Heated/Cooled Seat Always on

Heated/Cooled Seat Always On

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

1. Ignition OFF, disconnect the harness connector at the appropriate seat cushion or seat back ventilation heat and cool module.
2. Connect a test lamp between the control circuit terminal 7 and ground.

Important: The ignition must be cycled OFF then ON between each test in order to reset the CCS module.

3. Ignition ON, press the HEAT switch. The test lamp should illuminate or slowly illuminate for approximately 5 seconds.

• If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the CCS module.

• If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the CCS module.

4. If all circuits test normal, replace the CCS module.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Control Module References for CCS module replacement, setup, and programming. Programming and Relearning