Tire Pressure Sensor: Service and Repair
WM 443219 Removing and installing wheel electronicsRemoving wheel electronics
General information on wheel electronics
The tire pressure monitoring system is designed to constantly monitor the tire pressure during driving and when the vehicle is stopped. One set of electronics -A- 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 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 color (black = 433 MHz/grey = 315 MHz).
-A- - Wheel electronics
-B- - Valve complete (No. 2 to No. 7)
-1- - Self-locking (Torx) fastening screw
-2- - Valve cap (plastic)
-3- - Valve insert
-4- - Union nut
-5- - Washer chamfered on both sides
-6- - Bead seat sealing ring
-7- - Valve
Removing wheel electronics
Information: For vehicles with a tire 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:
^ The housing is visibly deformed
^ The filter surface (square, porous section on back of wheel electronics) is so badly soiled that it can no longer be cleaned by wiping
^ Tire sealant (tire 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 tire, the wheel electronics -A- can be seen at the valve in the outer rim well base.
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 [diameter] 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 tire can be damaged if the assembly pin is left in the valve.
Information: When coating the rim with tire mounting paste, make sure not to coat the area around the wheel electronics. Tire 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 tire 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 tire type and tire size under Main menu > Tire 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 T20 to 4 Nm (± 0.5 Nm)/3 ftlb. (± 0.5 ftlb.). The wheel electronics should now be lying evenly against the rim.