Circuit/System Testing: Notes

Heated Cooled Seat Indicator Circuit Test

1. Ignition ON, verify that the HVAC module driver and passenger heated seat switch parameters display Active while any of the heated cooled seat switches are pressed.
   • If either of the switch parameters are continuously Active or Inactive while any of the headed cooled seat switches are pressed, replace the HVAC control module.
2. Verify that the MSM driver and passenger seat HVC mode and level parameters are displayed correctly as the heated cooled seat switches are activated through all of the operating modes.
   • If the MSM parameters are not displayed correctly replace the MSM.
3. If the circuits test normal replace the HVAC control module

Driver and Passenger Heated/Cool Seats Circuit Test

1. Ignition OFF, disconnect the C1 harness connector at the CCSM.
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 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 CCS module.

Driver Heated/Cool Seat Circuit Test

1. Ignition OFF, disconnect the C1, C2, C3 harness connectors at the CCSM.
2. Connect a test lamp between the heated/cooled seat mode signal circuit terminal 14 (C3) and battery voltage.
3. 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.
4. Test for 300 ohms to 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 heat/cool seat ventilation blower.
   • If the resistance measures less than the specified value, test or replace the appropriate heat/cool seat ventilation blower.
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 heat/cool seat ventilation blower 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.
5. Test for 0.9-10.0 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 heat/cool seat ventilation blower.
   • If less than 0.9 ohm, test or replace the appropriate heat/cool seat ventilation blower.
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 CCSM.
8. Disconnect the harness connector at the seat cushion heat/cool seat ventilation blower.
9. Ignition OFF, test for less than 5 ohms of resistance between the blower motor low reference circuit terminal G and ground.
   • If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the CCSM.
10. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.
    • If greater than 5.2 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
    • If less than 4.8 volts, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
11. Ignition ON, connect a test lamp between the following control circuits and ground. The test lamp should illuminate or slowly illuminate for approximately 2-4 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 A seat cushion heat control circuit
    • Terminal B seat cushion cool control circuit
    • If the test lamp does not illuminate, replace the CCSM.
    • If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
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 H seat cushion blower motor supply voltage
    • Terminal D 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 CCSM.
    • If the test lamp is always ON, test the appropriate circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
13. Connect the harness connector to the seat cushion heat/cool seat ventilation blower.
14. Disconnect the harness connector at the seat back heat/cool seat ventilation blower.
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 CCSM.
16. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.
    • If greater than 5.2 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
    • If less than 4.8 volts, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
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 A seat back heat control circuit
    • Terminal B seat back cool control circuit
    • If the test lamp does not illuminate, replace the CCSM.
    • If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
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 H seat back blower motor supply voltage circuit
    • Terminal D 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 CCSM.
    • If the test lamp is always ON, test the appropriate circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
19. If all circuits test normal, test or replace the appropriate heat/cool seat ventilation blower.

Passenger Heated/Cool Seat Circuit Test

1. Ignition OFF, disconnect the C1, C2, C3 harness connectors at the CCSM.
2. Connect a test lamp between the heated/cooled seat mode signal circuit terminal 6 (C3) and battery voltage.
3. 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.
4. Test for 300 ohms to 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 3.
   • Connector C2 seat back temperature sensor signal circuit terminal 9 and low reference circuit terminal 5.
   • 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 heat/cool seat ventilation blower.
   • If the resistance measures less than the specified value, test or replace the appropriate heat/cool seat ventilation blower.
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 heat/cool seat ventilation blower 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.
5. Test for 0.9-10.0ohms of resistance between the following heat control and cool control circuits.
   • Connector C1: Seat cushion heat control circuit terminal A and cool control circuit terminal B.
   • Connector C1: Seat back heat control circuit terminal C and cool control circuit terminal D.
   • If greater than 10 ohms, test the control circuits for an open/high resistance. If the circuits test normal, test or replace the appropriate heat/cool seat ventilation blower.
   • If less than 0.9 ohm, test or replace the appropriate heat/cool seat ventilation blower.
6. Test for infinite resistance between the following circuits and ground.
   • Connector C1:
     • Seat cushion heat control circuit terminal A
     • Seat cushion cool control circuit terminal B
     • Seat back heat control circuit terminal C
     • Seat back cool control circuit terminal D
   • Connector C2:
     • Seat cushion temperature sensor signal circuit terminal 2
     • Seat back temperature sensor signal circuit terminal 4
   • Connector C3:
     • Seat cushion blower motor speed control circuit terminal 3
     • Seat back blower motor speed control circuit terminal 4
     • Blower motor supply voltage circuit terminal 8
   • If less than infinite, test the appropriate circuit for a short to ground.
7. Connect the C1, C2, C3 harness connectors to the CCSM.
8. Disconnect the harness connector at the seat cushion heat/cool seat ventilation blower.
9. Ignition OFF, test for less than 5 ohms of resistance between the blower motor low reference circuit terminal G and ground.
   • If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the CCSM.
10. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.
    • If greater than 5.2 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
    • If less than 4.8 volts, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
11. Ignition ON, connect a test lamp between the following control circuits and ground. The test lamp should illuminate or slowly illuminate for approximately 2-4 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 A seat cushion heat control circuit
    • Terminal B seat cushion cool control circuit
    • If the test lamp does not illuminate, replace the CCSM.
    • If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
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 H seat cushion blower motor supply voltage
    • Terminal D 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 CCSM.
    • If the test lamp is always ON, test the appropriate circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
13. Connect the harness connector to the seat cushion heat/cool seat ventilation blower.
14. Disconnect the harness connector at the seat back heat/cool seat ventilation blower.
15. Ignition OFF, test for less than 5 ohms of resistance between the blower motor low reference circuit terminal H and ground.
    • If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the CCSM.
16. Ignition ON, test for 4.8-5.2 volts between the temperature sensor signal circuit terminal C and ground.
    • If greater than 5.2 volts, test the signal circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
    • If less than 4.8 volts, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
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 A seat back heat control circuit
    • Terminal B seat back cool control circuit
    • If the test lamp does not illuminate, replace the CCSM.
    • If the test lamp is always ON, test the appropriate control circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
IMPORTANT: The ignition must be cycled OFF then ON between each test in order to reset the CCSM.
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 H seat back blower motor supply voltage circuit
    • Terminal D seat back 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 CCSM.
    • If the test lamp is always ON, test the appropriate circuit for a short to voltage. If the circuit tests normal, replace the CCSM.
19. If all circuits test normal, test or replace the appropriate heat/cool seat ventilation blower.