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Info On Tire Pressure Monitoring Systems (TPMS)

I had a class the other day for work, and it was all about the Tire Pressure Monitoring Systems coming out on newer vehicles. I found out a good amount of information. I wanted to share it with the 03-newer Explorer owners, because most newer Explorers-Mountaineers have the TPMS!

What's Covered In This Section:

1. Hard Facts (Sub-Categories: (a) Reasons Why)
2. Two Types Of TPMS (Sub-Categories: (a) Indirect, (b) Direct, (c) Old Fashion)
3. What/Who Uses What
4. How Do I Know I Have It
5. Changing Tires and Wheels
6. How Do They Relearn
7. Aftermarket Wheels and Tires

Hard Facts:

-- NHTSA - New proposed rule requires TPMS on all passenger vehicles, trucks, and buses with a GVWR of 10,000 pounds or less. (excluding duallys under 10,000 pounds)

-- 100% compliance is required by January 1, 2007 subject to phase in schedule: 20% by September 2005, 70% by September 2006, and 100% by Jan 2007.

Reasons Why:

-- The National Highway Traffric Safety Administration conduced an inspection of 6,240 vehicles within a 14-day period in August of 2001. Found that out of those vehicles tested, 27 percent of the passenger cars had one or more tires substantially under inflated. They also found that 33 percent of light trucks and suVs had one or more tires that were also under inflated.

-- About 8,000 blowouts every year result in serious injury or death.

Note: some TPMS check and warn about HIGH air pressure. The NHTSA mandated systems do not require high pressure warnings.

Two Types Of TPMS:

-- One type measures the pressure in the tire directly (Direct TPMS). The other checks tire pressure indirectly (Indirect TPMS) by testing the effects on the tire from the pressure change (i.e. - through the ABS system - wheel sensors).

Indirect TPMS:

By watching the wheel speed sensors, the ABS module "knows" how fast each wheel is turning. Two modes of operation while driving: Calibration and Detection. After tires are rotated or replaced, the "reset" button must be pressed to clear the prior saved calibration from its memory.

When the vehicle reaches a predetermined speed (or speeds) for the first time after resetting the system, it enters into its calibration mode.

- In this mode, it "learns" how fast the individual wheels are spinning. It also takes a sampling of those measurments and saves those values in memory. It cannot detect a low tire in calibration mode.

The indirect method does not satisfy the NHTSA's requirements and will not longer be on new model vehicles after 2006. Diagnostics of these types of systems should not be a problem for any shop that does ABS systems. Same type systems, senosors, electrical devices, etc.

Direct TPMS:


The only method that currently satisfies the NHTSA's requirements. It works by use of a radio trasmitter located inside the tire:


The radio transmitter is actually the valve stem's base. The valve stem is part of the transmitter and serves double duty as an anchor and as an antenna. If the vehicle is equipped with a spare, the spare will have a transmitter as well. The first direct TPM sensors (like found on some older Corvettes) were a rather large sensor (approx. 3 inches long, 2 inches high, and a inch wide).

The typical modern direct TPM sensor has a 10-year lithium battery that is not replaceable. The sensor weights just over one ounce. It's accurate up to 2 PSI of its reading, and have been tested over 200 MPH. they carry price tags in the low hundreds each (higher for BMWs, Lexus, etc.).

Transmitters/sensors are not constantly on. They only send a signal about every 30 to 60 seconds at speeds of 15 to 20 mph. then, when sitting still, they transmit a pressure reading about once each hour.

Every manufacturers system is different, and diagnosing and fixing these systems vary. should the module determine pressure to be too low, or fail to recieve a signal, the TPM light will illiuminate (on top of page) or will state so in message center. This INCLUDES the spare tire!

If a tire is low, and you inflate the tire, the light should go out (if that was the problem). However, if the tires are rotated, then most of these systems require retraining the sensors/modules. The TPM system "knows" the placement of each tire (LF, RF, RR, LF, and spare), the technician must retrain the module each time the wheel assemblies are rotated. Or if the tires are replaced and the rims are not put back in the origional positions.

Old Fashion/Aftermarket TPMS:


What/Who Uses What:

Indirect TPMS:

- Ford: 2001-03 Windstar
- GM : 97-02 Park Avenue, 99-03 Century and Regal, 02-03 LeSabre, 2003 Rendezvous and Aztek, 00-03 Impala and Mone Carlo, 99-02 Alero, 99-02 Grand Am, 01-03 Aurora, 97 Grand Prix, 2000-03 Bonneville
-Toyota: Sienna Van
-Nissan: Pathfinder

Direct TPMS

-Chrysler: 02-03 300M and Town&Country, 03 Viper, 04 Pacifica
-Ford: '03 Explorer and Mountaineer
-Lincoln: 03' Navigator

-GM: 00-03 Deville, 97-03 Corvette (as well as some older Corvettes)

How Do You Know I Have TPMS:

-If it is factory equipped with Extended Mobility tires (EMT, A.K.A. "runflats"), then it will have a pressure monitoring system. Runflats are required by federal law to have a TPMS -- and any store that will sell you Runfalts on a non-TPMS, will require you to buy new wheels/Sensors.

