Comfort Rear Seat Module
DESCRIPTION
The Comfort Rear Seat Module (CRSM) (3) is located under the cushion frame of both second row seats and are serviced similarly.
The CRSM is a Controller Area Network - Interior High Speed (CAN-IHS) bus microcontroller providing outputs to the heated seat pads, and ventilating. The CRSM receives commands over the CAN-IHS bus from the Body Control Module (BCM). The seat thermistor is hard wired to the CRSM.
OPERATION
The CRSM operates on fused battery current received from the ignition switch. The module is grounded to the body at all times through the electrical connector. Inputs to the module include CAN-IHS bus data bus messages and standard hardwired 12 volt power and ground. In response to inputs, the CRSM will control the battery current to the appropriate heated seat elements.
When a heated seat switch IHS data bus signal is received by the CSRM, the module energizes the selected heated seat element. The Low heat set point is about 38°C (100.4°F), and the High heat set point is about 42°C (107.6°F).
There are three levels of heat for both rear seats LO, Medium, and HI. Each level will remain in the selected state for the entire ignition cycle as long as the customer does not change it. The selected heat cycle does not automatically transition to the next heat cycle based on time or temperature.
In addition to operating the heated seat elements, the heated seat module sends LED illumination messages to the IPC. The IPC then sends the LED illumination message to the Integrated Center Stack (ICS) so that the appropriate LEDs are illuminated for any given heating level LO, Medium, or HI.
If the CRSM detects a heated seat element OPEN or SHORT circuit, it will record and store the appropriate Diagnostic Trouble Code (DTC).
The CRSM is diagnosed using a scan tool. If the module detects a heated seat element OPEN or SHORT circuit, the system will turn off and it will record and store the appropriate Diagnostic Trouble Code (DTC).
Heated Seats - The CRSM uses a Pulse Width Modulation (PWM) to provide power to the seat cushion and back heating elements. The temperature sensor thermistor is located in the seat cushion. The thermistor sensor feedbacks from each seat heating element to the CRSM to regulate the heater outputs to prevent any seat temperature to rise above set points. Seat heating has three selectable heat settings which are LO, Medium, and HI. Depending on thermistor reading, the CRSM will start the heater output by adjusting the PWM heat level according to the calibration table.
Vented Seats - The CRSM vents the two rear seats by providing variable analog voltages driving the external blowers in the seats. The seat venting has three selectable speeds for the fans LO, Medium, and HI. For seat venting, each press of the switch button will cause the seat to change venting modes. The CRSM will turn on the vented seats only with the engine running.
Rear Seat Heat Systems
- The element consists of a cushion element connected in parallel with a back element.
- The seat cushion and seat back have a thermistor to provide feedback to the CRSM.
- The seat cushion and seat back has a thermostat to automatically open the feed to the heated seat system.
- The heated seat cushion and seat back have a thermostat to automatically open the feed to turn the heated seat system off if the temperature reaches or exceeds the operating parameters programmed to the CRSM.