From the manual...........

oke:
Flat Tire Monitor
The concept
As you drive, the Flat Tire Monitor keeps track of pressure levels in all four tires. The system alerts you whenever the inflation pressure of a tire falls significantly below the pressure of another tire.
In the event of tire pressure loss, the rolling radius of the tire changes, thereby affecting therotational speed of the wheels. This change is
detected, and a flat tire warning is issued to the
driver.
System requirements
To ensure a reliable flat tire warning, the system must be initialized with the correct tire inflation pressures. Each time you correct the pressure in a tire, or change a wheel or tire, the system must be re-initialized.
System limitations
The Flat Tire Monitor cannot provide you with advance warning of sudden and severe tire damage caused by external factors and does not detect the balanced and very gradual pressure loss that takes place in all four tires over an extended period of time. The system could issue a false warning or function in a delayed manner in the following situations:
> System was not initialized
> You are driving on a snow-covered or slippery
road surface
> Performance-oriented driving: slip at the
drive wheels, high levels of lateral acceleration
> You are driving with snow chains.
Initializing the system
The initialization is completed while you are driving, and can be interrupted at any time. Initialization is automatically continued when you continue driving. When driving with snow chains, do not initialize
the system.
1. Start the engine, but do not drive off
2. Press the button as long as you need to until
the yellow indicator lamp in the instrument
cluster lights up for a few seconds
3. Drive off.
Initialization is completed during the drive, without any feedback issued.