If you’re joining in from our article: “My TPMS Light Is On, I’m FREAKING OUT!” – you’re in the right place! Time for the low-down on TPMS transmitters!
A LITTLE HISTORY:
TPMS transmitters were made mandatory by the TREAD act and applied to all vehicles in the U.S. from model year 2008 and later. The point is to keep drivers alert of severe under-inflation and avoid a blow-out, which could cause injury or death in some cases.
Indirect transmitters use a vehicle’s ABS (Anti-lock Braking System) or ESC (Electronic Stability Control), or TCS (Traction Control System), to detect if a tire is low on pressure. Without getting too technical, essentially the indirect system makes calculations based on the rolling radius of the tire and even its rolling resistance – to then calculate how many revolutions the tires should be making given the current vehicle speed. If the tire is running low on air pressure, that would most likely result in a flatter (smaller rolling radius) tire – and therefore the wheel speed will not match with the ideal vehicle speed condition – and hence detect an out of spec pressure situation. This kind of system does have limitations based on road surfaces, driving speed, and driving style – and is steadily being phased out.
Direct transmitters are the most popular and consist of an actual wireless coin-cell battery powered transmitter mounted on the tire inflation valve stem (on the inside wall of the wheel. It has a port on it that directly measures the air pressure inside the tire/wheel volume and reports it at regular intervals back to TPMS control module (wirelessly) which talks to the car. When the sensor detects a pressure out of spec for a sustained period of time, it sets off the light in your dashboard – indicating a problem.
Drawbacks: the battery inside the transmitter will die, definitely. Usually they last about 5-10 years depending on manufacturer. Typically the batteries die within close timing between each other – so to avoid repeat hassles we recommend replacing all the sensors if you see one or more sensors with a failed battery. Cost of replacement sensors varies from $30-$80 depending on year, make, model of vehicle.
Different transmitter frequencies: Different TPMS systems operate on different TPMS frequencies – therefore care must be taken when replacing the sensors to ensure they will be compatible with your vehicle’s system.
Snap In VS Clamp-On Valve Stems: Different vehicle have different requirements on whether they use a rubber snap in valve stem, or a clamp-on metal valve stem. It’s important the correct system is chosen in order to ensure a tight air seal between the wheel and tire valve to avoid air pressure leaks as well as sensor errors.
Important tip: anytime a tire is dismounted from a wheel, the tire valve stem and associated seals (Usually called a “TPMS Service Kit”) MUST be replaced. These are one-time use, soft deformable items – which ensure an air tight seal with the wheel – skimping on this means air leaks and a bad day for you!
TPMS Relearn Procedures: Different vehicle manufacturer require different relearn procedures to make sure your sensors work correctly with your vehicle. To do this correctly, specialized diagnostics tools are necessary and the proper procedures must be followed to ensure your safety on the road.
It’s for this reason we recommend a professional to handle this task to ensure your peace of mind.
So that’s a quick run-down on TPMS transmitters/sensors. For more info on specific recommendations for your application, hop over to our TPMS service link.
Avoid interruptions to your day. Wth getTREAD, you can rest assured you’ll get the right transmitter/sensor for your needs – and of course – we COME to YOU!