Tire pressure monitor questions

cherox · **Joined:** Sat Oct 12, 2013 6:09 pm **Posts:** 55

Hey guys, as I continue searching for new rims to replace my 20" Jet wheels with something a little smaller, I've come to a realization that the tire pressure sensors are going to be a problem one way or another.. It really got me thinking about how the TPMS works..

I guess my most important question boils down to this:
How does the Jeep computer communicate with the sensors? If each individual sensor has its own radio frequency, how do you change the computer when you do a tire rotation? Or do you even need to?

Does the system automatically figure out which tire is where and then update the computer to appropriately reflect that information?

Lastly, if I were to find other Jeep wheels (off another KK or even JK) equipped with their own sensors, what are the chances I could use them? Or is that a dealer scan tool job only?

Thanks LOST!

Cherrie 274 · **Posted:** Mon Jan 06, 2014 12:44 am

Mine is an 08 sport. I do not have a full size spare so only 4 TPMS's.
Mine only shows an icon in instrument cluster when a tire is low.
I have winter only tires mounted on Dodge Nitro rims without TPMS. The light goes on at about 15 miles after leaving my pole barn. My "summer" tires are about 10 feet from where my KK is parked. So it resets it's self. But
I have actually parked in a parking lot and had it reset by another vehicle.
My understanding is that there are a couple RF signals used. With mine they can "throw" the signal. So it doesn't matter where a tire is mounted. I have been told there is a kit to reinstall TPM, in the wheels. And that some wheels you can't use TPM because they won't seat properly. Dealer told me to expect batteries to last around 5 years. I'm over that. I just couldn't justify spending about 200 for TPMS in winter only wheels. Then to have summer wheels on and have TPMS die in one of them and spend more money.

Scar0 · **Posted:** Mon Jan 06, 2014 7:10 am

There are 3 transponders in the wheel wells. RF, LF, and LR
When the WCM needs to know which sensor is located at a particular location on the vehicle, it directs the transponder at that location to send out a low frequency signal to excite the nearby sensor. The WCM then receives that excited signal and knows where that sensor is located. This auto-locating process only happens in the first 10 minutes of any WCM cycle while traveling at speeds above 20 mph (32 km/h). (The auto-locating process will start again only if the vehicle has been shut off for approximately 20 minutes or longer). Once the WCM has performed this to the three locations that have transponders, it uses the process-of-elimination theory to know where the fourth sensor ID signal is coming from.

A Dorman part # 974-001 is a direct fit ($23 each). No programming needed. Just install, drive for 10 minutes over 25 Mph in an area without other cars. The system will learn the new sensor ID and location. Sometimes they can be difficult, so just in case, write down the ID before it is installed. That way if you need a dealer to program it into the system, they don't have to break down the tire again to get the #.
You can also get Schrader TPMS OE Replacement Sensors 28308
If you get new ones make sure they are 315 Mhz, the 433 Mhz are for Euro rigs.

If you want OEM sensors with a rubber valve stem. Look up 56029479AB

Cherrie 274 · **Posted:** Mon Jan 06, 2014 11:28 am

Hey Hi ScarO , I need to know, how mine that are not by my wheel wells does mine reset. And the time I was parked by another vehicle? They are in Pole barn, leaning 2 together about 10 feet away( last year further). KK is parked passenger side is closest.

Scar0 · **Posted:** Tue Jan 07, 2014 5:22 am

After a start, the WCM will query for sensors. Any that are within range will answer.
As you drive away from them, the WCM will query again. If there is no answer, then you get the warning.
When I broke one of mine, the dealer had a heck of a time getting it to self program the new one. This was because of all the other Dodges in the shop and parking lot as they were driving out.
After 10 minutes of driving, the WCM stops the query. then waits a while before doing it again.
So, yes it is possible your rig is picking up the signals from the ones in the barn. And if you were parked for 20 minutes, it could also pick up others in the parking lot at start up.
The WCM can store up to 8 different sensor codes at a time. It will look for those first. If there is no answer, then it will accept any that are within range.

Cherrie 274 · **Posted:** Tue Jan 07, 2014 11:32 am

So it's not just transmitters and a receiver, like it seems.
Thank-you for explanation.

jjohnson1892 · **Posted:** Tue Jan 07, 2014 1:52 pm

cherox wrote:

Hey guys, as I continue searching for new rims to replace my 20" Jet wheels with something a little smaller, I've come to a realization that the tire pressure sensors are going to be a problem one way or another.. It really got me thinking about how the TPMS works..

I guess my most important question boils down to this:
How does the Jeep computer communicate with the sensors? If each individual sensor has its own radio frequency, how do you change the computer when you do a tire rotation? Or do you even need to?

Does the system automatically figure out which tire is where and then update the computer to appropriately reflect that information?

Lastly, if I were to find other Jeep wheels (off another KK or even JK) equipped with their own sensors, what are the chances I could use them? Or is that a dealer scan tool job only?

Thanks LOST!

If you buy aftermarket, take the wheels/tires to a shop and ask them to transfer the TPMS sensors. I was in the same boat (Jet wheels to aftermarket 16's) and had this done. Simple and easy.

As the other guys mentioned, those sensors will most likely work for you.

