TPMS - Tire Pressure monitoring system - a learning experience

[gll99]

Don't laugh at me for being uninformed but I owned my previous car for over 15 years. It still only had 130,000 kms when I parted with it. I've never had a car with TPMS or discussed TPMS systems with anyone and it only came up at the time of a new vehicle purchase.

Last month I bought a new 2015 crossover suv and it came with TPMS (Tire Pressure Monitoring System). When I asked how it worked I got different stories.

The salesman said the sensors were attached to the rim with a wired connector going to the vehicle's computer and display. He said if I reused the rims I could buy new winter tires and the existing sensors would work fine as long as I reused the original rims. (Not really true and I also couldn't visualize a rotating cable connected to the axle and rim but then I've never owned a vehicle with those.) Anyway..... I then got conflicting info from their service rep a few days later when I called about buying winter tires. The service guy who answered the phone correctly said it replaced the valve stem in the tire so technically was attached to the tire but he couldn't explain how the info was transferred to the vehicles display. He then said the sensors couldn't be successfully transferred to the new winter tires with the original rims so I would have to either buy 4 new sensors at about $100+ each or go with regular valves and ignore the warning light. I decided to wait a bit since I couldn't see spending over $400 twice a year to swap out 4 sensors. That didn't make sense to me. ( This info by the service rep was incomplete and not quite true ). The sensors can be reused but there is a risk of damage. Remember their standard procedure is to destroy the old valve and use a new one when installing tires on old rims. It's faster for them and less risky for leaks. So I can see why they do not appear eager to delicately save a sensor valve combo.

Jump ahead 4 weeks later to just a day or two ago when I decided to buy 4 new rims and 4 winter tires from the same dealer so it would make for an easier spring / winter switchover twice a year. I called their parts and service departments for a purchase and install appointment. I spoke to 2 different service reps and was told to just go with regular valves for the winter and ignore the warning light. That way it would be a simple tire mount each change of season and the sensors would work all summer with the original rims and tires. So that's what did. I was in the quick-service bay (Saturday) with the young fellow when he installed my new tires which had already been mounted and balanced on the new rims and I asked him if there was a special connector at the axle. He said no he saw no connectors it was just a regular wheel swap. I took my summer tires and rims with me so they put them in the rear of the suv (They are still there as I type this).

Here's the funny part:

When I drove home I fully expected the warning light to come on but it didn't and the TPMS display showed that the tire pressure on all 4 tires was ok. That confused the heck out of me at the time since I only have regular valves and no sensors on the new winter tires.

Good old youtube to the rescue:

http://www.youtube.com/watch?v=ZhOcYH-hrm0

The sensor has a battery and radio frequency sender built into it. The sensor info is sent wireless!

After watching this video it dawned on me. (Cue the lightbulb) This means the computer was likely receiving the signal from the tires in the trunk area of my suv. Great safety system right I fully expect the light to start flashing when I remove the tires and store them in the basement. That's one way to beat the system just drive with your old inflated tires in the trunk.

TPMS is not that new but I think I can be excused for not knowing how it works. I'm not so sure about an established dealership which shall remain nameless. So much misinformation and lack of knowledge. This should have been pretty easy to explain to me the customer by the dealer.

[redwudz]

I have a similar system on my car also. If someone decides to rotate the tires position, it will also give wrong information about which tire is low. Something to be aware of, but most tire shops and all car dealers should know this.

A newer system out, on I forget which car, gives you actual pressures on each tire and when you re-inflate the low tire, it beeps the horn when the pressure is correct. That's impressive.

[gll99]

Aside from the trouble light my vehicle has a display screen that can show a variety of selectable items. One of these is an overhead image of the vehicle with the tire pressure reading showing next to each of the 4 wheels. It's supposed to be a standard feature in all the new models.

Apparently on my suv when the system senses a fault it doesn't correct immediately when proper inflation is restored. According to my user guide it can take many many miles before it resets. There is no relearn/reset button or sequence that I am aware of except just to drive the vehicle a long time after a change.

One bad thing is that the batteries in the sensor are not replaceable and when they fail the sensor is done. Canadian winters are pretty cold and extreme sun / heat kills dry batteries too so I can't see how the batteries can survive the 4 - 5 years they are supposed to last. A much simpler and less costly system could have been designed. This looks like planned obsolescence to make money for the car repair industry. I didn't think much of it when I first heard it was on the car. Seems to be more of a pain than it's worth. I heard it's mandatory for manufacturers but it will be worse if it becomes law for safety checks as it supposedly is in some States in the US. There will be no ignore or black tape over the light option if it becomes illegal or an insurance issue.

[TreeTops]

Much thanks to gll99 and Redwudz for that info. I have always wondered how TMPS works. I have also had conflicting responses to my questions about that system.

