Tire Pressure Monitoring System TPMS for my JEEP   

Not  needed in 100 years, but now here it is and what a PITA it is.  (the nanny state) FED laws.
It's for folks too "drunk" to look  at tires, before driving, or failing to notice while driving the car steers funny  and then not stopping and looking.
What you get now, is 1 more (of the 30) Idiot light's blinking and you ignoring that too.
All cars 2008  and newer. (USA)
end rant...
The light comes one 25% low, so 27 PSI on my JK, 36 is normal.
News flash,  my 2010 WK Laredo Jeep , the tool has no 2010 listed, but by pure luck the VW 2009 ROUTAN works perfect. My R/Fr sensor was dead, (scanned) the local garage swapped them for $10 (flat tire fee), (with my Dorman 974-061)
I got cheap work done beause I said, "It's my problem if my new sensor does not work" bingo, no overcharging.
He set  the pressure to 36 PSI , 3 over spec. then we parked for 20 minutes; I scanned it , and it's no longer dead ! (shows pressure and temp and SLEEP, then drove for 1-10 miles (autolearn works), and SLEEP ended and dash lamp went out. Done deal.

But,? Now  more bad news on JK jeep. 
If your sensor is dead, like mine, the silly VFD display window in the cluster just shows, "TIRES"  (I don't have smarter EVIC display in this cluster)
If lucky , my nice scan tool will tell  me which of 5 tires are failing,  yes, all 5 tires (yes, the spare too) (It did)
But if you are away from home, maybe the scan tool is there too, and my TPMS scanner too. (just kick the tires and drive,gee)

The tire store will charge you $100 more to fix the bad sensor with labor more. (keep a spare, in the glove box,  they are cheap from DORMAN)
The Tire store may (it's their call) refuse to mount said tire (new ,used or patched), if the sensors are missing or bad.  FED T.R.E.A.D LAW is not clear but  , they made these examples. (DOA , rules)
The tire shop must not take a good sensor and  render  it dead, or shut down the system. But he can put in any stim he wants (live or dead) in a wheel with a dead sensor already.. Dead for Dead is fair game.
The Dealer will refuse  to disable it, but may agree to set pressure down to 25 PSI. (or above) only. never 0.  (if using custom DOT rated larger tires)
The dealers tools are blocked below that pressure ! (he is blocked by law and so is that factory OEM tool)
If the shop broke your sensor (the machine he uses loves to do that) and he has no spare, I guess you don't get your keys back, until he can get one.  (NICE stranded from home bad news) Your  car is in JAIL.  (who gave them that authority? and power?)

New sensors are activated by just driving. (no need for a tool to do that , unless running a shop) (or use a  donut magnet tool to wake it up first.)

But having a real scanner is needed, in many cases, (see the data sent and know what is going on)
In many cases you need to see what sensor is bad (or many) and why, overheated? , dead, or wrong pressure readings.
The tire scanner is cheap now, I have the CUB pro-101  (got mine on sale for $25, new)
The display is weak,  I must scan , hear the beep , run inside, and see the message.  My WK jeep beeps in about  2 seconds flat. (with pressure, temp and active) If battery is dead so will all scans fail. (no beep)

The ATEQ VT30 tools is too expensive at $200

I keep spare DORMAN 974-001 in my cars hidden tool box, just in CASE !

Off Road running  and with  big tires.  HACK #1
Say you are running 33" tires.  and get sick and tired of the stupid bells and lamp flashing, yes, there is hope.  (mine works 2008 to 2015 now, no problems)
The cure is the "Super Chips" Flashcal  3570 tool.  It can only do one, car. (it memorizes YOUR V.I.N.  and refuses to work on a car #2, so you must uninstall it on car 1 to go to car 2 (say you sell 1 jeep and buy a new one) sorry can't do a fleet of cars with one tool, (by DESIGN)
You buy the tool., and must register it, and download the TPMS package software (after 1 phone call and getting permission !, first and signing and sending a SIGNED release form) then you can disable it.  (got all that?)

Hack 2 is better. Real Cave man simple (PCV pipe & 2 end caps and one mounted schrader valve (fuel injection type or air) Put in 5 sensors and glued , put in 32 psi air pressure, put this pipe under the car seat strapped to springs there and forget TPMS. (can be made for under $35)
Best of best lay out.  I've not tested this hack.... But I'm sure it will work activated. (many report it does)

Now begs the question, what if there are too many working sensors, say 6 or 10?  (what if 2 Jeeps same year or span 07-2011 were parked side by side, see how this works?)
The TPMS system usually accommodates up to 10 sensors at a time. (2 sets of tires (8) and 2 spares) . (sure all must be activated (learned) to swap freely.

You could put in one sensor (after activating it) and then hide a dead sensor on car, or add them to the PIPE as each battery dies in the tires.
The puter is stupid, it just scans the list of known 10 sensors and stops when 5 scan good.  (think about driving to tire store with 4 active spare tires/wheels in cargo area. (it sees now 9 tires and is happy?)
The works because active sensors, transmit , while parked. (0 MPH)
A real head scratcher here,  but I got it.
Now what happens when 1 sensor is dead, on your car and you park next to a good Jeep, your Jeep sees alien ID and ignores them, but what if both are going 20 MPH side by side, oops?  My guess is 1 uWatt (1 micro watt) RF signal can't go that far.
My guess is you have 10 sensors, and 5 are active and all 5 read ID okay, and 5 have fibbling PSI ,say all 5 have 5PSI no matter what? oops, I bet you need to kill the those dead someway.  (not tried, yet ,I'm too cheap)

JEEP FSM 2008 JK, quotes.
Using an RF signal, each sensor transmits tire pressure data approximately once every minute.
'Each sensor's (transmitter) broadcast is uniquely coded so that the WCM can monitor the state of each of the sensors on the 4 rotating road wheels. The WCM automatically learns and stores the sensor's ID while
driving after a sensor has been replaced. There is no formal retraining procedure necessary.
Once the vehicle has remained stationary for more than 20 minutes, drive vehicle for a minimum of 10 minutes while maintaining a continuous speed above 15 mph (24 km/h).
 During this time, the system will learn the new sensor ID's."
My guess is the WCM stops looking for new sensors after 5  are found. (so if that is true the above pipe with 1 sensor, would just be learned after they are activated.
Keep in mind you need to spin the new sensors, 1 time.
The problem arise with one sensor in the a tire, is not dead buy fibbing its plants off,  high temp, or low pressure lies &data scrambled. (so it must be removed, or killed in some one, I have a nice HV cattle probe that can kill one is 1 second !)

The sensor maker adds more facts:
Battery life 3 to 10 years
To actvate a new sensor outside the confines of the tire is tricky, you need to spin it at the end of a string fast (20mph fast) , key on,near car. (try not to hit the car, ouch)
Or use a magnet ring, sold in stores.
Turning on the key , forces the sensors to transmit their data.  (they can RADIO signal collide, but keep trying until sucessful  , so you don't drive off with a low tire.)
The sensors are color coded, do not buy the wrong sensor.
After activation, the sensors transmit every minute.
That is why I can use my scan tool, key off to see all data from each sensor 1 by 1,  (pressure, temp. and ID)

rev 1   ++++ 3-12-2011