TPMS - Did its Job?

Discussion in 'Clarity' started by MrFixit, Apr 29, 2022.

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  1. MrFixit

    MrFixit Well-Known Member

    I wanted to reflect on a recent TPMS experience. While driving along, a TPMS warning appeared. Naturally, worrying about a flat, I stopped to check out the situation.

    First problem - The TPMS (although I am certain it knows) does not provide any clue as to which tire(s) may be low. So, I go around checking all the pressures and sure enough, the rear driver's side tire was low (around 28 PSI). The others were all very close to the desired 36.

    I examined the visible tread area and didn't see anything or hear any hissing. So, I filled it back up to 37, and started driving again.

    Second problem - Even though the tires were all back to nominal pressure, the TPMS warning persisted. The vehicle latches the TPMS warning and it will not go away until you perform a TPMS calibration. This is a problem because I had no idea whether this was a slow leak, or a fast one... I did not want to do a TPMS calibration without further knowledge because doing a calibration while the tire is leaking is a bad idea. It should have used the previous calibration (and removed the warning) until I chose to re-calibrate it.

    So, without any additional help from the TPMS system, I had no choice but to repeatedly stop and re-check the pressure of the bad tire in order to know how badly it was leaking. After doing this 3 or 4 times and arriving home with essentially no loss of pressure, it was clear that this was a 'slow' leak.

    I removed the tire which allowed me to thoroughly inspect it, and was able to easily find a nail:

    I could see why this leak would be slow and it looked to be easily repairable. I took it to the local tire shop and they patched it just fine. Now, at this point, it was OK to re-check all the inflation's and do a TPMS calibration.

    Here is what irks me... The whole principal of this TPMS system (where it doesn't measure the tire pressures, but rather, looks for rotational difference between tires) has been questioned before in this forum. Be that as it may, Honda failed in mechanizing this system. With no additional cost (only a small software update) the system could easily report which tire is at fault. Also, if the fault goes away (ie: you add air pressure), why not clear the indicator to be able to perceive additional air loss while it doesn't make sense to do a calibration without identifying what the root problem is?

    Yes, it detected a real problem - and I am grateful for that. It could have been much more useful however.
    insightman and gedwin like this.
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  3. Robert_Alabama

    Robert_Alabama Well-Known Member

    I can find the oem "TPMS" to be bothersome for the same reasons you described. I added this item to my car and love it.
    I have a couple of battery packs that will never shut off and every couple of weeks I swap the one supplying the display and recharge the other. I guess you could argue that's a pain, but I've gotten used to doing that. Anyway, for me I really like being able to see the tire pressures.
    Frankwell likes this.
  4. vicw

    vicw Active Member

    The lack of TPMS ability of the Clarity to report which tire has low pressure was probably my first big disappointment on the Clarity.

    I had assumed that capability was a given these days. I installed the same device as @Robert_Alabama did and have found it invaluable. I'm paranoid about the lack of a spare on the Clarity, and I want prompt reporting of any loss of tire pressure. The device isn't perfect, especially regarding battery drain when left ON and in the dark, lacking solar charging, so I habitually turn it Off every time I park in the garage on outside in the dark, and ON again when I start to drive. The alternative battery pack might be a better solution.
  5. JFon101231

    JFon101231 Active Member

    Agree with you it seems silly, especially since my other vehicle is a 2015 GM truck which shows individual tire info updated nearly real time
  6. Frankwell

    Frankwell Active Member

    Not to go too far trying to defend Honda's rationale, but since the system compares and records the rotational differences between the four tires, and then looks for changes in these differences that exceed a certain value, it's possible that they feel that while the system can detect a possible problem they don't feel confident that it will always be able to identify the problem tire. And similar thinking when you add air to a low tire after filling it, probably the rotational difference won't be exactly what it was at the last calibration since all of the tires may have lost some varying amount of air over time, so they don't want to just make the assumption that if it all looks good then it all must be good. Instead they want you to recalibrate, since that's easy to do. Now you have a valid point about the "moving target" when there is a faster leak, I guess the best approach is to fill the low tire, calibrate, then as soon as calibration is complete pull over again (when safe) and check the low tire again, if it's already lost pressure then you now have an idea how fast the leak is, but if has lost little or no pressure then you know it's a good calibration that did not get distorted by a faster leak and so the system should be able to let you know during your drive home if the tire later loses air. A hassle, but maybe the best that can be done with this type of system, I don't know.