[gll99]

Have visitors watching CFL today so the summer wheels are still in back of suv. Will report which tire if any my car says is not working as I remove them 1 by 1 later today or tomorrow. Meanwhile Wikipedia has interesting information on different TPMS:

http://en.wikipedia.org/wiki/Tire-pressure_monitoring_system

It's an ongoing education.

[TreeTops]

Too bad we don't have a chart of which manufacturers use which system.

[ranchhand]

Thanks gl99, good topic. I didn't know the sensors were wireless, and now I have the battery & valve to replace when it dies in each wheel. Great. Anyone got an idea what these things cost in the USA?

[hudsonf]

Thanks gl99, good topic. I didn't know the sensors were wireless, and now I have the battery & valve to replace when it dies in each wheel. Great. Anyone got an idea what these things cost in the USA?

http://www.amazon.com/b?node=2201763011

[zzyzzx]

You should have done your homework before buying the new tires/wheel sets. Anyway, my car uses the sensors for the anti-lock brakes for the TPMS so I don't have to worry about this stuff since there is nothing in the tires for this.

[gll99]

@hudsonf
Based on the Amazon prices you linked to my dealer quoted a near 400% retail markup on the sensors. Lets hope that included some type of extra installation and wheel by wheel calibration fees otherwise it's really excessive.

Too bad we don't have a chart of which manufacturers use which system.

That's a good point. It would help to know how they work. I did a Google search on my vehicle model and TPMS and got some info but it's not the detail guide I was looking for.

You should have done your homework before buying the new tires/wheel sets. Anyway, my car uses the sensors for the anti-lock brakes for the TPMS so I don't have to worry about this stuff since there is nothing in the tires for this.

I was in a bit of a bind to make a purchase and chose the vehicle 1st before I even knew anything about TPMS so it was the least of the considerations. After that I didn't have much time to decide on the winter tires but by the time I bought them I knew it was a case of paying $400+ for sensors or putting up with a "1/2 tire diagram" light for the winter months. I just had never seen the light so didn't know how intrusive it might or might not be. Yours might possibly be the ideal type at 1st glance but if they are Manufacturer / model / vehicle specific it would be a weird way to choose a vehicle based on its TPMS.

=============================

An update. It took a while because I haven't driven much.

My original belief was that the internal receiver was possibly reading the tire sensors from my summer tires in the back compartment of the suv and that's why it was reading as "ok" and showing good pressure on all 4 wheels even though the new winter tires on the suv do not have sensors. It turns out that it's not that simple.

I removed the original tires from the trunk space one by one but kept getting the same "good" readings when I checked with the vehicle in the "run" position but not started. After that I read that my vehicle checks the pressure every time it starts but that too showed the tire pressure as "ok" with the tire pressure showing on all 4 wheels in the pictogram. Later I read that on some systems it only activates the TPMS while the wheels are rotating but that too didn't change a thing and I still got a good reading even though I had no sensors anywhere near the vehicle.

By this time I had only driven a couple of short trips since my winter tires were installed roughly a 10km and 5 km trip. since then I drove another 2 short trips and just as I got near home the last drive I heard two dings and a message popped up on the display screen "Tire pressure monitoring system needs servicing". Then the display returned to normal and a small separate yellow bottom 1/2 tire shaped light came on. When I switch the screen to view the vehicle pictogram it shows no tire pressure next to each wheel in the image. That's not an issue because I don't see that screen unless I call it up. The yellow light is not distracting at all since it sits in a dark area by itself outside the normal analog and digital screens and gauges. It will be easy to tape out if I decide to do that but I doubt I'd even notice it while driving unless it starts some type of dinging and flashing cycle or something.

Lets hope the mileage it took before noticing the sensors were not reporting is not indicative of the time it would take to sense a flat tire condition. If so it would be useless driving 25-40 kms on a low/flat tire.

[redwudz]

From what I've learned, if you have your tires rotated, the sensors or the car computer on some vehicles may need to be reset to read the correct tire location.
A few car computers can do this themselves, but most need a external tool that a modern tire shop or car dealership should have. They are a bit expensive for home use. Some of them are shown in hudsonf's Amazon link.

My Ford Fusion just has a warning light that doesn't seem to tell me which tire might have low pressure. No idea if rotating the tires needs a computer reset with my system. Something to ask my dealer at the next servicing.

With snow tires and rims, even if you placed the correct TPMS sensors in the rims, you would still likely have to reset the car computer, then once again when you removed them if individual tire locations are shown in the dash display. $$

You could call your car dealership or a tire shop and they could probably tell you the cost of this and if it's needed. I would think with newer vehicles in snow country this would be a fairly common procedure.

A bit more info on the TPMS sensors: https://en.wikipedia.org/wiki/Tire-pressure_monitoring_system

A Q&A short version: http://www.tirereview.com/common-tpms-service-questions-and-answers/