Tire Pressure Sensor: Service and Repair
WM 443219 Removing and installing wheel electronics
Technical values
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 stationary. One wheel electronics unit -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 corrected.
There are different types of wheel electronics units -A-. Some of these are not compatible and send signals in various frequencies.
Information
To differentiate the wheel electronics, a table is stored in GFF (Guided Fault Finding) in the Porsche System Tester. Please note the following path:
- Select Fault finding]]Vehicle type]]Model year]]Model]]TPM]]Guided Fault Finding. Press the Jump key (footprints). Select Function/component selection]]Chassis]]TPM]]Inspections/tests]]Wheels/tyres]]Wheel electronics]]Nominal values button[[.
- See also => 443200 Tyre Pressure Monitoring (TPM) system not active after changing wheels.
The following points can also be used as distinguishing characteristics:
- The labelling - 433 MHz or 315 MHz, depending on country classification
- The part number
- TPM system and wheel electronics generation
- The colour of the housing up to and including model year 2006/1st generation (433 MHz - dark grey and 315 MHz - light grey)
- The colour of the housing up to and including model year 2006/1st generation (433 MHz - orange and 315 MHz - dark brown)
- 2 x 4 stars for enhanced transmission power up to and including model year 2006
- The colour of the housing as of model year 2008/2nd generation (433 MHz - dark grey and 315 MHz - light grey)
- No stars on the housing as of model year 2008
2nd generation wheel electronics units with a slightly modified housing are used as of model year 2008.
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 recognise wheel electronics units up to model year 2006/1st generation
- The old system does not recognise wheel electronics units as of model year 2008/2nd generation
Valve and 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 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.
Every tyre set or wheel change must be communicated to the control unit. In particular, this is necessary when wheel positions have been interchanged. To do this, always select the tyre type and tyre size under main menu > Tyre pressure > Settings in the instrument cluster. The control unit then learns the wheel positions again while the vehicle is driving.
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 recognise wheel electronics units up to model year 2006.
- The old system does not recognise wheel electronics units from model year 2008 onwards.
1. Clean the valve bore very carefully (visual inspection).
Information
When replacing the wheel electronics -
- Always use a completely new valve.
- Always use a new fastening screw.
2. Install the wheel electronics unit loosely at the valve (do not tighten) and position it in the valve bore together with the new valve and bead seat sealing ring.
Information
Counter the new valve with an assembly pin (supplied with the new valve).
- The valve-stem seal may become twisted and can cause damage.
3. Fit the washer, chamfered on both sides, from outside and screw on the union nut until it is seated correctly. Visibly screw in the bore at the valve foot and block it using the supplied assembly pin.
Countering TPM valve while tightening (shown as an example)
4. 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).
Information
When tightening the wheel electronics unit/valve, tighten to the specified tightening torque evenly and in one movement. The tightening process must not be interrupted.
- Remove the assembly pin after tightening the components.
5. Tighten self-locking (Torx) fastening screw T 20 to the specified tightening torque => Tightening torque: 4 Nm (3 ftlb.)+/-0.5 Nm (+/-0.5 ftlb.). The wheel electronics unit should now be lying evenly against the rim.
6. 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.
Information
The wheel electronics must not come into contact with the tyre mounting paste or solvent.
When mounting tyres, ensure absolute cleanliness around the wheel electronics unit.