How does the dashboard tire pressure read out work?

I’m going to make a wild guess on how the tire pressure readings get to the dashboard; and go easy on me if I’m way off base, because I?m a long ways from my first vehicle which was a 54 Merc.

Actually I’m not interested in the whole pressure reading trip; I’m just interested in how the pressure readings get from the tire to what ever sends it to the dash. Since there is no connection to the tire other than lug nuts, “that I can see ? and I have rotated the tires,” I have to assume that there is some type of “sending device” inside the tire that senses pressure and then wi-fi’s it to a receiver and then on to the dash. I did notice a small plastic tube to each tire location which were not brake lines, and I also assume that this plastic line is part of the pressure reading system. OK folks I?m sitting down?? how far off the mark am I?

Thanks in advance for any info…Bob

There are currently two tire pressure systems currently in use.

The indirect system just uses the ABS to sense differences in wheel speeds. Such differences indicate low tire pressure in one wheel. This method is cheap. A criticism of this system is that it will not detect low pressure when both wheels on the axle are down.

The direct system installs a sensor/transmitter in each wheel. Each sensor transmits at rf frequencies to the computer which figures out what to display on the instrument panel. This method is more accurate but more costly.

Good question. Wondered that myself. We just bought an 07 Jeep and it took me the longest time to figure out what that darn light was for!

I was driving a 2004 Ford minivan from the fleet of the institution where I am employed. The low tire pressure light tripped when I was driving on a section of interstate highway that had been milled for repaving. Apparently the vibration caused the tire pressure light to go on. This was at 1:30 a.m. in the morning and the interstate had one lane open with no place to pull off, so I had to keep going. When I finally was able to get out of the construction zone and into a rest stop, the tires all seemed fine. Fortunately, the owner’s manual was in the glove compartment and I found out how to turn this light off. It stayed off for the rest of the trip.