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 system is designed to constantly monitor the tyre pressure during driving and when the vehicle is stopped. 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 two versions of the wheel electronics -A-. Wheel electronics with normal transmission power are used on the Boxster (987) (while the version on the Cayenne has amplified transmission power). These transmit on a high frequency range of:
- 433 MHz or 315 MHz (while special wheel electronics with a frequency of 315 MHz are used for Japan).
The following points can be used as distinguishing characteristics:
- the labelling, 433 MHz or 315 MHz
- the part number
- without 8 stars (figure shows 8 stars, four on the left and right of the slot respectively, wheel electronics with amplified transmission power on the Cayenne)
- special wheel electronics - 315 MHz for Japan: marking with 14 diagonal lines
- and/or the colour (black = 433 MHz/grey = 315 MHz).
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 unit is 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 unit -A- must be replaced if:
- The housing is visibly deformed
- The filter surface (rectangular or round, porous section on back of wheel electronics unit) 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 unit.
After removal of the tyre, the wheel electronics unit -A- can be seen at the valve in the outer rim well base.
1. Release the wheel electronics unit 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 wheel electronics
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
When coating the rim with tyre mounting paste, make sure not to coat the area around the wheel electronics. Tyre mounting paste must not get under the wheel electronics or into the filter area. This can damage the wheel electronics.
When replacing the wheel electronics, always use a completely new valve and a new fastening screw!
The tightening torque for the wheel electronics/valve is 4 Nm (+/- 0.5 Nm)/3 ftlb. (+/- 0.5 ftlb.)!
Every tyre set or wheel change must be communicated to the control unit. In particular, this includes the case where wheel positions have been interchanged. For this purpose, always select the tyre type and tyre size under Main menu > Tyre pressure > Adjustments in the instrument cluster. The control unit then learns the wheel positions again once the vehicle starts driving.
1. Install wheel electronics loosely at the valve (do not tighten) and position in valve bore together with valve and bead seat sealing ring.
2. Fit washer, chamfered on both sides, and screw on union nut until it is seated correctly. Visibly twist bore at the valve foot. Block with a suitable assembly pin if necessary. The tightening torque is 4 Nm (+/- 0.5 Nm)/3 ftlb. (+/- 0.5 ftlb.)
3. Push wheel electronics -A- slightly into the rim well (this adjusts the angle of inclination of valve to wheel electronics).
4. Carefully tighten self-locking (Torx) fastening screw T 20 to 4 Nm (+/- 0.5 Nm)/3 ftlb. (+/- 0.5 ftlb.). The wheel electronics should now be lying evenly against the rim.