Tyre Pressure Monitoring Sensors (TPMS)
Tyre Pressure Monitoring Sensors (TPMS) are fitted to a wide range of vehicles and constantly measure the individual tyres pressure. There are many different types and the ones here are from an Audi Q7 4×4. They are fitted instead of a standard valve so care has to be taken when replacing tyres !.
The pressure sensor itself has an internal battery designed to last about 5 years and new sensors have to be “woken up” with a special tool to switch on the battery. They communicate with the vehicles central Electrical Control Unit (ECU) or Body Computer via radio transmission. This then displays pressure / warning information to the driver.
This particular type of valve is made from aluminum and do suffer very badly from corrosion as in this case all four aluminium valve caps were completely siezed to the valve housing and impossible to remove without damage. The recent harsh winter and subsequent use of road salt hasn’t helped. More alarming is an instance where the valve housing has fractured at its base whilst attempting to inflate the tyre thus projecting the housing and valve like a bullet causing total deflation.
These sensors are usually only available from the vehicle manufacturers as complete assemblies at a cost of upto £120+ EACH! and so it can be very expensive to change your tyres. Any replacement has to be “coded” into the vehicles management system to be recognised. Luckily we were able to find and source replacement valve assemblies with PLASTIC valve caps on this 3 year old vehicle.