How the heck does the TPMS work?
12-31-2008, 04:12 PM
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How the heck does the TPMS work?
I did a search here and went through my owner's manual, but didn't find the answer.
I just changed my oil and rotated my tires yesterday. Then today, my tire pressure monitor goes off, saying my front driver's side tire is low. I put air in it and all is well (warning went away). For the record, I did set all four tires to the right pressure while I was at it.
It then dawned on me that yesterday, that tire was on the rear passenger side. I assume the sensor in the tire wirelessly transmits info since I didn't have to disconnect any wires to rotate my tires. So, how the heck does the computer in the car know what wheel/tire is mounted where? Is there a separate receiver at each axle end or something?
Just curious here...
I just changed my oil and rotated my tires yesterday. Then today, my tire pressure monitor goes off, saying my front driver's side tire is low. I put air in it and all is well (warning went away). For the record, I did set all four tires to the right pressure while I was at it.
It then dawned on me that yesterday, that tire was on the rear passenger side. I assume the sensor in the tire wirelessly transmits info since I didn't have to disconnect any wires to rotate my tires. So, how the heck does the computer in the car know what wheel/tire is mounted where? Is there a separate receiver at each axle end or something?
Just curious here...
12-31-2008, 04:27 PM
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I don't have this system in my car (2005) but from what I have red, in some cars you need to reset the tpms when rotating the tires for the computer to realize the tires are on what wheel. Some cars, maybe not yours but some. I have also seen, you need to drive the car a few miles before you get an accurate reading from the sensors. My father in laws FX has stars in the display until the car is driven a certain distance.
12-31-2008, 05:40 PM
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01-01-2009, 01:04 AM
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Hmmmm, no better answer than "magic"?
Here's how I *think* it works (should be pretty close).
Each wheel has a TPMS sending unit. This unit contains some sort of pressure sensor and a radio sending unit.
The car has a reciever that takes the signals from the sending units and displays that information in the MID. I *think* the unit on the car side also determines whether the pressure is acceptable and if not sends an error message to the dash and/or MID.
Any sending unit can be placed in any position and the car determines which sending unit is at which wheel (i.e. you can rotate tires and the car measures/displays the pressure for the new postion automatically).
I am not sure how the car knows which signal comes from which sending unit - is there a receiver for each wheel position or is it really magic? (Parts drawing shows only 1 receiver, so that part is still magic to me - http://www.acuraautomotiveparts.org/...s=&view=normal ). Maybe something in the frequency or timing that is established during the recognition period - some kind of "handshake" between each sending unit and the reciever.
I do know when first start the car, if you click into the MID display real quick the readout will show 58 psi. Then it will adjust to the correct psi in a specific order (RF - RR - LR - LF).
The TPMS seems to be modestly accurate with the difference between what is displayed an what you'd directly measure with a decent guage between 0 and, say, 1 or 2 psi. A couple of mine seem to be off by ~.5 psi, the others are right on.
Here's how I *think* it works (should be pretty close).
Each wheel has a TPMS sending unit. This unit contains some sort of pressure sensor and a radio sending unit.
The car has a reciever that takes the signals from the sending units and displays that information in the MID. I *think* the unit on the car side also determines whether the pressure is acceptable and if not sends an error message to the dash and/or MID.
Any sending unit can be placed in any position and the car determines which sending unit is at which wheel (i.e. you can rotate tires and the car measures/displays the pressure for the new postion automatically).
I am not sure how the car knows which signal comes from which sending unit - is there a receiver for each wheel position or is it really magic? (Parts drawing shows only 1 receiver, so that part is still magic to me - http://www.acuraautomotiveparts.org/...s=&view=normal ). Maybe something in the frequency or timing that is established during the recognition period - some kind of "handshake" between each sending unit and the reciever.
I do know when first start the car, if you click into the MID display real quick the readout will show 58 psi. Then it will adjust to the correct psi in a specific order (RF - RR - LR - LF).
The TPMS seems to be modestly accurate with the difference between what is displayed an what you'd directly measure with a decent guage between 0 and, say, 1 or 2 psi. A couple of mine seem to be off by ~.5 psi, the others are right on.
01-01-2009, 01:14 AM
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09/03/2003
TIRE PRESSURE MONITORING SYSTEM
New for all 2004 MDX models is the application of a direct Tire Pressure Monitoring System (TPMS). Using a series of four sensors and four initiators (one for each tire) and a receiver to capture and relay information, the system alerts the driver when it detects that tire pressure in one or more tires drops significantly below the recommended pressure.
The sensor transmitter is located inside the wheel. Should the tires be rotated around the vehicle due to normal maintenance or be replaced entirely, the new tires are "auto-located" by the system. If the system detects that tire pressure is significantly low (32 psi is recommended), a low tire pressure indicator located in the meter containing the fuel level and temperature gauge will come on while a schematic of the vehicle located in the center meter housing the speedometer will indicate which tires are low.
TIRE PRESSURE MONITORING SYSTEM
New for all 2004 MDX models is the application of a direct Tire Pressure Monitoring System (TPMS). Using a series of four sensors and four initiators (one for each tire) and a receiver to capture and relay information, the system alerts the driver when it detects that tire pressure in one or more tires drops significantly below the recommended pressure.
The sensor transmitter is located inside the wheel. Should the tires be rotated around the vehicle due to normal maintenance or be replaced entirely, the new tires are "auto-located" by the system. If the system detects that tire pressure is significantly low (32 psi is recommended), a low tire pressure indicator located in the meter containing the fuel level and temperature gauge will come on while a schematic of the vehicle located in the center meter housing the speedometer will indicate which tires are low.
http://www.hondanews.com/search/rele...q=tpms&s=acura
^^ Thats the earliest and most complete description I could find in the Honda New Archive.
01-01-2009, 06:53 PM
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So it sounds like the transmitter in the unit that goes in the wheel is short range and the receiving sensor is pretty close to each wheel. Makes sense. Also makes it a heck of a lot easier to rotate your own tires.
Thanks Bearcat!
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