Tire Pressure Sensor: Description and Operation
GF40.15-P-5126GZ Wheel Sensor, Component Description
MODEL 164
with CODE (475) Tire pressure monitor (Siemens)
except CODE (498) Japan version
MODEL 164.8
with CODE (470) Tire pressure monitor (base)
with CODE (494) USA version
Design
Together with the filling valve (2) the TPM wheel sensors form a compact unit and are fitted in the rims like a screw-on valve.
Modifications to the rims are not required.
The following are located in the housings:
- pressure sensor
- temperature sensor
- transmission stage
- Lithium battery for internal voltage supply
Function
As part of energy management the TPM wheel sensors automatically switch between the following operating modes:
- Energy-saving mode, as long as the component is in store, not fitted to the vehicle.
- As long as no relevant pressure change is detected, every 55 s data reports with identification numbers specific to the electronics unit are transmitted for system monitoring and for detecting very slow pressure changes. The wheel electronics unit identifier (ID) is used to assign the wheels installed on the vehicle.
- The measurement rate and transmission rate is increased (0.8 seconds) if a rapid pressure change has been detected at a wheel. The TPM control unit (N88) is thus provided with a number of measured values within a short period of time, allowing reliable evaluation of the pressure change.
- Switching off the measurement electronics and transmission electronics at temperatures > 120°C, as reliable recording of data and data transfer is not guaranteed in this driving condition. The measurement electronics and transmission electronics are switched on again automatically when cooled down <100°C.
Energy management
Due to the finite space the battery size and as a result the battery capacity is limited. An intelligent energy management system provides an estimated service life of approx. 7 years with a single battery.
Note: The respective TPM wheel sensor must be replaced in the event of a defect in the battery.