Mace1647545504 Posted July 27, 2020 Report Share Posted July 27, 2020 I have an 03 M3, I bought it on BaT. A few days after I got it while driving the tpms light kicked on and yes 1 tire was low. I added air, reset the light and took it home Took it out again and after a while the light kicked back on. THhs time I took it to discount tire, they looked and said the tires were 10 years old. They took it off checked it to ensure there wasn't a leak, refilled it , i reset the light and went home. Yep you guessed it the light came on again after driving for a while(as usual). So I got tired of f'ing around and bought 4 new tires...reset the light and drove it home. Heading to cars and coffee a few days later, the light came on and I took it back. They measured the tire pressure and found 1 low. They took the tire off dunked it and said it was leaking in 4 spots. The tech said it must not have sealed well. He took the tire off roughed it up and put it back on. I took it to c&c, on the way home yeah you guessed it tpms light. So I called them and they said they would replace the tire, BUT just to be sure it wasn't a rim I took it to wheel medic, they checked it out said the rim was in great shape and stated that it could be a wheel sensor misreading what was going on. I have..well the original owner put spacers on the wheels I asked it those could be the issue and was told no. So I have a really good mechanic but all I've had him work on is my american cars. Will he be able to tell if it's a wheel sensor ot will he need some special german reading tool to determine this or should I just bite the bullet and take it to someone who services bmw? Sorry for the novella . Quote Link to comment Share on other sites More sharing options...
gillbot Posted July 27, 2020 Report Share Posted July 27, 2020 But a new tpms sensor and have it installed? Quote Link to comment Share on other sites More sharing options...
TurboRust Posted July 27, 2020 Report Share Posted July 27, 2020 sounds like the sensor is doing its job if the tire is low every time you check. so let them replace the tire and see if you still have issues. Quote Link to comment Share on other sites More sharing options...
Mace1647545504 Posted July 27, 2020 Author Report Share Posted July 27, 2020 there is no tpms sensor on the car apparently it uses the wheel sensor just put a new tire on and after a few mile the light kicked again Quote Link to comment Share on other sites More sharing options...
mmrmnhrm Posted July 28, 2020 Report Share Posted July 28, 2020 Ya... cheap TPMS by comparing wheel rotation speed is a thing. Another possibility is if you have a fifth wheel rather than a doughnut for a spare (e.g. wifey's 2008 RAV4), there's a sensor in there as well that could be unhappy. Quote Link to comment Share on other sites More sharing options...
Trouble Maker Posted July 28, 2020 Report Share Posted July 28, 2020 As Derek said, if the tire is actually low by you checking with a tire pressure sensor, then the system is doing it's job. If WSS (wheel speed sensor) based, does it somehow auto learn if you change the condition (tire, inflation, ballance, etc.)? On some cars you have to reset the system, so it can learn the new situation. I'm not aware of any that can auto learn without user intervention but it seems possible. These systems look at the vibration/frequency spectrum of the WSS signals. Just a general example of what the 'raw' signal over time VS frequency spectrum of a signal might look like. Those peaks on the right are the (frequency) characteristic of whatever thing this is. So if something about that thing (system) changes, then that right side graph will change. If it goes outside of 'normal' or so different than the others then the tire could be inflated incorrectly (high or low). But 'normal' is different for every tire/wheel, every balance, or even if you change the inflation pressure. So the system has to relearn what is normal. Some of them do this by having you reset button for you to hit (sometimes a real button but sometimes soft button in some HMI). If you don't do this, it can definitely cause false positives. We went to some sand driving and aired down, then aired back up as soon as we got off of trail. Then when we left that camp ground the next day and drove on the highway* the system triggered. *Many of these kinds of detection systems also require fairly constant driving conditions to detect. Large varied speed (big acceleration or deceleration), big lateral inputs or rough roads will not allow them to work correctly so the systems ignore and not detect in those situations. This is why the system did not work during our sand driving even though the tire pressure was quite low. TLDR: With the wheel speed based systems if you change something; tires, inflation, wheels, balance, basically anything tire/wheel related, you have to hit a reset button. Quote Link to comment Share on other sites More sharing options...
Trouble Maker Posted July 28, 2020 Report Share Posted July 28, 2020 https://erwinsalarda.com/bmw-m3-e46-e90-e92-e93-2001-2013-tpms-reset/#:~:text=2006%20TPMS%20Reset-,TPMS%20RESET,Yellow%20for%20a%20few%20seconds. But if the tire is actually leaking and going low, you just need to fix that. Quote Link to comment Share on other sites More sharing options...
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