    If it shows tire pressures then the system uses sensors. One advantage of the method Honda uses is that there is no concern about sensors wearing out, or getting damaged by a tire shop. It saves Honda money in manufacturing, and potentially the consumer money. Although obviously another viewpoint is that that's being penny wise but pound foolish. Unfortunately probably the vast majority of consumers of any product tend to be pound foolish, and car makers and other producers respond in kind. Not that this makes it right, but we have seen that with virtually every safety product that has ever come out. The public was not clamoring for ABS, airbags, or before that even seatbelts from what I have read. It has almost always required regulation to get these systems into cars.

    I didn't want to have one on the dash so I got one that plugs into the 12V socket. It's tiny though and lacks some capability. I hadn't thought about using battery packs so I might try that when I replace this one. What happens if you plug it into the USB port? I realize it will lose power while the car is off, but will it initialize quickly enough when you start the car? Or is the concern that you might wind up driving off with a flat and do damage before the unit has a chance to initialize.
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  8. Robert_Alabama

    Robert_Alabama Well-Known Member

    @Frankwell asked "What happens if you plug it into the USB port? I realize it will lose power while the car is off, but will it initialize quickly enough when you start the car?"
    I leave it in basement parking a lot of the time. The internal battery for the TPMS display will run down after a few days (maybe it has weakened since I have had it for about 3 years). When the car is restarted, it will chirp and try to come on if it has been allowed to sit dead for awhile. It will do this annoying chirping and trying to start for far too long before it finally has restored the battery enough to stabilize. So the annoyance of that caused me to go the battery pack changeout route. I now have mine on the dash to the left of the driver display. You could stick one on the side of the console in front of where your knee would hit and I did that for awhile, then just decided to put it on the dash. The way the dash is made on that side, it is pretty unobtrusive. I have a flat thin usb charging "cord" that lays on the dash just over the display running from the flat spot in the console (where I keep the battery pack). I did buy the console rubber mat so things don't slide around when laid there.
  9. MrFixit

    MrFixit Well-Known Member

    For those of you who have the aftermarket pressure sensor systems...
    Does anyone have enough experience to gauge how long the coin cells in the sensors last?

    In the link that @Robert_Alabama posted, there is this statement:
    "it is recommended to replace the battery of the sensor in 3-6 months."

    I have a feeling that they last longer than this.
    It would seem like a pain to replace the 4 sensor batteries 2-4 times per year.
  10. Robert_Alabama

    Robert_Alabama Well-Known Member

    Mine use CR1632 cells. The originals lasted a little over a year. Haven’t replaced them again yet. But for me, at least a year for batteries. They are really easy to replace.
  11. vicw

    vicw Active Member

    One of the original batteries on mine failed after about 10 months of use, with the symptom of that tire just not reporting updates anymore, so the reported temps and pressure didn't change. Note the out-of-sync temp reported on the right rear in this pic.


    I replaced all 4 of the the batteries with fresh CR1632's, and they have been working for about 18 months since. I assume that the batteries they ship in the sensors may have shortened lives due to shelf time prior to installation. It looks scheduling replacements once a year is a pretty good conservative schedule, but with this first new set I'm going to just watch for the first failure.

