I really like the tire pressure monitoring system in the SF. Kinda confused on one aspect. Apparently, it can identify which tire is low on pressure and indicate this wheel position on the dashboard. How does the system know which tire the signal is coming from? Lets assume for a minute each sensor transmits a unique frequency. What happens when you rotate tires? Do you have to re-assign each sensor in the system so it knows what tire is whereon the vehicle?

Craig
'07 Santa Fe

I have nothing to base this on, but I would guess that it would have to do with the car being out of level toward a certain direction. That would seem the simplest way to do it.

The TPMS uses a special valve stem assembly for monitoring. I know that because the owners manual says not to use any "fix-a-flat" type tire sealer to repair a tire because it will ruin the sensor in the valve stem assembly. I don't know about rotating tires and how it "knows" which tire is where though - good question.

The system works like this:

Each corner of the car has an LFI (low frequency initiator) that sends a signal to the TPMS wheel sensor to "wake it up".

You have a left-front, right-front, left-rear and right-rear initiator.

The initiator is what helps determine the wheel position, not the wheel sensor.

When you start up the car, the TPMS receiver sends a signal to the initiator which then sends a 125mhz signal to the sensor in the tire. That wakes up the sensor, making it send a 315Mhz (or thereabouts) signal to the receiver. The tire sensor periodically monitors pressure, temperature and rotation.

How does the receiver know which tire has which sensor? Simple. When the TPMS receiver sends the signal to the LFIs, it does so in a predetermined sequence. So when the LFI wakes up a wheel sensor, the receiver knows that that sensor's ID matches the location of that particular LFI.

The receiver keeps sending a signal to the LFIs about every 10 minutes or so to keep the wheel sensors awake while the key is in the ignition.

This post has been edited by R4M0N: Jan 24 2007, 04:11 PM

R4MON,

First let me say you sound like you know what you are talking about. Are you an engineer? Can I assume each sensor is near each wheel?

Craig
'07 Santa Fe

I'm a computer guy, not an engineer. But I did stay in a Holiday Inn Express last night. :grin: I basically paraphrased what I've managed to gather since I bought the Santa Fe in December. The wife drives it and I figure out how it works and how to fix it. :thumbsup:

Each LFI is in the wheel well at every corner of the car.

If you guys really want to dive into how the car works, go to
http://www.hmatraining.com/
And
http://www.hmaservice.com/

Thanks r4mon, that was a nice description.

I put on winter tires, and got a set of four oem valve stem sensors for the tires so that we could still have the TPMS functionality. The system did not recognize them after we put them on, even after a few hundred miles. The wife took it into the dealer, and they reset the system, and now they work, bt I don't know what they did to reset it but I need to know so I can do it again if necessary when I switch back to summer rubber. All tire type folks I talked to said that they thought the system should auto-recognize the sonsors after a while, but that obviously wasn't happening.

You have to have the hyundai diognostic programer to enable the monitor of the system to recognize a new sensor.i just read this under< suspension system/TPMS/troubleshooting> in the shop manual.

Well guess that means I'm making a trip to the dealer twice a year every time I switch over the tires.

But what part exactly are you referring to in <suspension system/TPMS/troubleshooting>? I took a look at it, but it doesn't seem to specifically mention new sensors. Was it mentioned in one of the DTCs? Thanks.

it was in the regular shop manual, under suspension,and then tpms .I kinda stumbled upon it myself.
I put some winter tires on and opted not to get the monitors.I'm just hoping when i put the reg wheels back on, that the monitors 'wakeup" o.k.