-You can tell by a simple turn of the key or a look at the valve stem. Turn the key on the ON position and look on the dash for a light. If the vehicle is equipped with navigation, go through the menu and search for the TPMS. If you look at the valve stem and it looks to be metal/aluminum, and locked in place by a nut, more than likely you have a TPMS.

Valve stem looks similar to this:


-Be sure to inflate tires to the pressures specified on the vehicles data plate, no more going by the rating on the tire.

Changing Tires and Wheels:

If you replace new tires, it is highly recommend to get a new grommet, seal, and o-ring set. Replacing these seals are about $10 in parts per wheel. Here's a diagram:


The TPM valve stem cap is made of aluminum and the valve core is nickel-plated for resistance of corrosion. The outer end of the valve stem functions as the sensor's RF antenna. Always place both the cap and the sensor/valve assembly on a clean, dry surface when they are removed from the wheel.


- If the metal stem cap is stuck, DO NOT use plies to remove it -- it will break!
- DO NOT use a self calmping air chuck on the TPMS sensors, valve stems will break off! These things are VERY fragile!
- Valve Cores of the TMPS are not the same as regular rubber stems, do not lose them.
- DO NOT replace cap with a rubber one, it will mess up the transmitters
- DO NOT use "fix-a-flat" with a TPMS; it will clog the sensor and render it broken.

How Do They Relearn?

Different manufacturers use different ways to relearn or retrain the TPMS! Some use magnets with a certain process and some use a "reset" button. Here are some pictures of the magnets that GM Uses:



Aftermarket Wheels and Tires:

This information is still up in the air. Some aftermarkte manufacturers are trying to make wheels that'll work with the sensors, but the problem is that the sensors are made to fit on the wheel a specific way (flush against the rim). If it does not sit flush, it may break off during normal operation. Most systems will allow you to change for bigger/smaller tires. The biggest problem right now is with low-profiles and these sensors.

Of coarse, I would like to hear some feedback, corrections, and opinions about all of this stuff. I hope this will help some people out. I can probably get the "relearn" steps for a Explorer/Mountaineer/Navigator if you all think I should.


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Pita Tpms!!!

rick chi-town said:
I just put 20in Roush rims on my 2005 Expy equipped with the TPMS.... So now, every time I get in the car, I have to reset the on-board display with the error message "TIRE PRESSURE MONITOR FAULT" kind of a PITA!

I replaced the stock 17" chrome wheels with 20" U2 wheels. The sensors would fit the new wheels, but there would only be 1-1/2" inch of clearance between the sensors and the floors of the new low profile (P275/45/R20) tires. Therefore, I did not transfer the sensors to the new tires.

Neither my dealer nor Ford's Customer Relationship Center could tell me how to deactivate the TPMS. They had to have realized that people would want to use aftermarket wheels that might not accommodate the TPMS sensors. I'm still trying to find the one person at Ford who knows how to TURN OFF the TPMS. :fire:

In addition to the TMPS aggravation, the no one at Ford seems to know how to turn off the auto-dimming feature of the windshield rearview mirror. It still works even after I unplug the wiring harness. My rear windows came tinted very dark. At night, the auto-dimming feature makes it impossible to see anything except the headlights of the cars behind me. Therefore, I have to turn it off everytime I get in the SUV at night.:fire:

Other than these two aggravations, I love my '05 Explorer. :cool:




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Looks really good. Sorry to hear your frustration. You should look at see if the TPMS has a fuse. If it does, pull it and see what happens. Now that you have the new wheels on, whats the TPMS doing? Blinking at you?


Thanks for the compliment. When I first start turn the ignition, there is a loud beep and a warning message "TIRE PRESSURE MONITOR FAULT" on the message screen and the yellow TPMS icon under the speedometer blinks. Hitting the "RESET" button clears the alarm. The alarm also sounds every 45-60 minutes of continuous driving.

I thought about the fuse, but other things are on the circuits. The TPMS actually has two fuses: fuse #16 is for the power mirror, manual climate control, and TPMS; fuse #25 is for the mode-temperature actuator for auxilliary climate control, trailer tow battery charge relay coil, and TPMS. I have no idea which TPMS function is on which circuit.

Oh, by the way, I forgot one other aggravation: no power antenna. Everytime I go to the car wash I have to unscrew the antenna and cover the hole with electrical tape so that water won't get down there and cause a rust problem.

Someother cool stuff:

AutoPump System:


A new advanced tire pressure monitor system from SmarTire has been tested on some prototype Jeeps. This system or one similar may appear on future models. In conjunction with an automatic tire AutoPump made by Cycloid, this combined system automatically and continously re-inflates tire pressure to a specified level, ensuring optimal inflation of tires under different situations and temperatures.

