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Old 03-19-2014, 06:46 PM   #1
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TPMS - Those Little Things That...

...the government requires, because half the world don't have the sense to know when their tire is low. Yeah! Those things. The very same that causes the dash light to come on and stay on until the tire pressure is brought to specs. Except in my case, my tire pressure is fine and above the minimum standard that I set with my SC 3865. Yet, that pesky little dash light stays on! Even bothered the local tire company to test each TPMS. They showed they were good and each battery was good. We even reset the SC to stock and lower each tire to 35#. No go. Still have the idiot light on! The only thing I have left, is to replace each sensor that currently have 51,000 miles on em. It's a gamble unless someone here can give me another idea to try. BTW - I reset my tune and checked for DTCs after being told that the TPMS was a separate setup from tuning or having anything to do with the DTC. Thought it was worth a try.

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Old 03-19-2014, 07:31 PM   #2
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The tpms system is all on its own you will need a good scanner to access it at all. If the sensors tested fine I would sug having a shop scan the tpms module for codes it will tell them what is not reading correctly. Its possible that the sc sent a bad code into the module and now it needs a reflash to work properly again.

if you take to a shop in this case I would sug a dealer simply because they will have the scanner needed for sure that can access it and tell you whats wrong. throwing sensors at it will still require a scanner to enter new transponder codes.

this is one of those cases where I sometimes send the cars to dealers to correct the tpms light issues. you could also try a batt disconnect for a shot in the dark at it working.
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Old 03-20-2014, 01:18 PM   #3
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Did the battery disconnect for ten minutes this morning per suggestion. Thanks for that c392. Unfortunately, it still lights the light. Going to the dealer to let them handle it from here. It's all good...Thanks again c392!
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Old 03-20-2014, 03:58 PM   #4
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I have had a tpms not reset due to the tyre depths, 1 tyre being a lower tread depth than the rest. Just a thought.
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Old 03-20-2014, 04:56 PM   #5
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They use the ABS to read tire diameter? My Chrysler and Mazda actually have a sensor in each wheel.
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Old 03-20-2014, 08:35 PM   #6
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Have you checked your spare, depending on year of vehicle, some had sensors in the spare as well.

Quote:
Originally Posted by MikeHTally View Post
They use the ABS to read tire diameter?
The first gen tpms used ABS speed sensors to calculate tire revolutions not diameter. A tire with less tread spins more than a tire with more tread, ABS ecu looks at wheel speed per axle, if they differed, it would trigger light. You could only have a tread depth difference of 3/32 per tire on that axle.
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Old 03-21-2014, 06:06 AM   #7
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Quote:
Originally Posted by HemiSuperBee View Post
Have you checked your spare, depending on year of vehicle, some had sensors in the spare as well.



The first gen tpms used ABS speed sensors to calculate tire revolutions not diameter. A tire with less tread spins more than a tire with more tread, ABS ecu looks at wheel speed per axle, if they differed, it would trigger light. You could only have a tread depth difference of 3/32 per tire on that axle.
Right, which means there would be no sensor inside the wheel.
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Old 03-22-2014, 12:32 PM   #8
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Not sure about a sensor for tire diameter. New one on me. I know for sure that each tire has a sensor when I bought new tires for my truck. Since mine is an 08, I guessing the sensor reads just pressure and nothing more.

Just the same, Want to hear a funny story? Yesterday, I had an appointment with a local dealer/service department, in whom I trust, in the metro Phoenix area. On my way to keep said appointment, my little dash indicator light turned off and stayed off. Wouldn't you know! Now, I have heard and read dozen of stories about modules, wiring, chips and gizmos on new and newer rides. Even a few stories that simulate exactly what happen to me. So, I knew the answer before I even placed one tire on their service bay. Once I was there, the old adage, "If it ain't broke, then don't fix it" came into play. Of course, that was followed up with a very kind reply, "If it happens again..." Meh! Oh well! I thought I had something to complain about. I didn't argue the point. There simply wasn't anything to inspect or repair with the tire sensors. It all ended well. While the truck was there, I had the front end components inspected and a maintenance inspection. It was a 'little dusty' from our last haul to and from CO, so they ran it through the wash. Then they let me go without paying a dime. Gotta love it!!!

Yeah, all is good. My thanks to all who replied and I'll be sure to check back in to HT when Ram/HEMI issues happen again. Much appreciated!
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Old 03-22-2014, 02:51 PM   #9
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There is no "sensor" for tire diameter. Some systems use the ABS to "guess" a tire is low by comparing wheel speeds. An under-inflated tire is smaller than a properly-inflated one, so it turns faster.

My 300 and Mazda have sensors in each wheel - the Mazda tells me A tire is low, the Chrysler tells me which one.
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Old 03-24-2014, 07:29 PM   #10
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By 2008 60%of all passenger vehicles had to have sensors by 2010 100% had to have sensors the sensors measure psi and temp inside the tire some scanners show the temp some don't.At work I deal with sensor issues all the time. get this anytime you change a tire (after its tread is gone) a new sensor is strongly suggested but nobody ever does them at 65-120$ each nobody wants another 400$ ontop of there already 600-1600$ bill.

Chevy uses abs sensors to sense tire diameter in the mid 90's-2000's only down side if they all leak down the same you could end up driving on 4 low tires one had o be at least 5% diff to trigger the light. needless to say all this electronic stuff is getting crazy. just wait 13/14 Chryslers/dodge have a 1/4 the fuses as before and use high/low side drivers fuses are gone and fiberoptic cables for lightspeed data acquisition starting as early as 2015/16. cant wait for that when a customer comes in and says I cut this wire to run stereo now truck wont start. this is why I am constantly going to training classes and buying new specialty tools all the time.
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