Tire Pressure Sensor: Description and Operation

GF40.15-P-5126RE Wheel Sensor, Component Description
MODEL 230 as of 1.6.05
with CODE (475) Tire pressure monitor (Siemens)
except CODE (494) USA version
except CODE (498) Japan version
MODEL 230 as of 1.7.05
with CODE (470) Tire pressure monitor (base)
with CODE (494) USA version
except CODE (498) Japan version
MODEL 230 as of 1.7.05
with CODE (475) Tire pressure monitor (Siemens)
with CODE (494) USA version
with CODE (498) Japan version








Design of TPM wheel sensor
Together with the filling valve the TPM wheel sensor forms a compact unit and is installed into the rim like a screw-on valve.
Modifications to the rims are not required.

The following components are located in the housing:
- Pressure sensor
- Temperature sensor
- Transmitter
- Acceleration sensor (radial acceleration)
- Lithium battery for internal power supply

Note: Different TPM systems are produced by Beru and Siemens. This must be taken into account when repairing the TPM system.

Function
Each TPM wheel sensor transmits a data report to the central TPM [RDK] antenna. An individual electronic identification number (ID) is deposited in each TPM wheel sensor. The TPM [RDK] control unit assigns the ID to the wheels fitted to the vehicle (after a learning phase). If an adequate spare wheel with TPM wheel sensor is fitted it is detected and managed after a few minutes' driving.

After a wheel change or after a TPM wheel sensor has been exchanged the new TPM sensor with new ID (e.g. after fitting the spare wheel) is detected as quickly as possible and is monitored as a new ID, even if the TPM [RDK] control unit is still receiving information from the previously used wheel identifier. Wheel identifiers received from other vehicles do not result in incorrect warnings.

Task
The TPM wheel sensors are sensors that transmit the following data by radio signal:
- Absolute pressure
- Temperature of the sensor
- Radial acceleration of the sensor (acceleration is dependent on the wheel speed)
- ID of the sensor

This data is received by the central TPM [RDK] antenna (A2/97) and evaluated by the TPM [RDK] control unit (N88). The TPM wheel sensors contain a battery for transmitting the signals with a service life of 10 years.

Note: The respective TPM wheel sensor must be replaced in the event of a defect in the battery.

The TPM wheel sensors are marked according to national version and transmit their data on different frequencies:
- 315 MHz: recognizable by the frequency indication and an unfilled square symbol
- 433 MHz: recognizable by the frequency indication and square symbol filled with gridlines

The TPM sensors transmit three data telegrams every 60 seconds when driving. These data packets transmit the absolute pressure, the wheel temperature, the acceleration, the ID and status information (manufacturer, frequency, pressure range etc.). The measuring range of the TPM wheel sensor extends from 0 to
5.5 bar (relative pressure).