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System Description

  1. HEATED STEERING WHEEL SYSTEM 
    1. The heated steering wheel heats the steering wheel when the heated steering wheel switch on the outer mirror switch is operated.
    2. The heated steering wheel uses a thermistor inside of the steering wheel to detect the heater temperature and maintain the set temperature.
    3. The heated steering wheel's timer function turns off the heater after a predetermined period of time.
  2. HEATER CONTROLLER SYSTEM 
    1. Operation description
      Fig 1: Heater Controller System - Operation Description Flow Diagram
      G04950156Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      1. When the engine switch is on (IG), pressing the heated heated steering wheel controller's momentary switch on the outer mirror switch illuminates the LED and current is output from the steering controller to the heater of the heated steering wheel. Pressing the momentary switch again turns off the LED and stops the current from being output.
      2. A thermostat is installed in the steering wheel as a safety mechanism.
      3. The heated steering wheel switch's LED will blink at 0.3 second intervals when either of the following occurs: 1) an open or short in the steering wheel's thermistor continues for 2 seconds or more; or 2) the outer mirror switch's momentary switch is pressed continuously for 10 seconds or more.
      4. If the normal condition is restored for 2 seconds or more, the previous operation before the malfunction occurred continues. However, regardless of if a malfunction is detected and the malfunction operation is occurring, and regardless of if the normal condition is restored and the system is operating normally, the timer will turn off the heater 30 minutes after the switch was first turned on.
    2. Signal input / output description
      Fig 2: Heater Controller System - Signal Input / Output Description Flow Diagram
      G04950157Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      SIGNAL INPUT / OUTPUT DESCRIPTION

      Signal Signal Name Function Signal Type
      Input Thermistor input Input of voltage corresponding to heater temperature Analog input
      Input Temperature setting input Input of voltage corresponding to temperature setting Analog input
      Input Operating switch input Input of power circuit's latch operation estimate signal LOW / HI input
      Output LED output Output of LED LOW / HI input
      Output Heater output Output of heater LOW / HI input
      Output Latch output Power circuit maintenance LOW / HI input
    3. Safety function
      SAFETY FUNCTION REFERENCE

      Content Operation
      When thermistor trouble is detected Heater off
      When overheating (150°C (302°F)) of controller is detected Heater off
      When over voltage (60 V) is detected Heater off
      When under voltage (6 V) is detected Heater off
      OFF timer (30 min.) After preset time of timer passes, heater off
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