WARNING
It is the driver's responsibility to set the tire pressure to the recommended cold tire pressure. Underinflated tires affect the ability to steer or brake the vehicle. You might lose control over the vehicle.

When you restart the tire pressure monitor, all existing warning messages are deleted and the warning lamps go out. The monitor uses the currently set tire pressures as the reference values for monitoring. In most cases, the tire pressure monitoring system recognizes the new reference values automatically.

However, you can also define reference values manually as described here:
  Set the tire pressure to the value recommended for the corresponding driving situation on the Tire and Loading Information placard on the driver's side B-pillar.
Additional tire pressure values for driving at high speeds or with heavy loads can be found in the tire pressure table on the inside of the fuel filler flap.
  Make sure that the tire pressure is correct on all four wheels.
  Make sure that the SmartKey is in position 2 in the ignition lock.
  Press the or button on the steering wheel to select the Service menu.
  Press the or button to select Tire Pressure.
  Press the button.
The multifunction display shows the current tire pressure of the individual tires or the Tire pressures will be displayed after driving a few minutes message.
  Press the button.
The Use Current Pressures as New Reference Values message appears in the multifunction display.

If you wish to confirm the restart:

  Press the button.
The Tire Press. Monitor Restarted message appears in the multifunction display.
After driving for a few minutes, the system checks whether the current tire pressures are within the specified range. The new tire pressures are then accepted as reference values and monitored.

If you wish to cancel the restart:

  Press the button.
The tire pressure values stored at the last restart will continue to be monitored.