    If you wonder what that fuzzy stuff at the top of the unit is, unfortunately the display doesn't change brightness between daylight and evening, so I added a black felt shield there to avoid bright reflections in my windshield while driving at night.
    Robert_Alabama likes this.
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  13. coutinpe

    coutinpe Active Member

    I also hated the native TPMS so I bought exactly this same device. The battery of one sensor failed after a couple of months so I replaced the 4 of them to avoid surprises. I noticed from the start that the system reported pressures way higher than what both my digital and analog probes reported (40 PSI for the device was 36 PSI for the probes) but I just got used to it and kept it at "40" on all four. Then one day I found my front right tire flat. I blamed it on me driving through a dirt road the day before, so I took the car to the nearest garage. They dismounted and thoroughly checked the tire but found no leak. They inflated and replaced the tire and I happily drove home (they didn't charge me for the work). Next morning I found the front right tire flat again. Then a light came up to my head and I swapped the front and back TPMS sensors after reinflating the flat tire. Then after a few hours the rear right tire had gone down to 20 PSI. It was the TPMS sensor somehow slowly deflating the tire. I have no idea if the dirt somehow got into the sensor to cause this but at plain sight there is no visible damage or soiling. Bottomline, I put back my original caps, there has been no more leaks, and the TPMS device and its sensors are peacefully sleeping at the bottom of a box in my garage... I guess I'll stick to the hated native TPMS.
  14. Robert_Alabama

    Robert_Alabama Well-Known Member

    I guess all things can fail. I ran one tire essentially flat because I didn't trust the OEM "tpms" and could not get the thing to reset after a slow leak. I like having another system that helps a lot to back up that one and gives me much more peace of mind than additional worry. @coutinpe , I like mine enough that if I had one of the sensors leak like you describe, I'd just order another off Amazon for $27, change it out and move on. I think that the odds of one of the sensors leaking is pretty small, certainly no more than picking up a slow leak of some other kind in a tire. I've been using 2 of these (one on my car and one on my father-in-law's Clarity) for about 3 years with no issues other than changing out the batteries.
  15. Frankwell

    Frankwell Active Member

    That's my concern, that there is no way to know if a sensor has failed. At least not on mine, and apparently not on yours, since it seems when the signal is lost it just perpetually shows the last known value. Although I notice in your photo that the picture of the car is missing the right front tire, so I thought maybe that's how it tells you that a sensor is out. But apparently the right rear tire is the one with the out of family temperature reading.

    I can understand the manufacturer might think it looks bad if the pressure reading keep blinking in and out due to intermittent signal weakness or interference. I would be fine with them displaying the last known reading for ten minutes or something. But after that it should indicate that it is not getting a reading from that tire. Otherwise you think you are protected when you are not. I wonder if there are some brands of these devices that do indicate if it's not getting signal a from one of the sensors.
  16. vicw

    vicw Active Member

    I agree that recognizing the failing sensor is not ideal or instantaneous, as we would prefer it to be, but it really doesn't take long to notice that the failing sensor is not not being updated, and that it's time to replace the battery.

    Worst case would be that a tire lost pressure, coincident with the failure of the sensor to update, but I think that coincidence is pretty unlikely, so I'm comfortable with the less than perfect design on this very inexpensive device. If anyone knows of another similar device with a more perfectly designed mechanism for reporting battery failure, I will be happy to buy it, as long as it is competitively priced.
    Robert_Alabama likes this.
  17. Robert_Alabama

    Robert_Alabama Well-Known Member

    I agree with @vicw above. I had no problems recognizing that I had battery failure. It took me more time to remember to buy and replace the batteries than it could have taken me to recognize that one had failed. I'd much rather have the added protection work 95+ percent of the time (allowing a gracious 5% the time for me recognizing a failure and getting around to changing the batteries) than to live without it 100% of the time.
  18. Frankwell

    Frankwell Active Member

    Is there a reason why in the picture of your display the right front tire is not there, is that supposed to indicate something? Or is it always like that?
  19. Frankwell

    Frankwell Active Member

    How long does it usually take to notice that it has stopped updating? How do you know when this has happened?

    I'm not saying that I question the value of using one of these sensors because of this, certainly it's better than having no information. I am questioning a software decision that I don't understand why they are doing it this way, and I'm wondering if all of them work like this or just some of them.

