Tire Pressure Sensor: Service and Repair
Removing and installing wheel electronics
Removing 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 stationary. One wheel electronics unit -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 corrected.
There are two different types of wheel electronics units -A-. Electronics units with amplified transmitting power are used on the Cayenne. These transmit in the high frequency range:
^ 433 MHz or 315 MHz.
The following points can be used as distinguishing characteristics:
^ The labeling, 433 MHz or 315 MHz
^ The part number
^ 4 stars on left and right of the slot (wheel electronics with amplified transmitting power only)
^ And/or the color (dark grey 433 MHz; light grey 315 MHz).
Wheel electronics units with a slightly modified housing in a different color are used as of model year 2008. The porous surface on the back (used to measure the internal pressure of the tire) distinguishes these electronics units.
^ Up to model year 2006: rectangular surface
^ As of model year 2008: very small round surface
The wheel electronics units as of model year 2008 are not compatible with the wheel electronics units up to model year 2006. In other words:
^ The new system does not recognize wheel electronics units up to model year 2006
^ The old system does not recognize wheel electronics units as of model year 2008
Valve and wheel electronics
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
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 tire fitting paste or solvent!
Every tire 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 > Tire pressure > Adjustments, always select the tire type and tire size. During driving, the control unit then learns the wheel positions again.
The wheel electronics units as of model year 2008 are not compatible with the wheel electronics units up to model year 2006. In other words:
^ The new system does not recognize wheel electronics units up to model year 2006
^ The old system does not recognize wheel electronics units as of model year 2008
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.
Caution:
Increased risk if assembly pin left in valve
^ The tire-can be damaged during assembly.
-> Remove assembly pin after fitting valve.
-> Carry out the tightening procedure to the specified torque for the valve in the rim once only.
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 securely. 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 unit -A- slightly into rim well (this adjusts the angle of inclination of the valve with respect to the wheel electronics unit).
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.