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Home >> Lexus >> 2008 >> IS 250 RWD, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 43 (Tire Pressure Warning System) >> Tire Pressure Warning System >> System Description

System Description

WARNING: This page is about a different car, the 2008 Lexus IS F. However, it is still accessible from the selected car via links, so may be relevant.
  1. DESCRIPTION OF SYSTEM 
    1. Each tire pressure warning valve and transmitter is equipped with a tire pressure sensor and a transmitter and is installed in a tire and wheel assembly. The sensor measures the tire pressure The measured value and transmitter IDs are transmitted to the tire pressure warning antenna on the body as radio waves and then sent to the tire pressure warning ECU and receiver from the tire pressure warning antenna. If the transmitter ID has already been registered, the ECU compares the measured air pressure value with the standard value. When the value is less than the standard value registered in the tire pressure warning ECU and receiver, the tire pressure warning light and master warning light on the combination meter come on and "LOW TIRE" will appear on the multi-information display.
      • Tire pressure warning system transmitters with a different shape are provided for aluminum wheels (They are not interchangeable with other wheels)
        Fig 1: Identifying Tire Pressure Warning Valve And Transmitter
        G05752447Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. INITIAL CHECK 
    1. After the engine switch is turned on (IG), the tire pressure warning light comes on for 3 seconds and then goes off.

      HINT.

      If the tire pressure warning light does not come on for 3 seconds, troubleshoot the tire pressure warning light circuit

      TROUBLE AREA CHART

      Trouble Area Proceed to
      Tire pressure warning light circuit TIRE PRESSURE WARNING LIGHT CIRCUIT 
      Fig 2: Identifying Tire Pressure Warning Valve And Transmitter
      G05752448Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. WHEN TIRE PRESSURE WARNING LIGHT IS LIT 
    1. When the tire pressure warning light does not go off, or comes on while driving, check the tire pressure If the tire pressure warning light comes on within several hours after adjusting the tire pressure, the tire may have a slow air leak If the tire pressure warning light comes on even soon after adjusting the tire pressure, selection of the tire pressure warning switch (satellite switch) "MAIN" / "2nd" may be incorrect
    2. Under the following conditions, the system may not function properly
      • Areas, facilities or devices that use similar radio frequencies are located in the vicinity of the vehicle
      • Devices using similar radio frequencies are used in the vehicle
      • Large amounts snow or ice are stuck to the vehicle, especially on the wheels and around the wheel housings
      • A transmitter battery is depleted
      • Tires and wheels without tire pressure warning valve and transmitters are used.
      • Snow tires or tire chains are used.
      • The registered set of the tires and wheels does not correspond to the selection of the tire pressure warning select switch.
      • If wheels other than the specified ones are used, radio waves transmitted from the tire pressure warning valve and transmitter may be affected.
      • A type of film that affects radio waves is attached to the windows.
      • Depending on the tire type, the tire pressure warning valve and transmitter may not function properly even if the specified wheels are used.
      • The system may not function properly unless it is initialized with the tire pressures at the specified values.
      • The tire pressure is abnormally high (absolute pressure 600 kPa (6 0 kgf/cm2 , 87 psi) or more, relative pressure 500 kPa (5 0 kgf/cm2 , 73 psi) or more)
    3. The average useful life of the grommet of the tire pressure warning valve and transmitter is approximately 10 years, at which time it must be replaced
      NOTE: Always use a new grommet, washer and nut when installing the tire pressure warning valve and transmitter.
    4. After removing and installing the ECU or a transmitter, check that no DTCs are output.
  4. FUNCTION OF COMPONENTS 
    FUNCTION OF COMPONENTS

    Component Function
    Tire pressure warning valve and transmitter Combined as a single unit with an air valve, this component measures tire pressure and temperature and transmits an ID number for measurement value and identification Contains a built in battery
    Tire pressure warning antenna Receives and transmits a necessary signal from the transmitter to the tire pressure warning ECU and receiver
    Tire pressure warning ECU and receiver Receives a signal from the receiver and identifies it as the vehicle's own signal If the measurement value is equal to or lower than the specified value, this component transmits a signal so that the air pressure warning light on the combination meter comes on
    Tire pressure warning light Located in the combination meter, it informs the driver of a decrease in the tire pressure or a system malfunction
    Satellite switch Includes the tire pressure warning reset switch and select switch functions Initialization can be performed by selecting the tire pressure warning reset switch mode on the multi-information display and operating the satellite switches Also, the tires can be selected by selecting the tire select switch mode and operating the satellite switches
    Tire pressure warning reset switch (satellite switch) Enters initialization mode for tire or wheel replacement, or tire pressure warning ECU and receiver replacement
    HINT
    The satellite switches include the tire pressure warning reset switch function
    Tire pressure warning select switch (satellite switch) When 2 sets of IDs are registered in the tire pressure warning ECU and receiver, either of the sets can be selected by changing the switch between "MAIN and "2nd"
    HINT
    The satellite switches include the tire pressure warning select switch function
  5. TIRE PRESSURE WARNING RESET SWITCH (SATELLITE SWITCH) 
    • By operating the tire pressure warning reset switch, the tire pressure warning ECU and receiver can be set to issue a warning at an inflation pressure that corresponds to the type of tires

      Therefore, the dealer must set the warning threshold to the proper value in order to comply with the local regulations.

    • Operate the tire pressure warning reset switch only after the inflation pressures of 4 tires have been adjusted on the vehicle.
    • To initialize the system, press and hold the tire pressure warning reset switch for 3 seconds or longer with the engine switch on (IG). When the system receives the initialization signal, the warning light blinks 3 times (1 second on, 1 second off).
    • During initialization, the tire pressure warning valve and transmitter measures the inflation pressure of the tires, and registers the signals that are transmitted into the tire pressure warning ECU and receiver at a frequency of once per minute. The initialization process is completed when signals from the 4 tires have been received.
    • Initialization is usually completed in 2 or 3 minutes.
  6. TIRE PRESSURE WARNING SELECT SWITCH (SATELLITE SWITCH) 
    • This switch is installed at the base of the driver side instrument panel.
    • The ECU can be used to register 2 sets of transmitter IDs, and can select one or the other using the tire pressure warning select switch Consequently, there is no need to register the IDs again each time the tire and wheels are changed.
    • Make sure ID registration is performed by your car dealer
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