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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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Ford vehicles do not all use the same system. Here's the TSB I found for the '06 Exploder:

FORD: 2003-2006 Expedition, Explorer
2006 Escape Hybrid, Escape, Freestar
LINCOLN: 2003-2005 Aviator
2003-2006 Navigator
MERCURY: 2003-2006 Mountaineer
2006 Mariner Hybrid, Mariner, Monterey

Vehicles built with the tire pressure monitoring system (TPMS) sensors may experience a concern where the TPMS indicator is on solid and the message center (if equipped) displays "Low Tire Pressure". This may be due to the actual tire pressure being low due to time or temperature changes (10° = 1 psi). Adjusting the tire pressure to specification should turn out the warning light once the sensors have been awakened.

If the vehicle has been stationary for more than 30 minutes, it will be necessary to wake up the sensors with the training tool to force them to transmit the latest air pressure information to the smart junction box (SJB), or responsible module. This can be done by either driving the vehicle for 2 minutes above 20 MPH (32 Km/h) or by using the training tool. The sensors do not continuously transmit when the vehicle is not moving.



Inflate all tires to the correct air pressure.
Place the ignition in the RUN position.
Use special service tool 204-324 for valve-mounted TPMS sensors or 204-363 for wheel mounted sensors.
Place the magnet on each sensor for approx. 5 seconds or ping each sensor at least twice after adding air to ensure the module has the latest air pressure data.
If the TPMS indicator does not go off after filling the tires to the correct air pressure and pinging each sensor then refer to the appropriate Workshop Manual symptom chart.

However.... Our pool car (05 Freestar) here at work uses a system that monitors the number of wheel revolutions and compares them to each other. If all four tires drop in pressure over a given distance, it won't see much of a variation, so it's possible for all four tires to go low with a temperature change. If one specific tire runs low, it'll notice it (and has). Resetting it is a simple matter of scrolling through te information menu and resetting the tire pressure to recognize the existing setup. We had to do that after we had the tires rotated last month. The owner's manual doesn;t tell you how, but I found it online. :)

I'm not a fan of the in-wheel sensors myself. Too many freakin electronice to tell you you're an idiot. I'll stick with an old-fashioned tire pressure gauge. :)


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I have always had faith in my tire guage !!! Bought an 06 XLT -- Changed the wheels to Ford Linited Style-Chrome (311.00 a piece) Now I've got a 24/7 tire pressure alarm because the New Wheels have no sensors - Wish I could find the procedure to just disable the damn system - Tired of pushing reset every time I start the new XLT-
Been to 2 dealerships and no one knows how to take the sensor out of my 17" optional aluminum wheels and install them in the Ford chrome wheels. No one seems to know how to get the steel band that wraps the rim inside off and re-install them on the chrome wheels. It's a Ford wheel - Come On

I have an idea for this problem, at least the airing down part. If you can make them "re-learn" or recalibrate them, and there is no high pressure alarm, Why couldn't you just air all of the tires down to almost nothing, do the re-learn procedures, then air them back up?

Then the system would be fine if as long as yo don't air them down below what you aired them down to for the re-learn.

Would this work or is there a fail safe for this?

The relearn part is to tell the computer where which tire is. If you do a rotate and balance and dont relearn the system -- when it says "right front tire low" it actually means the right rear because you didn't reset it. The transmitters are wheel specific for that reason. Relearn has nothing to do with setting the tire pressure (atleast not what I have heard).


(un) real world of bureaucracy

This thread has been sitting silently for the last couple of days, so I thought I would add a little stirring to it.

This has been extremely interesting and prompted me to go a little more reading on what the idiocrats are up to.

First a comment that has been stated during the thread but never explicitly - these direct systems are just like our old oil pressure systems. They are not really a pressure sensing 'system' - they are merely a switch that is preset to bring an idiot light on when the pressure drops below its setpoint. I guess the engineers couldn't float the extra few pennies past the bean counters to actually get a pressure transducer installed.

Next. Here is a link to an industry site that is not very happy with the proposal. I won't editorialize on their position as you are capable of making your own decisions. However, I will point out one area that you might ask yourself if it will ever apply to your (or your family's) driving. It is the part about what the NHTSA has EXCLUDED from its testing procedures for system certification. I know for sure that it will never be over 104 F or below 32 F on the road surfaces here it West Texas so I am not concerned at all with the exclusions.

Could you post a link to the website that is designing the autopump system? As for the tire pressure monitor, why can't they make a small sensor that just screws on in front of the tire valve that is a little bigger than a cap? Is the reason because they can't design one that small, or because they are afraid of them getting stolen by somebody just coming along, and unscrewing one of them? The internal one is good, but requires removing the tire to replace it. This one is easy to replace.

Little bit of an update:

I was at the '06 Motor Trend Auto Show here in Richmond, and I noticed that A LOT of manufacturers had TPMS on their vehicles. The cars were mostly 2006 models, but some were '07. I believe out of the whole show, I only saw a few with rubber valve stems. Looks like it's here for good


And I read a Ford TSB about the TPMS. Even on the 2006 Explorer different kind of TPMS-Sensors are in use, different body colors ( orange, blue ) - and you cannot mix the sensors.

So, what the heck are they doing ? I´m going to buy some dummys fpr my summer-wheels that only sends a "tire good"-signal, independent from the real pressure. I don´t have any zest on searching the right ones over here in GE, where nobody knows the system himself.

