TPMS question...

[Martinjmpr]

So my 4runner is the first vehicle I've ever owned with TPMS.

First time I noticed it was in July of last year when we did a little bit of mild 'wheeling up on the Alpine Loop (Cinnamon and Engineer Passes) in Southwestern CO. I aired down my tires to about 20psi and of course, got the low tire pressure warning light on the dash.

I also had a few incidents this Winter where super-low temps would cause my tire pressure to drop enough to set off the sensor (happened to my wife's car, too.) I pumped them back up and they were fine.

So I finally got around to putting my new-to-me tires and wheels on. The wheels are 17" steelies from an FCJ. They have rubber stems and (at least according to the guy who sold them to me) no TPMS transmitters at all!

Needless to say, I expected to get the TPMS warning since there was no information going to my sensor from the tires, but was quite surprised to find that no warning lights were on at all.

This leads me to two possible conclusions: Either

(1) the FJC tires do, in fact, have a TPMS sensor and it is sending the signal to my 4runner's computer, or

(2) the TPMS system must have some way of detecting that there is no signal and thus turning off.

I've pretty much rejected (1) because of the rubber valve stems (my understanding is that the TPMS sensors are located in the valve stems and that rubber valve stems do not have sensors in them) and also because there is pretty much zero chance that any TPMS sensors in a randomly purchased set of tires would be readable to my vehicle's computer.

So am I right with (2) above? Is there something in the TPMS that "knows" there is no signal being sent and turns off? Or is in the case that with no TPMS signal, the system reports "all clear?"

What's funny is that I had assumed that with the new wheels, I'd have to de-activate the TPMS, but as I was driving around yesterday with the new wheels on, and no TPMS sensor, I realized I would not have to do that!

 

[R.A.]

So where are the original wheels and tires with TPMS?

Edit: I suspect in your garage. Your vehicle's computer is reading the old TPMS and accounting for them. There are numerous threads about this.

 

[kevinpt]

I have a replacement in mine that has a rubber stem

 

[ebg18t]

How far of a drive did you take? I would expect then to come on as you roll down the street. The TMPS transmit range is pretty good. So if you are just in the driveway they might be getting signal from your garage or where ever you are storing them.

 

[Martinjmpr]

So where are the original wheels and tires with TPMS?

Edit: I suspect in your garage. Your vehicle's computer is reading the old TPMS and accounting for them. There are numerous threads about this.

How far of a drive did you take? I would expect then to come on as you roll dish the street.

Drove to Home Depot, probably 2 miles away. I don't think the TPMS sensors in my tires would "reach out" that far!

I have a replacement in mine that has a rubber stem

But I thought the codes for the sensors had to be "programmed in" so my computer could recognize it?

Not sure. Right now the 4runner is sitting in my driveway with the dashboard torn apart waiting for my new stereo to come in (should be in today!) so I'll have to see how it does in the future.

Funny thing is, as recently as last week, the TPMS light came on when we got a cold snap, so I know the sensor works.

 

[R.A.]

Try an experiment with one or more of the original wheels with TPMS and lower the PSI to 20. See if the light comes on.

 

[ebg18t]

Not sure Martin. Maybe you lucked out and the steel wheels have TPMS in them. I guess that is good news since you won't have to worry about the bypass mod.

 

[chaz]

if all you take are short drives & the old wheels are in the garage, the light may never come on. from what i remember you have to drive over 1-2 hrs or more then 50 miles away for it to light. The reason some are able to travel many miles away from the stored wheels is that the system "clock" resets every time the vehicle is shut off. mine are in the garage, the longest drive ive taken was 2 hrs & it didnt light up. and yes i know it works cause it lights when the spare is low or in winter when the stockers may get low.