What exactly is the deal with our TPMS units? I just bought a used rear rim to swap out my trashed origional. The guy slapped my tire on it before I could ask him to move my old rims tpms to the new one. It's OK, he says, the computer will read it ok since it isnt a tire specific warning, you know, LR/LF etc. So I start my car and the low pressure light is lit. He says cause the old rim is in the trunk and the computer is reading it as flat....Sounds ok to me but what do I know?

So today I called the dealer, the tire shop is closed, and asked whats up. He says the cars computer will read only the sensors that have the same barcode serial number and that the tire shop has to indeed put the old sensor inj the new rim.

Arn't these sensors interchangable? is there a reprogramming reset thing I can do? thanks for any help

 

The guy at the tire place is full of it. If he would have re-installed the TPMS on the new rim you would be fine. If not you will have to reset your TPMS to recognize to new one.

 

good to go/know. They switched it back to the origional and the light did stay on however after about 1/4 mile down the road it went off

 

Yes, you have to drive on it to be recognized.

 

What I want to know is this: Where is the source of power for the Sensors in the rims? What, are there batteries in the sensors or is there an accelerometer thingy that, when the wheel turns, produces a tiny amount of electricity to power it?

And how does it communicate to the car's computer? Does it send a radio signal? If not, HOW does it do it?

I'v googled and gone to "How stuff Works" and posted on "All about circuits" and no one knows.

EDIT: Wikipedia http://en.wikipedia.org/wiki/Tire-pr...itoring_system had some answers.
Now I all have to do is find out if ours are "direct" or "indirect" systems. Sounds like we have battery operated sensors which use RF (radio) signals to tell the car that we have a low tire.

I hate to go by what Wiki says...