Tire Monitoring System: Description and Operation

Tire Pressure Monitoring System Description

Tire Pressure Monitoring System (TPMS) is controlled by keyless start control module and works according to the following process.

TPMS monitors air pressure in each tire except spare tire. It consists of low tire pressure warning light (9), tire pressure sensors (1) (2) (3) (4), keyless entry / TPMS receiver (6) and keyless start control module (7).

As a tire revolves (at vehicle speed of approximately 25 km/h (16 mph) or more), tire pressure sensor installed to each wheel transmits tire pressure data through keyless entry / TPMS receiver to keyless start control module. When tire pressure is lower than the standard value in the module, keyless start control module makes low tire pressure warning light light up to warn the driver that tire pressure has decreased. Also, when any fault is detected in TPMS, it makes low tire pressure warning light blink for 75 seconds and then the warning light remains lit to warn the driver that there is a fault in the system.

Operation of tire pressure sensor, keyless entry / TPMS receiver, keyless start control module and low tire pressure warning light is described below.










Tire Pressure Sensor

Tire pressure sensor consists of a pressure sensor, acceleration sensor, control section, transmitter/receiver, battery and air valve.

Each tire pressure sensor is assigned an individual ID code. Tire pressure detected by the tire pressure sensor, along with the ID code and battery status, is transmitted to the keyless entry / TPMS receiver on the radio wave. As the tire revolves at a vehicle speed of approximately 25 km/h (16 mph) or more, the pressure sensor transmits data at 64-second intervals to keyless entry / TPMS receiver (active mode). However, when the acceleration sensor does not detect wheel rotation with the vehicle speed less than approximately 5 km/h (3 mph), data is sent to keyless entry / TPMS receiver at 13-hour intervals so as to prevent battery power consumption (pause mode).

Keyless Entry / TPMS Receiver

The function of TPMS receiver is included in keyless entry receiver.

Keyless entry / TPMS receiver receives data from tire pressure sensor, converts it from an analog signal to digital signal and transmits it to keyless start control module.

Keyless Start Control Module and Low Tire Pressure Warning Light

Keyless start control module receives signals from 4 tire pressure sensors, identifies data by the ID code of each tire pressure sensor and uses the identified data to compare air pressure in each tire with the specified value. When tire pressure is judged to be lower than the specified value (205 kPa (29.7 psi)), keyless start control module makes low tire pressure warning light in the combination meter light up and stores DTC in its memory. Also, when a fault in the system is detected, keyless start control module makes low tire pressure warning light blink for 75 seconds and then the warning light remains lit, and stores the DTC in memory.

NOTE:

Four ID codes of tire pressure sensor can be registered in keyless start control module. Therefore, when wheel with tire equipped with any other sensor is used as a running wheel, ID codes of all tire pressure sensors installed to 4 tires must be re-registered. When vehicle is driven without re-registration of the ID codes, keyless start control module detects faulty condition of the system and makes low tire pressure warning light illuminate after 75-second blinks. For the procedure to register the ID codes of tire pressure sensors in keyless start control module, refer to Registration Procedure for Tire Pressure Sensor ID Code Registration Procedure for Tire Pressure Sensor ID Code.

Vehicle Speed Signal

Keyless start control module uses the vehicle speed signal from ECM to judge whether tire pressure sensor is operating properly.