Subaru TPMS: WTF, yo?

Just wondering whether anybody understands this system and the dance surrounding swapping out tires.

I have a tire shop which I consider to be not staffed with idiots. They've been doing a serviceable job of pretty much everything I need for years. Maybe not exceptional, but not exceptionally bad by any means.

BUT.

Every time (5 instances at this point, IIRC) I go get the winter/summer tires swapped on a Subie (2012 WRX, 2009 Legacy), they do the physical swap, then later that day or the next day the TPMS light comes on, and I have to go back and have them re-explain the new sensors to the car.

I've preemptively reminded them of the issues from the previous trip. I've kept my mouth shut. I've asked for an explanation, and if they gave me one, it didn't really stick. I recall something about the idea of issues caused by having the not-in-use tires in the trunk/hatch/back seat after doing the swap, which makes no sense to me. If it was learning or sticking by being able to talk to those tires, you'd think it would be one of the systems which doesn't need to be explicitly programmed. If it needs to be explicitly programmed (which is my understanding), you'd think it would talk to the right sensors and ignore the disused ones.

So, like I said; WTF?

If it's an "auto-learning" system then yes, taking back the other set in the trunk could be causing the problem. You'd need to have someone else carry them back, or wrap them all in tinfoil

In reply to GameboyRMH:

That's the thing: The Subaru setup is not auto-learning. As little as I've been able to pin down about it, one thing is that you do need to read the sensor IDs off the tires you want to use, and specifically enter them into the car's computer. To my chagrin, this is utterly separate from OBDII stuff. The tools are getting cheaper, and if TPMS sticks around, I may splurge. Better still, they're starting to do "cloneable" sensors, so you get blank ones, and have them set to the same IDs as your other tires so the computer can just keep looking for the same IDs.

But I digress... What the heck is happening now? It's almost like the Subaru computer won't take the new IDs 'til after it throws the light or something. Not that I think that's actually what's happening, but I just can't imagine how a shop in Portland, which must swap out dozens or hundreds of late model Subaru winter/summer tires a season, could need two swings at it every time.

The Subaru TPMS only allows for one set of sensors per car, so if you have multiple sets of wheels/sensors, you have to reprogram them every time you swap the wheels. It's stupid.

SilverFleet wrote: The Subaru TPMS only allows for one set of sensors per car, so if you have multiple sets of wheels/sensors, you have to reprogram them every time you swap the wheels. It's stupid.

I agree it's stupid, but the question I have is why reprogramming them seems to fail the first time, every time.

I go in, I get the tires swapped, I theoretically have the new sensors programmed in, then the next day (or later same day) the light comes on and I go back and have them programmed again.

Five occasions, two cars.

The common threads are the shop and the Subaruness, but as I outlined above, the shop doesn't strike me as so bad that they would routinely make this mistake for every Subaru that passes through every change of seasons. Moreover, my impression is that it's several Asian brands, not just Subaru, which do the non-auto-learning TPMS.

In reply to Streetwiseguy:

Reasonable, but I just can't do it. Newish car (bizarrely newish car for me), and money out of pocket for sensors. I will not bodge things. Moreover, the tires are now on girlfriend's mom's car, and I don't want to train her to ignore anything. I want her to believe any light on the dash means Stop Driving Until You Get Answers.

When you program the new sensors, the old ones shouldnt be anywhere near the car.
If they put them in the trunk then reprogram, the computer is picking up the signals from some of the old ones as well so when you remove them and deive with only the new ones, it isnt familiar with their ids.
Have them program the new ones with the old ones on the other side of the shop or something and it should work.

They probably don't reprogram them. with my wifes saab when i change to winter tires that do not have the TPMS sensors it takes about 15 miles for the light to go on. I bet they check the car the light goes off, then you drive home and the light goes on, and you have to take it back.

If one set of sensors is clones of the other, and they probably are, then when you drive away the car is finding two sensors with the same ID and throwing a code for that.

If one set of sensors is clones of the other, and they probably are, then you don't need to go somewhere for reprogramming because to the car one set of tpms sensors looks identical to the other. Change them at home and you may not even need to go in at all.

In reply to oldopelguy:

They came from the same shop that's doing the swap each time. If they were cloned and having that issue, then I'd expect it to sort itself out pretty quickly after getting the extra tires out of the car.

Why do you suggest they're probably clones? They're a couple of years old, and while I'm certainly not up to speed, I'd never heard of cloned sensors 'til a couple of months ago.

So far the fix has been to return to the shop and have them re-reprogram the sensors. You'd think if they'd sold me cloned ones, they'd just tell me to keep driving after putting the extras in the basement rather than having me come back to the shop. They're not getting paid extra (they do all the swaps for "free" post tire purchase), and it's using up everybody's time...

Thanks for all the replies.

It seems to me that neither Subaru nor the shop should be let off the hook with regard to being complete, berkeleying imbeciles.

The upshot seems to be that Subaru chose an idiotic system requiring explicit reprogramming, yet which somehow "clings" to the old sensors if anywhere near the car, thereby having the worst parts of both self-learning and explicitly-programmed systems.

It also seems to be that despite Portland being the Subaru capitol of my known world, this shop consistently fails to do the swap in a way that doesn't result in the customer making two trips, and the shop having to clear out a bay, pull the car in, re-reprogram it, and just generally waste everybody's time.

In future, I will indeed be figuring out who can set me up with cloned sensors so I can do this in my driveway and have done with it in 20 minutes on my schedule instead of two stretched lunch hours.

I put a tiny square of matte black trim tape over the light, and have never taken it off. TPMS is on my winter tires/stock wheels, but if one goes flat, I don't need a damn light to tell me so.

Did the same thing on wife's Sequoia, rather than get 2 of them fixed.....

TPMS = delete it, problem solved.