TPWS - guaranteed to fail

i think there are tools available to diy, but my days of separating tyres and rims are long over

 

You can buy a new sensor and replace it, you can open the old sensor and replace the battery, or you can pay for the service of replacing the sensor by other specialists.
Everything depends on your desire and time.

 

Doing nothing is an option, at least till you’re in need of new tires. Unless you’re obligated to have functional sensors, car needs it to pass some inspection. Be extra vigilant regarding tire pressures. That’s basically how it was, 15~20 years ago.

just editorial: the acronym is TPMS, Tire Pressure Monitoring System.

 

Techstream allows you to both program and view sensor data. A little logic and it won't be difficult to determine which sensor has a low battery.

 

Autel sells tools which directly communicate via rf at each wheel. In addition they can read and write a sensor's serial number into the vehicles's tpms computer. They are several hundred dollars. Many small tire shops around here have them along with all the big chains.

However all you need is an obd2 scanner that can read the pressures. You then reduce pressures one tire at a time to determine each sensor's location.

Techstream and better scanners have a battery "over or less" field in addition to pressure and temperature. Apparently the "less" voltage bit is transmitted.

In this capture, taken before changing id3 and id4, I first determined location by reducing pressure while monitoring. In this case id4 tpms battery sensor showed "less" voltage prior to changing it.



The Autel tool below ($190 US) allows rf checks and obd2 read writes



The Autel tool works on all standard sensors. Standard sensors have a unique serial number assigned at the factory which is then needed by the TPMS car computer.

Aftermarket 315 mhz Toyota sensors for $40 a set work fine. An independent tire shop can install four sensors for $60. So there is really no excuse for allowing your family to drive on tires with 18 psi with resulting blowout or ruined tire potential.

Finally the above Autel tool allows use of a special Autel MX sensor that can be configured to match your existing sensor ids. This capability would allow winter wheels to be the same ids as your summer set, resulting in no loss of tpms when switching to and from winter wheels.

 

I thought the TPMS sensors had a piezoelectric element in them to give the sensor power when subject to road vibration. AKA no battery to die.

 

No they have batteries. There is a movement sensor to wake them up to maximize battery life from eight to ten years. They will wake up and transmit even when parked on a loss of air pressure or when polled by a system.

Honda and a few others have no tpms sensors but calculate a loss of pressure based on tire rotation differences between tires. They use the abs speed sensors. It is simple but has no psi reporting capability.

 

Toyota also uses this method to calculate the difference in tire pressure drop.

What is surprising is that when they supply the same car model to Europe or the American continent, they equip it with TPMS sensors, but for their market, they do not install TPMS sensors.