Sienna 1998-1999

Tire Pressure Monitor System



Removal & Installation

The TPMS display is an integral part of the instrument panel and cannot be serviced separately.

Pressure Monitor


When the tire pressure warning light comes on, immediately check the tire pressure and adjust it to the specified value. (The tire pressure warning light will come on after blinking for 1 minute if there is an open in the tire pressure warning light circuit.).

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Fig. Cold tire inflation pressure

Check the full-size spare tire as well since this system monitors pressure of all tires including the full-size spare tire.

When the tire pressure warning light blinks (comes on after blinking for 1 minute), there is a malfunction in the system. Check for DTCs.

It is necessary to register the transmitter ID in the tire pressure warning ECU after replacing the tire pressure warning valve and transmitter and/or tire pressure warning ECU

Initialize the tire pressure warning system after any of the following is performed: Replacing the tire pressure warning ECU or the tire pressure warning valve and transmitter. Installing tire(s) which require different tire pressure. Rotating tires on vehicles with differing front and rear tire inflation pressures. Changing the tire inflation pressure by changing traveling speed or load weight, etc.

The tire pressure warning system will not operate properly if it is not initialized.

Precautions about the tire pressure: The tire pressures decrease naturally. In winter, tire pressures may decrease due to low ambient temperatures (tire pressure decreases by approximately 1.45 psi (0.2 kgf/cm 2, 10 kPa) for every 50°F (10°C) drop in the ambient temperature). Therefore, the tire pressure warning is more likely to operate if the tire pressures are not adjusted appropriately. If the daily temperature variation is large, pressurize the tires high so that the tire pressures are suitable under cold conditions. Incorrect tire pressure warning operation becomes less likely.

Fail-safe function: When a system malfunction occurs in the tire pressure warning system, the tire pressure warning light blinks (comes on after blinking for 1 minute) and informs the driver of the system failure. The result of this diagnosis is stored in the tire pressure warning ECU.

After repairs, confirm that the actual tire pressures are displayed in the Data List.

Receiver/Control Unit

Removal & Installation

The TPMS control unit is an integral part of the ABS/ESC brake actuator control unit assembly and is not serviced separately.


Removal & Installation

Toyota uses an indirect system for determining tire pressure. Indirect systems use software in combination with wheel speed sensors for anti-lock braking systems, and electronic stability control systems. They do not use physical pressure sensors (transmitters), but measure "apparent" air pressure, by monitoring individual wheel rotational speeds. An under-inflated tire has a slightly smaller diameter than a correctly inflated tire and therefore has to rotate at a higher velocity to cover the same distance as a correctly inflated tire.