Tire Pressure Warning System System Description

The tire pressure warning system warns the driver when the tire pressure has decreased in order to decrease CO2 emissions and enhance safety.

for FMVSS138 Type:
The tire pressure warning system illuminates the tire pressure warning light to warn the driver when the following condition is met:

1. Due to the operation of the tire pressure warning reset switch, the tire pressure drops to approximately 75% or less of the tire pressure set during system initialization.
   

for ECE-R64 Type:
The tire pressure warning system illuminates the tire pressure warning light to warn the driver when any of the following conditions are met:

1. Due to the operation of the tire pressure warning reset switch, the tire pressure drops to approximately 80% or less of the tire pressure set during system initialization.
   
2. The tire pressure drastically decreases (approximately 20 kPa (0.2 kgf/cm², 2.9 psi) or more within several minutes) to approximately 80% or less of the tire pressure* when the tires are warmed.
   *: If initialization is performed and the vehicle is driven for a certain period of time, the tire pressure set during system initialization is adjusted and set to the tire pressure when the tires are warmed from the driving conditions.
   

NOTICE:

If the tire pressure is decreased approximately 20 kPa (0.2 kgf/cm², 2.9 psi) or more in order to adjust the tire pressure, even if the adjusted tire pressure is 80% or more than the tire pressure set during system initialization, the tire pressure warning light may illuminate if the tire pressure drops below 80% of the tire pressure set when the tires are warmed. In this case, perform initialization again.

The tire pressure warning ECU and receiver receives the transmitter ID, temperature and tire pressure information from the tire pressure warning valve and transmitters shown in the following illustration. This information is used to determine when the pressure in one of the tires has dropped.

The tire inflation pressure display function displays the position and pressure of each tire on the multi-information display. The previous tire positions and pressures will be displayed until they are automatically updated.

The tire position can be identified using either of the following methods:

1. Using GTS:
   Using the GTS, manually enter the tire position for each transmitter ID.
   

2. Not Using GTS:
   Perform initialization to clear the existing tire position information, then drive the vehicle at 40 km/h (25 mph) or more for 10 minutes or more until each tire position is automatically identified.
   

When tires and wheels are replaced, always ensure that each transmitter ID is correctly registered.

When one or more of the tire pressure warning valve and transmitters or the tire pressure warning ECU and receiver is replaced, the transmitter IDs for all of the tire pressure warning valve and transmitters must be re-registered. Before registering the transmitter ID of a new tire pressure warning valve and transmitter, check the Data List and record all of the transmitter IDs that are already registered.

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 fitted to the vehicle. Therefore, the warning threshold must be set 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 have been adjusted on the vehicle.

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 and receiver at a frequency of about once per minute. The initialization process is completed when signals from all tires have been received.

Perform initialization in the following cases:

1. Before delivery of a new vehicle.
   

2. After replacement of the tire pressure warning ECU and receiver*.
   

3. After replacement of a tire pressure warning valve and transmitter*.
   

4. When the specified tire pressure changes due to the use of a different size or type of tire.
   

5. When the specified tire pressure changes due to a change in the vehicle load, the speed range that the vehicle will be used in, etc.
   

6. When a tire rotation is performed and the specified tire pressures are different for the front and rear of the vehicle.
   

   HINT:

   *: Perform initialization after the transmitter ID registration is completed.

By designating the ID registration location, it is possible to register transmitter IDs for both the main and 2nd set of tires.

When IDs are registered for both the main transmitter side and sub-transmitter (2nd) side, it is possible to switch between the main transmitter side and sub-transmitter (2nd) side by operating the tire pressure warning reset switch (Click here).

NOTICE:

Be careful, as the method to perform ID switching differs from the method to perform initialization.

When reading the status for a registered ID, it is only possible to read the ID information for the selected set of tires.

HINT:

In order to read the IDs registered for the main tire set, it is necessary to set the ID selection setting to "Main". Likewise, it is necessary to set the ID selection setting to "2nd" in order to read IDs registered for the 2nd set of tires.