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

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 air pressure value with the specified value. When the value is less than the specified value registered in the tire pressure warning ECU, the warning light on the combination meter turns on.

The tire pressure warning reset switch addresses the differences in the standard pressure of the tire.

2. INITIAL CHECK

(a) After the ignition switch is turned to ON, 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.

If tires not equipped with the tire pressure warning valves and transmitters are used.
If the ID code on the tire pressure warning valves and transmitters is not registered in the tire pressure warning ECU.
If the tire pressure warning valve and transmitter battery voltage drops (battery life: 10 years).

If electronic devices or facilities using similar radio wave frequencies are nearby.
If a radio set at similar frequencies is in used in the vehicle.
If a window tint that affects the radio wave signal is installed.
If there is a lot of snow or ice on the vehicle, in particular around the wheels or wheel housings.
If non-genuine wheel are used.
If tire chains are used.

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

Component	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 a transmitter ID for measurement values and 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	Receives the signal from the receiver and identifies it as the vehicle's own signal. If the measured value is equal to or lower than the specified value, it transmits a signal so that the tire pressure warning light on the combination meter turns on.
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 the initialization mode for change of the standard pressure.

Component

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 a transmitter ID for measurement values and 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

Receives the signal from the receiver and identifies it as the vehicle's own signal. If the measured value is equal to or lower than the specified value, it transmits a signal so that the tire pressure warning light on the combination meter turns on.

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 the initialization mode for change of the standard pressure.

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 standard pressure 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 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 ignition switch ON. 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 at a frequency of once per 3 minutes. The initialization process is completed when signals from all tires have been received. It takes several minutes.