Heated/Cooled Seats Inoperative 1
Heated/Cooled Seats Inoperative
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
Circuit/System Description
The heat and cool seat functions for both driver and passenger seats are controlled by the climate control seat module 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 sends a GMLAN 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 climate control seat (CCS) module. The CCS module 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 CCS module 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 CCS module 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 (CCS) system, the ignition must be cycled OFF then ON between each test in order to reset the CCS module.
* A short to battery voltage on a temperature sensor signal circuit may open the sensor.
Circuit/System Testing
Driver and Passenger Heated/Cool Seats are Inoperative
1. Ignition OFF, disconnect the (C1) harness connector at the CCS module.
2. Ignition OFF, test for less than 5 ohms of resistance between the ground circuit terminal M and ground.
• If greater than 5 ohms, 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. Ignition OFF, disconnect the (C2) harness connector at the CCS module.
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 CCS module.
Driver Heated/Cooled Seat Inoperative
1. Ignition ON, observe the following scan tool parameters in the Driver Door Switch data list while pressing and releasing the related switch. The readings should change between Active and Inactive.
* Seat Back Heat Mode Sw.
* Seat Cool Mode Switch.
* Seat Heat Mode Sw.
• If not Active or always Active, perform the Heated and Cooled Seat Switch Component Test.
2. Ignition OFF, disconnect the (C1, C2, C3) harness connectors at the CCS module.
3. Connect a test lamp between the heated/cooled seat mode signal circuit terminal 14 (C3) and battery voltage.
4. 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.
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 hotter or colder 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.
5. Test for 300 ohms - 18K ohms of resistance between the following temperature sensor signal and low reference circuits.
* Connector C2 seat cushion temperature sensor signal circuit terminal 7 and low reference circuit terminal 8.
* Connector C2 seat back temperature sensor signal circuit terminal 9 and low reference circuit terminal 10.
• If the resistance is greater than the specified value, test the sensor signal circuit and low reference circuit for a short to voltage or an open/high resistance. If the circuits test normal, test or replace the appropriate ventilation heat and cool module.
• If the resistance measures less than the specified value, test or replace the appropriate 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 (21°C).
* Holding the TED portion of the heated and cool ventilation module in your hand.
In hotter or colder 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.
Test for 0.9-10 ohms of resistance between the following heat control and cool control circuits.
* Connector C1: Seat cushion heat control circuit terminal G and cool control circuit terminal H.
* Connector C1: Seat back heat control circuit terminal J and cool control circuit terminal K.
• If greater than 10 ohms, test the control circuits for an open/high resistance. If the circuits test normal, test or replace the appropriate ventilation heat and cool module.
• If less than 0.9 ohm, test or replace the appropriate ventilation heat and cool module.
6. Test for infinite resistance between the following circuits and ground.
* Connector C1:
- Seat cushion heat control circuit terminal G
- Seat cushion cool control circuit terminal H
- Seat back heat control circuit terminal J
- Seat back cool control circuit terminal K
* Connector C2:
- Seat cushion temperature sensor signal circuit terminal 7
- Seat back temperature sensor signal circuit terminal 9
* Connector C3:
- Seat cushion blower motor speed control circuit terminal 11
- Seat back blower motor speed control circuit terminal 12
- Blower motor supply voltage circuit terminal 16
• If less than infinite, test the appropriate circuit for a short to ground.
7. Connect the (C1, C2, C3) harness connectors to the CCS module.
8. Disconnect the harness connector at the seat cushion ventilation heat and cool module.
9. Ignition OFF, test for less than 5 ohms of resistance between the blower motor low reference circuit terminal 4 and ground.
• If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the CCS module.
10. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal 5 and ground.
• If greater than 5.2 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCS module.
• If less than 4.8 volts, replace the CCS module.
Important: The ignition must be cycled OFF then ON between each test in order to reset the CCS module.
11. Ignition ON, connect a test lamp between the following control circuits and ground. The test lamp should illuminate or slowly illuminate for approximately 2 to 4 seconds after the switch is pressed. On the heat control circuit, the test lamp may exhibit a 4 second delay before it starts to illuminate.
Press the HEAT switch for heat control and the COOL switch for cool control.
* Terminal 1 seat cushion heat control circuit
* Terminal 3 seat cushion cool control circuit
• If the test lamp does not illuminate, replace the climate control seat module.
• If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the CCS module.
Important: The ignition must be cycled OFF then ON between each test in order to reset the CCS module.
12. Connect a test lamp between the following circuits and ground. The test lamp should illuminate or slowly illuminate for approximately 5 seconds after pressing the HEAT switch.
* Terminal 2 seat cushion blower motor supply voltage
* Terminal 7 seat cushion blower motor speed control
• If the test lamp does not illuminate, test the appropriate circuit for an open/high resistance. If the circuit tests normal, replace the CCS module.
• If the test lamp is always ON, test the appropriate circuit for a short to voltage. If the circuit tests normal, replace the CCS module.
13. Connect the harness connector to the seat cushion ventilation heat and cool module.
14. Disconnect the harness connector at the seat back ventilation heat and cool module.
15. Ignition OFF, test for less than 5 ohms of resistance between the blower motor low reference circuit terminal 4 and ground.
• If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the climate control module.
16. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal 5 and ground.
• If greater than 5.2 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCS module.
• If less than 4.8 volts, replace the CCS module.
Important: The ignition must be cycled OFF then ON between each test in order to reset the CCS module.
17. Ignition ON, connect a test lamp between the following control circuits and ground. The test lamp should illuminate or slowly illuminate for approximately 4 seconds after the switch is pressed. On the heat control circuit, the test lamp may exhibit a 4 second delay before it starts to illuminate.
Press the HEAT switch for heat control and the COOL switch for cool control.
* Terminal 1 seat back heat control circuit
* Terminal 3 seat back cool control circuit
• If the test lamp does not illuminate, replace the CCS module.
• If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the CCS module.
Important: The ignition must be cycled OFF then ON between each test in order to reset the CCS module.
18. Connect a test lamp between the following circuits and ground. The test lamp should illuminate or slowly illuminate for approximately 5 seconds after pressing the HEAT switch.
* Terminal 2 seat back blower motor supply voltage circuit
* Terminal 7 seat back blower motor speed control circuit
• If the test lamp does not illuminate, test the appropriate circuit for an open/high resistance. If the circuit tests normal, replace the CCS module.
• If the test lamp is always ON, test the appropriate circuit for a short to voltage. If the circuit tests normal, replace the CCS module.
19. If all circuits test normal, test or replace the appropriate ventilation heat and cool module.