Heated and Cooled Seat Malfunction
Heated and Cooled Seat Malfunction
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* ReviewStrategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Diagnostic Fault Information
Circuit/System Description
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 this signal, 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-volt 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.
Diagnostic Aids
* In order to perform valid tests when diagnosing the climate control seat system, the ignition must be cycled OFF then ON between each test in order to reset the CCSM.
* Most circuit faults will set a DTC within 1.5 minutes. However, some circuit faults may cause a performance problem in one mode and be inoperative and set a DTC in another mode. In some cases it may take 5 minutes or more for a DTC to set. Operate the heated/cooled seat in each of the three modes for 5 minutes or more then check for DTCs.
Reference Information
Schematic Reference
Heated/Cooled Seat Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Heated/Cooled Seats Description and Operation (Heated/Cooled Seats Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning)for scan tool information
Circuit System Verification
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 Driver Heated and Cooled Seat Switch Test.
3. Operate the driver heated/cooled seat for more than 1.5 minutes in each of the three modes, then verify that no DTCs are set.
• If DTCs are set, Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) .
4. If the driver heated and cooled seat is inoperative, Refer to Heated/Cooled Seat Malfunction.
5. 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 Passenger Heated and Cooled Seat Switch Test.
6. Operate the passenger heated/cooled seat for more than 1.5 minutes in each of the three modes, then verify that no DTCs are set.
• If DTCs are set, Refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) .
7. If the passenger heated and cooled seat is inoperative, Refer to Heated/Cooled Seat Malfunction.
8. 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 the appropriate test listed below:
* Heated and Cooled Seat Switch Indicators Inoperative
* Heated and Cooled Seat Switch Indicators Always ON
Circuit/System Testing
Driver and Passenger Heated and Cool Seats Inoperative
1. Ignition OFF, disconnect the X1 harness connector at the CCSM.
2. Test for less than 5 ohms 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 X2 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 Switch Test
1. Ignition OFF, disconnect the harness connector at the appropriate heated and cooled seat switch.
2. Verify that a test lamp illuminates between the appropriate low reference circuit listed below and B+.
* Driver heated and cooled seat switch terminal 3
* Passenger heated and cooled seat 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 heated and cooled seat switch.
Heated and Cooled Seat Malfunction
1. Ignition OFF, disconnect the X3 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 X3 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.
Heated and Cooled Seat Switch Indicators Inoperative
1. Ignition OFF, disconnect the harness connector at the appropriate heated and cooled seat switch.
2. Verify that a test lamp illuminates between the appropriate low reference circuit listed below and B+.
* Driver heated and cooled seat switch terminal 3
* Passenger heated and cooled seat 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 appropriate DDM or FPDM.
3. Connect the harness connector at the heated and cooled seat switch.
4. Disconnect the X4 harness connector at the door module.
5. Connect a 3A fused jumper wire between the low reference circuit terminal 4 and ground.
6. Connect a test lamp between each indicator control circuit listed below and B+. The appropriate indicator should illuminate.
* Heated seat back only mode indicator terminal 11
* Heated seat cool mode indicator terminal 12
* Heated 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, test the appropriate control circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the heated and cooled seat switch.
7. If all indicators illuminate, replace the appropriate DDM or FPDM.
Heated and Cooled Seat Switch Indicators Always On
1. Ignition OFF, disconnect the harness connector at the appropriate driver or passenger heated and cooled seat switch.
2. Ignition ON, test for 0 volts between the appropriate indicator control circuit listed below and ground.
* Driver heated seat back only mode indicator terminal 4
* Driver heated seat cool mode indicator terminal 7
* Driver heated seat back and cushion indicator terminal 2
* Driver low temperature indicator terminal 13
* Driver medium temperature indicator terminal 6
* Driver high temperature indicator terminal 12
* Passenger heated seat back only mode indicator terminal 4
* Passenger heated seat cool mode indicator terminal 1
* Passenger heated seat back and cushion indicator terminal 6
* Passenger low temperature indicator terminal 9
* Passenger medium temperature indicator terminal 2
* Passenger high temperature indicator terminal 10
• If greater than the specified value, test the control circuit for a short to voltage. If the circuit tests normal, replace the appropriate DDM or FPDM.
Component Testing
Driver Heated and Cool Seat Switch
1. Ignition OFF, disconnect the harness connector at the heated and cooled seat 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 heated and cooled seat switch.
3. Test for less than 2 ohms 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 heated and cooled seat switch.
Passenger Heated and Cool Seat Switch
1. Ignition OFF, disconnect the harness connector at the heated seat 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 heated and cooled seat switch.
3. Test for less than 2 ohms 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 heated and cooled seat switch.
Ventilation Heat and Cool Module
1. Ignition OFF, disconnect the harness connectors at the seat cushion and seat back ventilation heat and cool modules.
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 ohms ±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 ohms.
2. Test for 300 ohms-18K ohms 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 0.9-10.0 ohms 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 6-9K ohms 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 290-420K ohms 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.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) Diagnostic Repair Verification after completing the diagnostic procedure.
* Heated and Cooled Seat Switch Replacement (Service and Repair)
* Driver or Passenger Seat Back Ventilation Heating and Cooling Blower Replacement (Driver or Passenger Seat Back Ventilation Heating and Cooling Blower Replacement)
* Driver or Passenger Seat Cushion Ventilation Heating and Cooling Blower Replacement (Driver or Passenger Seat Cushion Ventilation Heating and Cooling Blower Replacement)
* Control Module References (Programming and Relearning)for CCSM, MSM, DDM, and FPDM replacement, setup, and programming