Q: Imagine you are driving down a crowded highway with cars all around you. How does your car’s computer know your tire pressure from the car next to you?
A: With your car’s TPMS.
What is TPMS and what do I need to know:
1. TPMS (Tire Pressure Monitor System) is a small electronic device that is mounted inside the your tire wheel rim that talks to your car’s computer. The TPMS sensor is attached to the valve stem in each wheel rim. It measures the tire pressure and if/when the tire pressure drops 20% from “reference” it sends an alert to your car’s computer that the tire pressure is low. We’ll talk about “reference pressure” further down.
2. Most TPMS sensors (one in each tire) are battery powered. The batteries are good for 5-10 years, 8 years on average. You have 5 tires (4 on the car and one on the spare tire.
3. TPMS sensors were mandated on US cars in 2007. Reason, remember all those Suburban’s that were having blowouts and rolling over about 10 years ago. It was because car owners were not checking their tire pressure. Pressure dropped, tire overheated and blew out. Heavy vehicles are the most prone to blowouts. The 2007 mandate was to alert drivers who didn’t know to check the tire pressure once in a while. So, the government decided if drivers weren’t' going to check tire pressure they would do it for you. Why does tire pressure drop? Oxygen molecules are very small and will pass through the wall of a rubber tire! (yep, it's true, look it up). ANY tire will lose about 10% air pressure every year. Filling tires with nitrogen will help greatly because nitrogen molecules are much larger and will not pass through the wall of the tire. Low tire pressure will cause a lot of rubber flexing and heating. Enough heat will cause the rubber to get soft and blow out. A tire filled to 33 psi will drop to about 25 psi in a couple of years and then watch out!!! A heavy vehicle like a Suburban, SUV or Van is cruising for trouble.
4. EACH TPMS sensor has a serial number (code) that is transmitted whenever it sends out a signal. You must tell your car’s computer what codes to listen for (you have 5 codes including your spare tire). If you replace any of the TPMS sensors in your tires you must remove the code in your car’s computer and replace it with the code from the new sensor. The code numbers are printed on the outside of the new sensors you install. BE SURE TO RECORD THE CODE NUMBERS BEFORE YOU INSTALL THEM IN YOUR TIRES. (Imagine you are driving down a crowded highway with cars all around you. How would your computer know your tire pressure from the car next to you. It’s only because your computer knows the codes of the sensors on YOUR car.)
5. Many people have summer driving tires mounted on rims and also have winter tires mounted on rims. When the seasons change they swap tire/rims. With each swap you will need to tell your car’s computer the CODE for the TPMS sensors you just installed on your car with the latest tire/rim swap. Car dealers and tire centers will usually charge about $20 per tire to reprogram you car computer with these new codes ($80.00) each time. Some tire places will also charge this to rotate your tires (see more below).
6. If you install “generic” TPMS sensors, you must also tell the TPMS sensor what kind of car it is being installed into. Reason, computers in different make/model cars use different programming protocols, so you need to tell your TPMS sensor what kind of car it is going to be talking to (Ford, GM, Toyota, etc.). You will also need to program the car computer with the codes it needs to be listening for. You will need a “special” device for this programming function (see below).
7. Also, you may need to reset your car computer “TPMS system” from time to time. What is a “reset”. While your tires are cool, fill them to the air pressure you want. Most people use about 33 psi, I use 38 psi. Once they are all at the level you want you then “reset” the TPMS computer. During reset the computer records the pressure of EACH tire and then if the pressure drops 20% or more your “low tire pressure” light will light up. How do you “reset” the computer. I looked it up in my owner’s manual. Under the steering wheel below the dash completely out of sight is a tiny button. You turn the car on, stand on your head so you can see the little button and then hold the button until the “low tire pressure light” flashes 3 times. You can’t see it flash because you are standing on your head so you might need some help with this. Then you wait several minutes while the computer takes a reading on each tire and that become the “reference” pressure. Pretty slick. My Avalon just has a single "low pressure" light. But some cars actually display the pressure of each tire on a heads up display. If you rotate your tires you need to re-program your car's computer and tell it which code goes with which tire, because you moved the tires around. This is NOT a reset, it's a re-programming function so you will need that “special” device mentioned in step 6. This is why some tire dealers charge quite a bit to rotate tires.
8. SO, I did some research and came up with this list of “stuff”. See links below:
9. Most TPMS sensors are about $50 each. I found this set of 4 generic sensors for $110. These are made to talk (protocol) to a Toyota Avalon, 2011. You’ll have to find the correct one for your vehicle. Set of 4 TPMS sensors $110: https://tpms247.com/products/set-of-...nt=20950975941
10. I found this "inexpensive" programming tool for $119 to program your TPMS sensors and car’s computer. There’s even a video on how to use the tool. You could probably buy the tool, use it and sell it on eBay for $80 and you'd be in good shape and only out $40 or so.
11. OR, you might go the $6.00 route and just replace the valve stems with these red/green indicators (see links below).
12. Programming Tool $119.00 here or $129 on Amazon - ATEQ Quickset TPMS Reset Tool:http://iapdirect.com/ATEQ_TPMS_Reset_Tool_Quickset.html
13. How to use the tool video: ATEQ Quickset TPMS Reset Tool :
14. List of vehicles can I use this tool on: https://www.ateq-tpms.com/wp-content...11.16-V5-1.pdf
15. OR you might consider going this route for $6.00: https://www.amazon.com/gp/product/B0...HX7BFSIP&psc=1
16. Why did I do all this? My car is 7 years old now and I need new tires. The batteries in my TPMS sensors will probably fail before the new tires wear out. The tire dealer wants : $200 for 4 new sensors, $20.00 each to install them and $20 each to program them into the car’s computer. That’s $360 to have the computer tell me when my tire pressure is low. But, I already know to check my tire pressure from time to time so I don’t really need this expensive government mandated feature. I think I’ll go the $6.00 route and save the $360. But, I though you might like to know what I learned and how I could potentially reduce the cost from $360 to about $150 if I was willing to sell the “tool” on eBay for $80 after I was done using it. Hope this was educational and helpful to someone.