We specialise in Tyre Pressure Monitoring System (TPMS). We can do all Makes and Models.
What is TPMS?
TPMS stands for Tyre Pressure Monitoring System, a safety feature that continually monitors a vehicle’s tyres and alerts the driver to changes in tyre pressure. The changes in tyre pressure can be detected by either Direct or Indirect means but both methods will, as a minimum, illuminate a warning light on the vehicle dashboard display and sound an audible alert when 25% deflation has occurred. Early TPMS was first introduced as an option on high-end luxury vehicles as early as the 1980s, although it wasn’t until the year 2000 that it was first fitted as a standard feature. Each wheel of the vehicle has a sensor fixed to monitor the changes in pressure from the tyre. Tyre pressure sensors also measure temperature. Each sensor sends its signal to the receiver inside the vehicle using a wireless connection. In Europe the transmission frequency is 433Mhz. If low pressure or a leak is detected (generally 25% less than normal operating pressure), the driver is alerted by the in-car system and generally the deflated tyre is identified.
- Direct TPMS is very accurate measuring to 1 or 2 psi.
- A puncture after parking is immediately identified.
- Sensors send their signals approximately every 30 seconds, when parked they transmit every 20 to 30 minutes. At 25 kph the sensor switches back on to transmit every 30 seconds.
- Sensors have an approximate life of 5 years or 160,000 km.
What does TPMS stand for?
TPMS stands for Tyre Pressure Monitoring System
Direct and Indirect TPMS - What’s the difference?
Direct TPMS - Each wheel of the vehicle has a sensor fixed to monitor the changes in pressure from the tyre. Tyre pressure sensors also measure temperature. Each sensor sends its signal to the receiver inside the vehicle using a wireless connection. Indirect TPMS - Indirect tyre pressure monitoring systems do not use pressure sensors to monitor tyre pressure, they work from the ABS or speed sensors on the vehicle. Indirect systems monitor tyre pressure by assessing the rotational speeds of each tyre, and work on the premise that an under-inflated tyre has a slightly different diameter than a fully inflated tyre.
What is a sensor ID?
Every TPMS sensor has it’s own, globally unique, ID number. No two sensors share the same number, even if they are of the same model. This unique ID number allows the vehicle to recognise with sensors belong to it, and also recognise which sensor belongs to each location on the car.
When a tyre is replaced or a puncture repaired on a vehicle without TPMS, it is normal practice to replace the rubber valve. For vehicles fitted with direct TPMS, it’s no different. The valve part of a TPMS sensor is susceptible to deterioration, just like a regular snap-in TR414 valve. There are two basic types of TPMS sensor valves - snap-in and clamp-in. The process of servicing each type is slightly different.
Servicing a Snap-in sensor valve
Servicing a snap-in type sensor is relatively simple. If the sensor is still functioning, it is simply a case of unscrewing and
discarding the old valve stem, and screwing on the correct replacement. There are several different snap-in valves that all look similar, so it’s important to ensure that the correct one is selected.
It is imperative to screw the new stem on to the sensor using a torque-limited screwdriver, set to the correct torque level as stated by the manufacturer of the valve. Over-torquing can cause irreparable damage to the sensor.
Servicing a Clamp-in sensor valve
With a clamp-in TPMS sensor, there are more parts to replace. Typically, a complete ‘Service Kit’ will be used, that is specific
to the valve. The service kit will compatin all the parts required.
The Metal Sealing Washer (1) (if fitted) often becomes distorted, replacing this ensures a good seal when reassembling the sensor.
The rubber sealing grommet (2) which deteriorates just like the rubber valve.
The Outer Collar (3) is replaced because it becomes metal fatigued, and sometimes badly corroded. This metal fatigue can often make the outer securing collar crack and sometimes this will fall off completely.
The Core (4) is replaced to create a good airtight seal in the sensor internally. Only Nickel plated cores should be used in Metal Valves.
The Cap (5) is replaced with a new pressure cap. Again the rubber washer in the old cap deteriorates, replacing the cap helps keep the sensor airtight and free from debris, or fluids that might affect the operation of the core.