Heated Seats - Operation

OPERATION

FRONT SEAT HEATED SEAT SYSTEM OPERATION

The front heated seat system operates on battery current received through a fuse in the Integrated Power Module (IPM). Fused ignition switch output (run-acc) circuits are used, so that the systems will only operate when the ignition switch is in the ON or Accessory positions. The heated seat system will turn off automatically whenever the ignition switch is turned to any position except On or Accessory. The low heat position set point is about 36° C (97° F), and the high heat position set point is about 41° C (105° F).

When either of the front heated seat switches are depressed a resistance signal is sent to the applicable Door Module (Driver or Passenger). The applicable Door Module then sends a message via the Programmable Communications Interface (PCI) data bus network to the Memory Heated Seat Adjustable Pedal Module (MHSAPM), signaling the module to energize the heating element for the selected seat. Light Emitting Diodes (LED) in each switch indicate the level of heat in use. The switch LEDs are controlled by the applicable Door Module.

The MHSAPM energizes an integral solid-state relay, which supplies battery current to the seat heating elements. When high-temperature heating is selected, the heaters provide a boosted heat level during the first four minutes of operation after heating is activated. The heat output then drops to the normal selected-temperature level. If high-level heating is selected, the control system will automatically switch to the low level after two hours of continuous operation. Operation on the low setting turns off only when the ignition switch is turned off or the heated seat switch is pressed a second time indicating an off command.

The module will automatically turn off the heating elements if it detects an OPEN or LOW short in the heating element circuit.

2ND ROW HEATED SEAT SYSTEM OPERATION

The 2nd row heated seat system operates independently from the front heated seat system. The 2nd row heated seat module receives fused battery current through the Integrated Power Module only when the ignition switch is in the ON position. The heated seat module shares a common ground circuit with each of the heated seat elements. The heated seat system will only operate when the surface temperature of the seat cushion is below the designed temperature set points of the system. The low heat position set point is 35° C (95° F), and the high heat position set point is 40° C (104° F).

A separate heated seat module contains the control logic for the 2nd row heated seat system. The module responds to the heated seat switch status, ignition switch status, and the heated seat element sensor inputs by controlling the output to the 2nd row seat heating elements through integral solid-state relays.

When either of the 2nd row seat heated seat switches are depressed a resistance signal is sent to the heated seat module, signaling the module to energize the heating element for the selected seat.

The heated seat sensor provides the heated seat module with a low-voltage input indicating the surface temperature of the seat cushion. If the surface temperature is below the temperature set point for the selected low or high heated seat switch position, the module energizes the integral solid-state relay, which supplies battery current to the heating elements. When the sensor input indicates the correct temperature set point has been achieved, the module de-energizes the solid-state relay. The module will continue to cycle the solid-state relay as needed to maintain the temperature set point.

The heated seat system will automatically turn off whenever the ignition switch is turned to any position except ON. If the ignition switch is turned to the OFF position while a heated seat is on, the heated seat will remain off after the engine is restarted until a 2nd row seat heated seat switch is depressed again. This prevents the vehicles battery from being drained by the heated seat system.

The 2nd row heated seat module also controls the heated seat LED indicator lamps, located in both of the 2nd row heated seat switches. The module is programmed to provide self-diagnostics, if a problem with the 2nd row heated seat system is detected. If the module detects faults within the heated seat system, it will provide a visual indication of the failure by flashing the indicator lamps in the appropriate heated seat switch.

The module will automatically turn off the heating elements if it detects an OPEN or HI/LOW short in the sensor circuit, or an OPEN or LOW in the heating element circuit. See the owner's manual in the vehicle glove box for more information on the features, use and operation of the front seat heated seat system.