    When a signal from a sensor stops being received, their choices from a design standpoint are:

    1. Immediately stop displaying pressure for that tire.
    2. Stop displaying pressure after a certain amount of time has passed (15 minutes or whatever)
    3. Continue showing the last known pressure but indicate with some type of marker that the sensor has not been recently updated.
    4. Continue showing the last known pressure but with no indication that there is any problem with the signal.

    I would have expected them to select from one of the first three options. Although maybe not the first one because it probably wouldn't look good if the pressure keeps coming and going, which might be normal but would give the impression that something is wrong with the system when it isn't. And it would mean that much of the time when you look at the display you wouldn't see a pressure for one or more tires.

    In the second option you would know that the pressure is current even if not exactly up to the minute. And if the battery is getting weak or some other problem, you would know about it because after a certain amount of time had passed with no signal the measurement for that tire would drop out.

    The third option would be ideal because you would always be able to see the last known pressure, but you would also have an indication that it is not current. You could then keep an eye on that tire to see if the pressure eventually gets updated, if not then you know that the sensor is no longer working.

    I'm surprised that instead of one of the first three they instead seem to have gone with option 4 which in my opinion is the least desirable method. The next time I buy one of these I now know to research this particular detail in how they operate.
  20. MrFixit

    MrFixit Well-Known Member

    This is my biggest fear with this type of device. The problem is fundamental - These devices defeat the inherent seal used by all types of tires (the Schrader valve). They depress the Schrader valve (not unlike what your tire pressure gauge would do), and then they rely on an O-ring (or similar) to act as a seal. When one of them leaks like this, it is likely not a 'bad' sensor, but just the fact that the O-ring is not nearly as good as a Schrader valve. Changes in temperature, how tight you make it, the locking nut tends to work against a good seal if you use that... All of this is inferior to the tried and true Schrader valve which is very robust.

    This is part of the reason that the factory systems which measure tire pressure have the sensors installed within the tire. This makes them less accessible, and more expensive, but they are more robust and less prone to leaks.
  21. Robert_Alabama

    Robert_Alabama Well-Known Member

    @Frankwell asked, "How long does it usually take to notice that it has stopped updating? How do you know when this has happened?" I don't remember for sure, I'd guess a couple of times of driving. I know now to watch them as they fluxuate during the drive/day as the temperature changes. I may proactively change them when I get over a year on these batteries.

    @MrFixit said "and then they rely on an O-ring (or similar) to act as a seal. When one of them leaks like this, it is likely not a 'bad' sensor, but just the fact that the O-ring is not nearly as good as a Schrader valve. Changes in temperature, how tight you make it, the locking nut tends to work against a good seal if you use that... All of this is inferior to the tried and true Schrader valve which is very robust."

    These add on systems are also available with internal sensors.

    I shied away from this because I like the ease of the valve cap sensor flexibility even though it adds some failure risk. I keep two extra wheels that I use to rotate in new tires as I need them (I'll drop the wheels off at the tire shop with two new tires and get them mounted, then swap with the two I want to replace on the car, then rinse and repeat). With the valve sensors, this is not an issue.
    Last edited: May 1, 2022
  22. MrFixit

    MrFixit Well-Known Member

    I agree with you that ease and flexibility wins and the cap sensors are a better choice as an add-on like this. Upon occasion, if a cap leaks, it would most likely be slow AND the display gives you visibility so you will know that it is happening before it becomes a problem. It does seem prudent however that the valve cap would be a prime suspect with any pressure loss. It is probably good to do a soap bubble check whenever you install one of the caps and check the caps for leaks as a first step when a tire shows any sign of leaking.

    The internal version that you sent the link to has some very poor reviews.
  23. HK64_L

    HK64_L Member

    In my Hyundai Kona Premium EV the TPMS (tyre pressure monitoring system) shows a graphic of the four tyres with each measurement, indicating the pressure of each. In addition, every 4 - 6 weeks I check them with my t.p. monitor and 'clean' the tires (the 90% that are visible) to remove road stuff. This only takes 5 - 10 minutes.


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