Description of Components

Description of components
Tire Pressure Monitoring Control Module -J502-
The tire pressure monitoring system control module evaluates the radio signals received from the tire pressure monitoring system antennas, prioritizes them and relays corresponding information to the instrument cluster. There, corresponding messages are displayed on the driver information system (DIS). Communication with the vehicle periphery is accomplished via the CAN comfort databus. Prioritization of system messages is performed by means of evaluation of various limit values and of the pressure drop as a function of time (pressure-drop gradient). The control module is located in the left-hand stowing compartment of the boot.

Tire pressure sensors -G222- to -G225-
The pressure sensor registers instantaneous tire pressure (absolute pressure), which is then transmitted to the tire pressure monitoring system control module for evaluation. The sensor is screw-mounted on the metal valve and can be re-used when wheels or hubs are changed.

The following components are integrated into the sensor: Transmitter antenna, pressure and temperature sensor, control/instrumentation electronics, and a battery. The temperature signal is used for correction of the temperature-dependent changes in tire pressure, and for diagnosis purposes. The sensor discontinues radio transmission when a defined temperature threshold is exceeded.

Each sensor has its own individual identification code (ID code) in the form of a ten-digit number. The ID codes are included in the data telegrams from the sensors and are transmitted sequentially. They are used for assignment of the sensors to the vehicle. Continuous comparison of the I D codes received and stored takes place. This prevents "foreign sensors" located within radio range interfering with the system.

Two different carrier frequencies are used for radio transmission depending on local vehicle version. A carrier frequency of 433 M H z is approved for most countries, while a carrier frequency of 315 MHz is used for certain others (e.g. the USA).

Tire pressure monitoring system antennas -R59- to -R62-
The tire pressure monitoring system antennas receive the radio signals from the tire pressure sensors and relay them to control module -J502for further processing. The four antennas are installed at the front left front right, rear left and rear right in the wheel housings behind the wheel housing liners. They are connected to control module -J502- by means of high-frequency antenna cables. Malfunctioning antenna cables must not be repaired, in order that there is no interference in high-frequency transmission. Damaged antenna cables must be completely replaced (new cable set).