sw.

⇒	If not the specified value, test the appropriate signal circuit listed below for a short to ground. If the circuit tests normal, replace the door module.

•	Driver seat back only heat mode switch terminal 11

•	Driver seat cool switch terminal 14

•	Driver seat back and cushion switch terminal 8

•	Passenger seat back only heat mode switch terminal 11

•	Passenger seat cool switch terminal 8

•	Passenger seat back and cushion switch terminal 14

4. Install a 3A fused jumper wire between the signal circuit terminal 11 and ground. Verify the scan tool Seat Back Heat Mode Sw. parameter is Active.

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the door module.

5. Install a 3A fused jumper wire between the appropriate signal circuit listed below and ground. Verify the scan tool Seat Cool Mode Switch parameter is On.

•	Driver seat cool switch signal terminal 14

•	Passenger seat cool switch signal terminal 8

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the door module.

6. Install a 3A fused jumper wire between the appropriate signal circuit listed below and ground. Verify the scan tool Seat Heat Mode Sw. parameter is Active.

•	Driver seat back and cushion switch signal terminal 8

•	Passenger seat back and cushion switch signal terminal 14

⇒	If not the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the door module.

7. If all circuits test normal, test or replace the seat temperature control switch.

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 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.

Driver Seat Temperature Control Switch

1. Ignition OFF, disconnect the harness connector at the driver seat temperature control switch.
2. Test for infinite resistance between the signal circuits listed below and the low reference circuit terminal 3 with the switch in the open position.

•	Heated seat back only mode switch signal terminal 11

•	Heated seat back and cushion switch signal terminal 8

•	Heated seat cool switch signal terminal 14

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

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

•	Heated seat back only mode switch signal terminal 11

•	Heated seat back and cushion switch signal terminal 8

•	Heated seat cool switch signal terminal 14

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

Passenger Seat Temperature Control Switch

1. Ignition OFF, disconnect the harness connector at the passenger seat temperature control switch.
2. Test for infinite resistance between the signal circuits listed below and the low reference circuit terminal 5 with the switch in the open position.

•	Heated seat back only mode switch signal terminal 11

•	Heated seat back and cushion switch signal terminal 14

•	Heated seat cool switch signal terminal 8

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

3. Test for less than 2.0 Ω between the signal circuits listed below and the low reference circuit terminal 5 with the switch in the closed position.

•	Heated seat back only mode switch signal terminal 11

•	Heated seat back and cushion switch signal terminal 14

•	Heated seat cool switch signal terminal 8

⇒	If greater than the specified value, replace the passenger 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 supply voltage circuit and the Negative Lead for the ground circuit.

4. Test for 6 k - 9 kΩ between blower motor supply voltage 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.