Article on how TPMS sensors operate

[John E Davies]

“HOW OFTEN IS A SENSOR TRANSMITTING INFORMATION?

This varies among manufacturers, but generally, sensors have different settings while parked and while in motion. The better question is what causes the sensor to transmit? When a sudden change in pressure is detected, the sensor should transmit whether the sensor is stationary or moving. When the tire starts to roll, tiny accelerometers cause the sensor to wake up and start broadcasting at regular intervals. In rolling mode, sensors transmit, on average, once every 30-120 seconds. While parked or in stationary mode, depending on the manufacturer, sensors may transmit only when a significant pressure change is detected. 

If a TPMS sensor transmitted all the time, a sensor would not last very long.  Most TPMS sensors will transmit when movement is detected through a simple accelerometer inside. If the wheel stops moving, the sensor will stop broadcasting after a programmed amount of time. But once it is triggered, the sensor transmits on a predetermined interval set by the manufacturer. A sensor will immediately send a signal if it detects a sudden loss in pressure.”

https://www.underhoodservice.com/tpms-radio-frequency-theory-and-operation/

Mine has screw on sensors, and when getting ready to leave in the morning I “wake up” each one with a couple of raps from my finger so they transmit today’s value, not the one from when I arrived, in case one of the tires picked up a nail and was quietly deflating overnight. I would much prefer to see that warning or low pressure reading in the campground than a couple of miles down a busy highway… and this is a great reason to NOT choose a type that installs inside the tire. You can’t wake those up except by driving away.

John Davies

Spokane WA

[GraniteStaters]

We have a Tuson TPMS system with internal TPMS and it is installed in our LEII tires and spare and is very good.  They provide a transmitter for the trailer if it is longer than 18 feet as I recollect.  I installed it too.   I was curious on how it reads the spare and was pleasantly surprised to get the info when the trailer is moving.  I purchased the activation tool from them to ease the configuration for the spare’s TPMS which was purchased separately.  The activator sends a signal to the TPMS that simulates a pressure drop.  Alternatively without this tool, I would have had to bleed air from the tire.  I opted for the tool.  It ended up being important for me to use on the other TPMSes installed so I could get all the tires displayed in the right order.