I´m already pissed on with my tires : got one flat, and had to pay 480.- for two new tires ( in GE you mustn´t run different tires on one axle ). In the states the tire warranty would have eased my trouble, over here you´re simply lost. : (((

Can anyone confirm that one can deactivate the TPMS on a 2004 Explorer Limited? All of my alluminum wheels have corroded from the inside and created varying levels of leaks in all my tires. One leak ( front passenger side) is so severe I have replaced it with the spare. Having grown weary of consistently having to put air in my tires, I have ordered new wheels. ( I have made my Ford dealer aware of my situation... they referred my circumstances to a rep who determined nothing could be done because I have exceeded their 36,000 mile warranty. ( I have just turned 40,000 miles). I really didnt expect to have to make a $700 investment in new wheels 2 years out from purchasing a $40,000 vehicle. But I digress. I think I recall seeing a read out from the message center stating: Tire Pressure System - enabled -
Of course, now with the spare on all I get is the - Tire pressure very low-warning light.
If I put the bad wheel/tire (after inflating it) back on will I be able to disable the system so that when I put the new wheels on I won't have to deal with the erroneous warning message?

Thanking any respondents in advance...


To my knowledge, there is no way to defeat or disable the system. It's integrated into the Smart Junction Box, the modern equivalent of the earlier GEM modules. Essentially the SJB controls just about everything electronic on the vehicle. It's *remotely* possible that a dealership may be able to toggle the feature on or off when connected to the computer, but I'd be surprised if any dealership would be willing to open itself up to the liability doing so presents.

I think, for the moment, you're basically SOL on that front.


I'm sure the aftermarket will be along in the next couple of years to combat that. Unfortunately, with the current lack of industry standards with regards to tire pressure monitoring systems, aftermarket will be slow to respond due to the wide variety of systems used.


They may do it for 2006 or earlier models, but for 2007+ it is mandated by the government and they'd be in a lot of trouble if they disabled it, you had an accident with a blown out tire. That's a bad situation!


Found some interesting information for the ones who want to disable your system:

Tire Pressure Monitoring Systems (TPMS): In April 2005, NHTSA issued a final rule that requires all passenger cars weighing 10,000 pounds or less to have tire pressure monitoring systems (TPMS) by model year 2008. Vehicle manufacturers will be required to install a system that can detect when one or more of the vehicle’s tires are 25 percent or more below the recommended inflation pressure. The new safety standard, Federal Motor Vehicle Safety Standard (FMVSS) No. 138, will be phased in starting on September 1, 2005. 20 percent of MY 2006 cars will be required to comply with the rule, increasing to 70 percent of MY 2007 cars, followed by 100 percent of all MY 2008 cars. While the rule is technology neutral, NHTSA estimates that the new systems will cost the OEMs between $48 and $70 per vehicle using systems currently in the marketplace. While NHTSA anticipates that the TPMS system will work with most replacement tires and aftermarket tire/rim combinations, the companies selling and installing such products are exempt from the “make inoperative” prohibition if the TPMS system does not work, so long as it is after the first sale. (The TPMS must work for dealer installations occurring prior to first sale.) Nevertheless, it will be illegal for anybody to disable the malfunction indicator light on the dashboard. SEMA received confirmation from NHTSA that equivalent aftermarket TPMS that meet the safety standard may be installed on the vehicle. SEMA requested that the TPMS be reprogrammable in order to accommodate alternate and replacement tires with different pressure thresholds. However, NHTSA did not see a need to mandate reprogrammability or service information sharing since the agency believes this will occur naturally in the marketplace, without regulatory pressure.

Not that I support doing anything illegal - but I wonder what the fine is for disabling your TPMS. Probably pretty hefty since it's a safety issue.


AFAIK, the law only applies to the first sale of the vehicle by the dealership, and deactivating the indicator on those vehicles that require it (i.e. NOT the '04 or '05) is still illegal.

However..... You may still be able to fool the system legally as a consumer. Fooling the system into thinking the TPMS sensors are in the wheels isn't explicitly prohibited, so I'm sure there will be systems around soon that can substitute the wheel sensors the same way the Oxygen Sensor Eliminators fool the emissions system into thinking everything is fine even without catalytic converters.

This is my favorite though:
However, NHTSA did not see a need to mandate reprogrammability or service information sharing since the agency believes this will occur naturally in the marketplace, without regulatory pressure.

Yeah, right.... like every brake shop can pull the codes for the ABS system, or every shop can diagnose anything GEM related.... Just another prime example of how thoase that make the laws for this country just don't have a clue!!


Can you do this yourself, or do you need a special magnet from ford?

I did it myself with a couple of strongs magnets and it worked beutifully.

Can you explain what exactly you did ?

Yesterday I had a '06 Jeep Commander and the information center said "all tires are low". The tire pressure was 30 psi where the door said 35 psi. These systems are getting more "picky" with more time. That's a 15% change in tire pressure that the computer didn't like. The vehicle was recently at a Jeep dealer, all tires, including spare were at 30 psi. The spare was even at 30 psi (it was a full size alum. rim spare).

Just wanted to share.


Just to chime in, I have had the aftermarket Smart-Tire system on my 2000 Mounty. Been using it for almost 2 years. It was a little pricey. But I thinks it's great, and worth it. I give it a definite recommendation

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Mace - please put a review in the review section of the forum. That would be great! Some pictures would be awesome!