I was thinking about the TPMS system in our 8's. I know they're part of the valve stem between the wheel and tire but how does it actually transmit information to the car computer when your tire is too low? There obviously can't be any wires since the wheel needs to spin freely. Do they have a wireless system to communicate with the ECU, are there batteries that ever need to be changed?

 

yep, because if you want to reset the sensor, if you have winter wheels for example, you can leave the wheels in the garage and they will communicate with the car.

 

sensors dont start to work till tire starts to spin.

beers

 

you sure? I have had my tire sensors go off once I moved the tires back into the garage....

 

Wow that's pretty cool, I didn't see anything about that in the manual. So if you have a set of wheels that don't have TPMS like track wheels then it will blink with that set on but if you put the OEM set of wheels/tirse back on then it will sense them again and turn off?

 

yep,

supposed to start working with centrifugal force.....

but you never know..

beers

 

yep, or if you have the wheels with the tires on in a close proximity to the car

 

all i can say is someone put 4 sensors in a pressurised tube to have the same effect...

did not work..

beers

 

i got to agree with swoope on this one, it starts working with cetrifugal force.

 

The shop manual says they start to work at 16mph.

 

I know, im reviving an old thread here, but mine does the same thing, but goes away soon after...

 

Thanks abbid!

 

so why does it go off when you start hte car and the car is still??

also, nobody ever answered how it communicates to the factory computer.

-hS

 

they work via rf and communicate with a central receiver, which in turn talks to the computer. I would have to agree that they are on when the car is started, as there would otherwise be no way for the car to produce that tpms light sometimes but not others. I would probably guess they turn off after a period of inactivity (motion stops), but receive a turn-on signal from the receiver when you switch on the car's computer.

 

They must work as soon as the car is started because a month ago, that's what happened to me. I hadn't driven the car in 2 days, turned it on and immediately got the low pressure light. (one tire was almost completely flat)