The inertia compressor is only 1" thick by 3" in diameter and weights a mere 8 ounces. Its expected design life is 130,000 miles, with ten years of battery power. The system has been shown at some past auto shows in the U.S., installed in the Grand Cherokee Concierge prototype concept car.

Just some random stuff about the actual TPMS:




Good wealth of information DMB

while i agree that this is a usefull feature if you want it, it can also be a real PITA. There should be a way to disable the system in a situation such as airing down the tires. When droped to 18-20 psi for traction the system beeps and displays a message in the message center. hiting reset clears the message temperarily, but it continues to come back with another beep and message. After 8 hours of being in an aired down state this REALLY starts to get on your nerves.

The problem with allowing people to air down is that is sometimes a way for the TPMS Module/Computer to see that it is time for "relearn" process. There a few vehicles out there that when you aggressively air down the horn will beep and there is a certain way to go about relearning for that vehicle. So if someone is airing down and the horn beeps and he goes about his business, he's goin to have a huge F*-Up.

In '07 it's suppose to be manditory on all US Vehicles. Some are making it state inspection. It's a great feature, for someone that wants it. With the way the world is now with customizing and accessories - manufacturers and aftermarket are now butting heads.


I would love to know how to go in with a computer or whatever to deactivate the system -- I bought the 17" chrome wheels that come on the 06 Limited for my 06 XLT- No sensor on the new wheels- Now I have to hit reset every time I start the car and there isn't a tool to take the sensors off the old wheels and put them on the new - You have to buy new sensors at $70.00 a rattle

The sensors are actually easy to take off, but you have to break down the wheel/tire and get the tire somewhat off the wheel and then get the sensor. I have a feeling the sensors are the same (for the stock wheels and limited wheels) you just have to make sure. I wish you were closer cause I could help you out.


Drew -- Thank You -- When I ordered the XLT I then went to parts to order the chrome wheels that were only available on the Limited or EB (311.00 a piece )
No sensors in them and didn't know that I needed them -- Bought 275-60-17 Tires
and had the whole works put on the XLT - What a difference - Now I've got the 24/7 Low Pressure Alarm that has to be reset when you start the car - Don't have a problem with having the tires taken off but I wish there was more info or a take off and remount tool so I could take the tire guys thru the procedure - I'd like to keep the integrity of the car so that if someone else drives the car they don't think they're getting a flat-- And now you have the WISEGUYS - Nice tires Frank-Wanna push the reset and kill the tire lamp on the dash ---Thanx Again

Think, "cost benefit analysis"'s not worth it.

Just more things to go wrong and cost me more money to repair.

Typical.....liberals in government.....want me to pay.....cause, they think I'm not smart enough to check my tire pressure. So, they mandate the auto mfn to put that (TPMS) in.

Aloha, Mark

Damn shame there isn't an easy way to disable the TPMS -- I don't have the dash with the menu in it (2006 XLT) I'm told you can disable the system with that dash - I think the EB or Limited has it

Well in 07 you probably won't be able to disable it (easily atleast) because it will be mandated by the government.


Very interesting thread. Got my 006 Eddie on Sat., and it´s equipped with TPMS. ( I´ve ordered a 2006 XLT V8, don´t know who is responsible for shipping a V8 Eddie to GE, but I´m not mad on it ;) ).

Only prob : I want to use the 18" plastic-chrome-covered-wheels only for winter, for summertime i´m interested in Cragar-Wheels with a little wider tires ( 275/60 17 or 255 /60 18 ). Does anybody figured out how to disable the TMPS, or where to get aftermarket-sensors that fit the Ford-TPMS ?

I haen´t found a fuse esp. for the TPMS and I´m not sure if it´s embedded on the EEC / OBD...

It uses it's own computer like a brake module (ABS). Right now, no one on here has found a way to disable it. My best advice is to get ford 17s and put their sensors on there and then learn them to the transmitter in the vehicle. TPMS will be hard to get around til aftermarket companys find a way. As of to my knowledge, everyone in the aftermarket world is still developing wheels.

Also, it's not only the wheels that are cause problems (cause the sensors have to sit flush against the wheel), its the people that want to use 22s and have hardly any tire/rubber on the sidewalls. You know how you bend a wheel? Well when you hit the curb or pot hole or whatever else, you run the risk of snapping that sensor and buying yourself 80-100 sensors every other week.


Drew, I still wonder why they put a TPMS on a SUV / CrossTerrain-Vehicle... Would have made more sense to give the driver the choice of enable/disable this feature for using Non-TPMS-wheels. But like wie know : that´s the way to sell parts.

Granted - but with the %'s of Explorers out on the roads, they are found more in grocery store parking lots than desert terrain. See what I'm saying? To them it's more practicle to have it than not. Plus by 07 it is mandated in the US. So they are trying to get any kinks out as possible


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I know, Drew.... it´s the same like the "Big M.´s" CoffeeCups : "content may be hot"...

But in GE we´re going close to that, just a matter of time. It´s not really fun anymore over here, it I would be a little younger or a good job-offer over there... Wouldn´t take much to make me move.