TPMS reset and amazing accuracy

[justanotherdrunk]

the tire pressures were down about 3-4 psi each

set 'em all to the pressures shown on the door sill

Fronts 33
Rears 41

successfully drove around while the TPMS reset itself

it's amazing how close my 2 year old (el cheapo) digital tire pressure gauge compares to the cars readout

no more that 0.3 psi deviation on all 4 wheels!

Do the wheels actually have pressure gauges in the valve stems or does it measure wheel rotation and then calculate?

or some other means?

thanks

 

[alohart]

Do the wheels actually have pressure gauges in the valve stems or does it measure wheel rotation and then calculate?

or some other means?

Apparently pressure sensors are standard in the U.S. market but wheel rotation sensors are used in some other markets (e.g., Canada).

 

[jadnashuanh]

Many TPMS have an actual pressure sensor, but not all cars will display it or translate it to a specific readout. When you run the reset program, the car stores the current digital reading, then looks for a drop to trigger a warning. Those without the sensors, use the antilock brake rotation sensor, and look for a variation in rotation rate from the other tires...if all of them lose air equally, it may not be able to tell you have a problem since the difference won't exist.

FWIW, the service manager said that on the i3, the receiver is actually the key fob! This saves some weight verses the way they actually do it in (most?) of their other cars...then, the fob tells the car the results.

 

[nitramluap]

FWIW, the service manager said that on the i3, the receiver is actually the key fob! This saves some weight verses the way they actually do it in (most?) of their other cars...then, the fob tells the car the results.

Surely that can't be right?! How does this 'save weight' if you have to have the key on you when driving! :roll: Smells like nonsense to me.

 

[jadnashuanh]

FWIW, the service manager said that on the i3, the receiver is actually the key fob! This saves some weight verses the way they actually do it in (most?) of their other cars...then, the fob tells the car the results.

Surely that can't be right?! How does this 'save weight' if you have to have the key on you when driving! :roll: Smells like nonsense to me.

It's one less module you have to have in the car. There already is a module that communicates with the fob...most other cars have a dedicated module for this.

 

[nitramluap]

It's one less module you have to have in the car. There already is a module that communicates with the fob...most other cars have a dedicated module for this.

Well, it might be easy to test. Start the vehicle, hand the key to someone outside the car through the window and drive off for a while, then check the tyre pressures on iDrive (or get someone to let air out of a tyre) and see what happens.