As a suggestion, though, look for 16" wheels. They're the most popular/common and they bring a lot more options than larger wheels. I love the Moab wheels (Jeep), and I think the TJ (?) version is the same bolt pattern is identical. In hind sight, I wish I got some of those of Craigslist and some Duratracs in 245/75.

cherox · **Joined:** Sat Oct 12, 2013 6:09 pm **Posts:** 55

jjohnson1892 wrote:

If you buy aftermarket, take the wheels/tires to a shop and ask them to transfer the TPMS sensors. I was in the same boat (Jet wheels to aftermarket 16's) and had this done. Simple and easy.

As the other guys mentioned, those sensors will most likely work for you.

As a suggestion, though, look for 16" wheels. They're the most popular/common and they bring a lot more options than larger wheels. I love the Moab wheels (Jeep), and I think the TJ (?) version is the same bolt pattern is identical. In hind sight, I wish I got some of those of Craigslist and some Duratracs in 245/75.

I would love to find some TJ Moabs. They are the correct bolt pattern and look great on KKs. Unfortunately every time I find a set, they are way overpriced. Like I could buy brand new wheels and tires for cheaper.

Thanks for the suggestion of just swapping the factory sensors. I had heard that they were easily breakable so I didn't even think that was an option. Did you keep your 20s or did you get rid of them?

jjohnson1892 · **Posted:** Thu Jan 09, 2014 12:10 pm

cherox wrote:

I would love to find some TJ Moabs. They are the correct bolt pattern and look great on KKs. Unfortunately every time I find a set, they are way overpriced. Like I could buy brand new wheels and tires for cheaper.

Thanks for the suggestion of just swapping the factory sensors. I had heard that they were easily breakable so I didn't even think that was an option. Did you keep your 20s or did you get rid of them?

Honestly, if you can find a set in decent to good condition for $150ish per wheel, I'd go for it. I spent like $90/wheel on Black Rock wheels and they're already beaten up a fair bit, and the black shows it pretty bad.

20s are currently in my shed. I'm between A) getting a larger AT tire on them and using them for DDing and switching on my 16s for bigger wheeling trips B) getting a big MT tire on them and powder coating them black or C) selling them.

Probably going for C at this point. Tire choices are slim to none in terms of what I would actually want, and the actual look of 20's on a "questionable" Jeep as some have put it just seems yippie.

At The Helm · **Posted:** Thu Jan 09, 2014 12:54 pm

jjohnson1892 wrote:

cherox wrote:

I would love to find some TJ Moabs. They are the correct bolt pattern and look great on KKs. Unfortunately every time I find a set, they are way overpriced. Like I could buy brand new wheels and tires for cheaper.

Thanks for the suggestion of just swapping the factory sensors. I had heard that they were easily breakable so I didn't even think that was an option. Did you keep your 20s or did you get rid of them?

Honestly, if you can find a set in decent to good condition for $150ish per wheel, I'd go for it. I spent like $90/wheel on Black Rock wheels and they're already beaten up a fair bit, and the black shows it pretty bad.

20s are currently in my shed. I'm between A) getting a larger AT tire on them and using them for DDing and switching on my 16s for bigger wheeling trips B) getting a big MT tire on them and powder coating them black or C) selling them.

Probably going for C at this point. Tire choices are slim to none in terms of what I would actually want, and the actual look of 20's on a "questionable" Jeep as some have put it just seems yippie.

I'm always surprised its so hard for you guys to find TJ moabs. Out west there a dime a dozen! Here's today's craigslist search:
http://reno.craigslist.org/pts/4264848299.html

jjohnson1892 · **Posted:** Thu Jan 09, 2014 1:23 pm

Atthehelm wrote:

I'm always surprised its so hard for you guys to find TJ moabs. Out west there a dime a dozen! Here's today's craigslist search:
http://reno.craigslist.org/pts/4264848299.html

Think if I send him gas money he'll deliver to the east coast? :ROTFL:

At The Helm · **Posted:** Thu Jan 09, 2014 2:04 pm

jjohnson1892 wrote:

Atthehelm wrote:

I'm always surprised its so hard for you guys to find TJ moabs. Out west there a dime a dozen! Here's today's craigslist search:
http://reno.craigslist.org/pts/4264848299.html

Think if I send him gas money he'll deliver to the east coast? :ROTFL:

Hey that whay the ad says!

LKWJeeper · **Posted:** Thu Jan 09, 2014 4:06 pm

darn! All I could find is some guy who wants $500.. I'll stick with the Cragars.

Sent from my SGH-T999 using Tapatalk

cherox · **Joined:** Sat Oct 12, 2013 6:09 pm **Posts:** 55

Atthehelm wrote:

I'm always surprised its so hard for you guys to find TJ moabs. Out west there a dime a dozen! Here's today's craigslist search:
http://reno.craigslist.org/pts/4264848299.html

http://boston.craigslist.org/gbs/pts/4229881605.html

This is what usually pops up around here. If the link goes down, its a set of 5 Moabs on half worn 33s listed for $1500 Firm. Meanwhile a set of JK Moabs is going for $700 with less than 500 miles on the 32" tires.

I really wish AEV hadn't discontinued making the TJ Pintlers.. Those would be my number one choice.

Tire pressure monitor questions

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