Chassis
Page 4.12
Central Antenna
The digital central antenna (reception frequency 315) is secured close
to the center of the underside of the left side member under the vehicle
and is protected from stone damage by the sill cover. The signals
received from the wheel electronics units are digitalized in the antenna
and forwarded to the control unit via two normal lines (LIN bus). The
digital antenna has an integrated self-diagnosis facility. This means that
when a fault is detected, it is stored in the control unit fault memory and
displayed on the PIWIS Tester.
Wheel Electronics
The wheel electronics unit (wheel transmitter 315 MHz) is screwed to
the rim using the wheel valve.
The wheel electronics unit comprises the following components:
• Pressure sensor,
• temperature sensor,
• roll switch,
• measuring and control electronics,
• receiver and transmitter,
• and a battery.
The wheel electronics unit can be triggered and receives send requests
from the TPM control unit via four triggers. This means that the antenna
always receives only one data protocol and this comes from the wheel
electronics unit that received the request to send. This gives the system
added protection against interference affecting other antennas. Higher
transmission power is used due to the longer radio link to the central
antenna.
The roll switch detects whether the wheel is stationary or turning. This
information is used either to start a triggered learning process for a
moving wheel or to switch off the wheel electronics unit when the wheel
has been stationary for a long time.
To avoid confusion with 1st generation wheel electronics, the new wheel
electronics unit can be identified by the modified shape of the housing
and the small air filter. A modified data protocol ensures that the wheel
electronics unit will not be detected if incorrect part is installed and this
is stored as a fault in the fault memory.
Note
The central antenna is designed to pick up
various frequencies (433 RoW/315 MHz
USA/Canada).
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