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Pressure sensor, tyre pressure (754)

Pressure sensor, tyre pressure (754)

Location

The pressure sensor is located in the tyre valve.


Main function

The sensor sends information on tyre pressure, temperature and rotation direction to the control module, which in turn informs the driver if a tyre has air pressure that is too low.

Type

The tyre pressure sensor is an integrated sensor with transmitter, battery and valve. It consists of a plastic housing, with an electronic unit, which is cast into an aluminium housing with a valve. Fitted on the valve are a conical seal and a crown nut, used to fit the valve in the edge of the rim. The sensor weighs approximately 38 g.

Connection

Fitted in the sensor is a 3V (500 mAh) lithium battery, which is activated when speed exceeds 20 km/h. The battery is not replaceable.

Function

The pressure sensor measures pressure and temperature in the tyre and also its rotation direction. The temperature value is only used in certain markets. Each sensor has a unique code, which is sent with each block of information. The sensors are fitted in special Saab wheel rims. Normally the sensor measures every 10 seconds and transmits once per minute. If the pressure decreases by more than 0.08 bar from the latest measurement then a new transmission takes place after 10 seconds.

When the battery voltage is too low the control module sends a system fault message on the I-bus.