General Information On Wheel Electronics

The Tyre Pressure Monitoring (TPM) system is designed to constantly monitor the tire pressure when the vehicle is moving and stationary. One wheel electronics unit -8-  per tire is mounted in the rim well base. These measure tire pressure and temperature at regular intervals and transfer the values to a central control unit via a high-frequency route. The control unit evaluates the information and transfers the data to the instrument cluster if required. In this way, the driver is warned and informed if the tire pressure needs to be adjusted.

There are two types of wheel electronics -8-  . Wheel electronics units with amplified transmitting power are used on the Cayenne. These transmit in the high-frequency range of:

• 433 MHz or 315 MHz.

The following points can be used as distinguishing features: 

• The labelling - 433 MHz or 315 MHz.
• The color (dark grey - 433 MHz; light grey - 315 MHz).
• The part number.
• No stars on the left and right of the slot.

The valve must be replaced complete with screw -1, 3, 4- if: 

• The wheel electronics unit is removed
• The self-locking fastening screw -1-  is loose
• The valve body -5-  is bent
• The union nut -7-  is loose.

The wheel electronics unit -2- must be replaced if: 

• The housing is visibly deformed
• The filter surface (round, porous section on back of wheel electronics) is so badly soiled that it can no longer be cleaned by wiping
• Tyre sealing compound (tire sealing liquid) has been used
• The service life of the battery is exceeded
• There is a fault inside the wheel electronics unit.

1. Self-locking (Torx) fastening screw
2. Wheel electronics
3. Valve, complete (No. 5 to No. 7)
4. Valve cap
5. Valve body with valve insert
6. Double chamfered washer
7. Union nut
8. Wheel electronics assembled
Fig 1: Identifying 3rd Generation Wheel Electronics
Courtesy of PORSCHE CARS NORTH AMERICA, INC.