Tire Pressure Sensor: Service and Repair
WM 443219 Removing and installing wheel electronics
Removing wheel electronics
General information on wheel electronics
The Tyre Pressure Monitoring (TPM) system is designed to constantly monitor the tyre pressure when the vehicle is moving and stationary. One set of electronics -A- per tyre is mounted in the rim well base. These measure tyre 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 tyre pressure needs to be adjusted.
There are various versions of the wheel electronics -A-. In the case of the Cayenne, versions with amplified transmitting power are used. These transmit in a high frequency range of:
- 433 MHz or 315 MHz.
The following points can be used as distinguishing characteristics:
- The labelling - 433 MHz or 315 MHz
- And/or the colour (dark grey - 433 MHz; light grey - 315 MHz).
- The part number
- No stars on the left and right of the slot
2nd generation wheel electronics
Removing wheel electronics
Information
- For vehicles with a tyre pressure monitoring system, the valve and wheel electronics are only replaced in exceptional cases! The following points can make replacement necessary!
Valve complete with screw -1 to 7- has to be replaced if:
- The wheel electronics are removed
- The self-locking -1- fastening screw is loose
- The bead seat sealing ring -6- is porous or damaged
- The valve body -7- is bent
- The union nut -4- is loose.
The wheel electronics -A- must be replaced if:
2nd generation wheel electronics
- 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 sealant (tyre sealing liquid) has been used
- The service life of the battery has expired
- There is a fault within the wheel electronics.
After removal of the tyre, the wheel electronics -A- can be seen at the valve in the outer rim well base.
Fitted wheel electronics, by way of example
1. Release wheel electronics from valve using a Torx socket screwdriver T 20 (if necessary, counter with a suitable assembly pin, e.g. steel pin dia. approx. 1.8 mm in bore at valve foot) and remove it.
2. Then unscrew union nut and remove valve.
Installing
Installing wheel electronics
When replacing the wheel electronics unit, always use a completely new valve and a new fastening screw!
The tightening torque for wheel electronics unit/valve is 4 Nm/3 ftlb. (+/- 0.5 Nm/0.5 ftlb.)!
The wheel electronics unit must not come into contact with the tyre fitting paste or solvent!
Every tyre set or wheel change must be communicated to the control unit. In particular, this is necessary when wheel positions have been interchanged. For this purpose, in the instrument cluster under main menu > Tyre pressure > Adjustments, always select the tyre type and tyre size. During driving, the control unit then learns the wheel positions again.
1. Install the wheel electronics unit loosely at the valve (do not tighten) and position in valve bore together with valve and bead seat sealing ring.
Information
Carry out the tightening procedure to the specified torque for the valve in the rim once only. Remove the assembly pin after fitting the valve. The tyre can be damaged if the assembly pin is left in the valve.
Information
Counter the valve with assembly pin.
- Twisting the valve-stem seal is possible which can cause damage.
- Removing the valve again is made easier.
2. Fit washer, chamfered on both sides, and screw on union nut until it is seated correctly. Visibly twist bore at valve foot and block with suitable assembly pin. The tightening torque is 4 Nm/3 ftlb. (+/- 0.5 Nm/0.5 ftlb.).
3. Push wheel electronics -A- slightly into rim well base (this adjusts the angle of inclination of valve to wheel electronics).
Fitted wheel electronics, by way of example
4. Carefully tighten self-locking (Torx) fastening screw T 20 to 4 Nm/3 ftlb. +/- (0.5 Nm/0.5 ftlb.). The wheel electronics unit should now be lying evenly against the rim.