TPMS and the Five-Wheel Problem

Hi all,
This is my first post on this forum.
I have searched high and low for an answer to my question, but haven't found anything, so here goes:
I want to get a spare tire for my 2015 Tacoma that matches the four new offroad tires I have put on it. These have TPMS sensors in them.
I would like to rotate the spare with the other tires, so it would make sense if it also had a TPMS sensor.
The problem is, the local dealer tells me that the 2015 Tacoma system will only handle four sensors at a time. So a fifth sensor will not give me any meaningful info about the state of my tires (i.e., if one road tire runs low, the light will stay off because with the spare tire on, there will still be four healthy signals coming into the system).
Anyone have any suggestions for a workaround?
I am also wondering if there are external TPMS sensors (that screw on to the valve stem, like a valve cap) that would work with a Tacoma. This would seem to be the ideal solution, but I have not seen anything like this (https://www.amazon.com/ENKLOV-Wirel..._4?s=automotive&ie=UTF8&qid=1511053489&sr=1-4) that appears compatible with the Tacoma's TPMS receiver -- they all use standalone receivers that plug in to the 12V outlet.
Thoughts?

 

So in theory you could have a deflated spare tire and not know it. This makes no sense.

 

So...why not just run 1 tire without a TPMS? If you have 4, you’ll always know you have 4 full tires. If the 5th goes flat, then you have a full size spare.

Or do what millions have done before you and don’t run a TPMS. I disabled mine when I went to aftermarket wheels.

 

Hmm. You do have a point. Maybe I'm overthinking this whole thing...

 

Go without TPMS like it was 1990. Or, keep your spare under inflated (25 psi) and carry a portable air compressor. The

$91 Viair 88P Portable Compressor Kit (12V, 120 Psi, Forup to 33" Tires)

Viair 88P is outstanding for the price. Air up the spare when you need it.

 

one time my "low tire pressure" light came on and I didnt know why, I took it down to the tire shop, they squirted a bit of air into my spare and the light went out... now, that dont square up with what the dealer told you, does it?

 

I have 5 matching wheels and tires on my 15 as well. They all have TPMS Sensors in them, I will be rotating the spare into my rotations, and the place I get them rotated reprograms all 4 before I leave at no charge. So it is doable. But that monitor you show will only show the 4 tires that are rolling

 

FWIW my dealer told me that 2016's have a 4 sensor system without TPMS in the spare.

 

What year is your truck? I have read that older ones (pre 2015 at least) supported five sensors.

 

How does the receiver tell between the signals on the 4 installed tires and the one coming from a spare in the back?

 

Because he goes around to the 4 on the ground tires gets the numbers off them and runs it into the OBDII

 

Here's how it works. The truck senses wether or not it is in close enough proximity to 4 functioning sensors that transmit a desirable reading. I have 2 sets of wheels with tires on them and a spare. The spare does not have a sensor. One of the sets of wheels also does not have sensors. The other does. When I switch from winter to summer wheels (or visa versa) ... If the wheels without sensors are on the truck and I am not near the other set, my TPMS light is on. If I drive around with the set that has sensors in the bed of my truck, the light does not come on.

You can even do a 5 tire rotation if you like. As long as 4 have working sensors, you're good. If your spare has a good sensor, you could get a flat and the truck may not notice, as there are 4 good sensors in proximity. I could also be wrong about that part. One sensor sending a "red flag" signal might set off the light. I'm not sure.

 

In techstream there is a field that shows how many tpms sensors came from the vehicle from the factory. Location of the sensors have no bearing on this. Vehicles with 5 sensors do not know if a tire is in the bed of the truck or on your vehicle.

I see no options in changing the number of sensors either.

I probably have 20 vehicles a day in the service drive when it gets cold for air.

 

Why did they go to a four sensor system? My 06 supports 5. That’s weird

 

It's hit or miss it seems to be honest never took the time to verify which years have them. So many vehicles went to donuts and no Toyota without a full size spare has a sensor.

 

Mine is an 07 Sport.

 

The '15 owners manual says that the spare doesn't have a sensor but it also calls it a temporary tire. The Tacomas obviously have full size spares the same as the rest of the vehicle. Confusing.
I'm tempted to let air out of the spare and see if the light comes on.

 

So did you disable the whole TPMS? I am putting aftermarkets on soon, and my old truck doesn't have tams, so I don't care about it.

 

There is the magic secret.

And 'no charge' is magic secret #2.

 

Your disablement method?

Lots of posts around on the topic, but success seems to vary wildly by year model (or maybe user)

I'd gladly do w/o mine, particularly when they finally fail.