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
-- 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.
-- 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).
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.
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:
- 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
-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.