I see a lot of random stuff about this online and was trying to find a definitive answer.

I have the fancy EVIC that shows tire pressures. Two questions:

1. If I rotate the tires, how does the TPMS system know where the tires are on the display? Do I need to do anything? I've read it supposedly learn's itself but not sure how this is possible without some fancy signal reading sensors.

2. I randomly will get a TPMS error. All 4 sensors are new except spare maybe. I suspect spare sensor is either low battery or low pressure sometimes. But it won't say check spare or spare is low. It just gives a general error. Is this normal operation? I think it's buggy and doesn't have a specific message for the spare, and just throws an error

Thx!

Wow, didn't know that was an option in 2005. Mine doesn't have any TPMS (thank god)

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2005 CRD "Ol' Blue"
Red Ryder carbine-action, two hundred shot range model air rifle with a compass in the stock and this thing which tells time.
My build page- RL Komodo Rear and TJM Front Bumper, armored, lifted, JBA Steel D30, 4.10s and ARB air lockers.

It’s nice to see the pressure levels on the EVIC i actually like that but they can be a pain. With the proper computer tool it can be coded out altogether though I saw a post about that.

I have the same system, the TPMS self calibrated to the new locations for the tires when you rotate them.
There at 3 "receivers"...2 for the front tires at about the 11'oclock position under the bumper cover and fender liner and 1 in the right wheel well near where the rear bumper bolts up (you can actually reach up and unplug it).
The transmitters that are inside the tire valve stem "wake up" once it senses rotation and transmit at 33mhz that is picked up by the receivers and sends the pressures to the TPMS module located in the steering column to be displayed on the EVIC. No learning or program is needed

There is a pretty good explanation of the both types of TPMS in the service manual.

If you had a sensor in the spare (not all jeeps had them) you would get check spare or spare low message with a blinking tire light on the cluster.
If you had a main tire that was low you would get a check TPM message and a solid tire light on the cluster. On the pressure screen, the low tire would be blinking.
If you had a bad sensor, you would get the same as above, except for the tire with the bad sensor would indicate dashes. Note: sometimes the receiver can't pick up the sensor which may indicate a bad battery.

I put a sensor in my spare so I could do a 5 tire rotation. Sometimes I wish I didn't put the sensors in my tires as when I air down for the trails I would stop looking at the blinking light . I would have just made a PVC canister with a tire valve so I could pressurized the canister and store it under the seat.

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05 CRD; Rebuilt top end w/ARP studs, EGR delete, SEGR, 3.7L HD cooling fan, Samco hoses, in tank pump, JBA coil overs & control arms, KK clevis fork, 1/2" cradle drop, 1/4" motor mount lift, WJ rear upper trilink w/WW mount, WJ lower control arms, 4:10 gear, front/rear air lockers, ARB bumper, Rock Lizard sliders/roof rack, Mod T-stat

I wonder how it can self calibrate. Using only signal strength isn't that easy. Yea I've seen my rear right one! Ok that's good to confirm it somehow works lol.

I don't ever get the spare low message but it seems it's related. I haven't done formal testing. I put more air in spare and the genetic check TPMS message goes away lol. No blinking tire light just says check TPMS randomly and it's solid on the EVIC, no light on dash. When I get these errors all 4 tires are OK. It's almost as if spare is giving it data but it doesn't know how to process it, giving weird errors. I never did the spare tire sensor so maybe it's battery is low, another option. It never says check spare or shows anything about a spare though!

I could remove sensor from spare and it would all go away?

I don't know...it might.

I know when I had no sensor in my spare, and I aired back up after a day on the trail, I kept getting the spare low light and the flashing tire light in the cluster every 10 mins (ie, flash 4 times, turn off for 10 mins, flash 4 times...rinse and repeat) at least from what I can remember. This went on for about 2 months till one day it stopped. have a feeling it was tied to complete drive cycles but the service manual did not go into detail about it.

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05 CRD; Rebuilt top end w/ARP studs, EGR delete, SEGR, 3.7L HD cooling fan, Samco hoses, in tank pump, JBA coil overs & control arms, KK clevis fork, 1/2" cradle drop, 1/4" motor mount lift, WJ rear upper trilink w/WW mount, WJ lower control arms, 4:10 gear, front/rear air lockers, ARB bumper, Rock Lizard sliders/roof rack, Mod T-stat