TIRE PRESSURE MONITORING: TIRE PRESSURE WARNING SYSTEM: SYSTEM DESCRIPTION (2008 LX570)

SYSTEM DESCRIPTION

1. DESCRIPTION OF SYSTEM

(a) Each tire pressure warning valve and transmitter is equipped with a tire pressure sensor and transmitter and is installed in each tire wheel. The sensor measures the tire pressure. The measured value and transmitter ID are transmitted to the tire pressure warning antenna and receiver on the body as radio waves and then sent to the tire pressure warning ECU from the tire pressure warning antenna and receiver. If the transmitter ID has already been registered, the ECU compares the measured tire pressure value with the standard value. When the value is less than the standard value registered in the tire pressure warning ECU, the warning light on the combination meter turns on.

When it is necessary to change the tire pressure setting, use the tire pressure warning reset switch to initialize the system.

2. INITIAL CHECK

(a) After the engine switch is turned on (IG), the tire pressure warning light turns on for 3 seconds and then turns off.

HINT:

If the warning light does not turn on for 3 seconds, troubleshoot the pressure warning light circuit.

Trouble Area	Proceed to
Tire pressure warning light circuit

(a) When the tire pressure warning light does not go off, or when it turns on during driving, check the tire pressure. If the tire pressure warning light turns on within several hours after adjusting the tire pressure, the tire may have a slow air leak.

Tires without a tire pressure warning valve and transmitter are used.
A tire pressure warning valve and transmitter ID is not registered in the ECU.
The tire pressure is abnormally high (absolute pressure: 600 kPa (6.1 kgf/cm², 87 psi) or higher; relative pressure: 500 kPa (5.1 kgf/cm², 73 psi) or higher).
The battery of the tire pressure warning valve and transmitter has been depleted (battery life: 10 years).

Facilities or devices that use similar radio frequencies are located in the vicinity of the vehicle.
A radio device of similar frequency is used in the vehicle.
A type of film that affects radio waves is attached to the windows.
A large amount of snow or ice is stuck to the vehicle, especially onto the wheels and around the wheel houses.
Any wheels other than the specified ones are used.
Tire chains are used.
A large metallic object which can interfere with signal reception is put in the luggage room.
The spare tire is not within the receivable range of the tire pressure warning antenna and receiver.

(d) If a tire pressure warning valve and transmitter is removed from a wheel, replace the grommet.

(e) After removing and installing the ECU or a sensor, check for a diagnostic trouble code and verify that it is a normal code.

Components	Function
Tire pressure warning valve and transmitter	Combined as a single unit with a disc wheel air valve, it measures tire pressure and temperature and transmits an ID number with the measurement values for identification. Has a built-in battery.
Tire pressure warning antenna and receiver	Receives signals from a transmitter and sends the signals to the tire pressure warning ECU.
Tire pressure warning ECU	Determines the current status based on the signals from the receiver, and displays the status on the combination meter.
Tire pressure warning light	Located in the combination meter, it informs the driver of lowered tire pressure and system failure.
Tire pressure warning reset switch	Enters initialization mode for tire or wheel replacement.

Components

Function

Tire pressure warning valve and transmitter

Combined as a single unit with a disc wheel air valve, it measures tire pressure and temperature and transmits an ID number with the measurement values for identification. Has a built-in battery.

Tire pressure warning antenna and receiver

Receives signals from a transmitter and sends the signals to the tire pressure warning ECU.

Tire pressure warning ECU

Determines the current status based on the signals from the receiver, and displays the status on the combination meter.

Tire pressure warning light

Located in the combination meter, it informs the driver of lowered tire pressure and system failure.

Tire pressure warning reset switch

Enters initialization mode for tire or wheel replacement.

By operating the tire pressure warning reset switch, the tire pressure warning ECU 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 local regulations.
Operate the tire pressure warning reset switch only after the inflation pressures of all tires (including the spare tire) have been adjusted on the vehicle.
To initialize the system, press and hold the tire pressure warning reset switch for 3 seconds or more 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 transmitters measure the inflation pressure of the tires, and register the signals that are transmitted into the tire pressure warning ECU at a frequency of once per minute. The initialization process is completed when signals from all tires (including the spare tire) have been received.