official TPMS info from Toyota tech training class

edit: briefly updated to correct the post, more info to follow.
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short answer: the 06 has direct TPMS only.

long answer: so the training manual we referenced when originally writing this post did not have a description of the new direct TPMS, and instead was describing the old system. based on the info we had, if a car had the reset switch along with the direct sensors, it had to have both systems.

the old system had a stored "ideal tire pressure" value pre-programmed into the TPMS ECU that differed for each model, and could not be set to user-specified values. this is why there was no reset button on the old direct-sensor systems, and why we concluded that there were 2 systems.

the new system, which is on the 06 prius, allows for user-defined tire pressures, which for us and our slightly more inflated tires for better mileage, is great. hence the reset button for the direct sensors. you can set your own tire pressure and instead of waiting for the pressure to drop 25% below the specified pressure (which would have been whatever is in the door sill, i think it's 35/33) rather than getting a warning light when the pressure dropped to 25% below your preferred 42/40.

still the same principle aside from that. sensors integrated with the valvestem that measure pressure in your tires and transmit the info to a TPMS antenna, which is wired into the TPMS ECU. it sends a warning light on the dash when you lost 25% of your tire pressure.

sensors are run on Li-ion battery that lasts about 10 years and are in sleep mode until they are installed to prevent battery rundown while sitting in your local parts department.

there is no "main/2nd" switch in the 06 prius, as i've been told. this isn't surprising, i think there's only one or maybe 2 models out there that do have the switch. this means getting a second set of wheels with snow tires or the like on them is going to be a real pain in the butt and quite expensive. you'll have to have the TPMS ECU reprogrammed at the dealer twice a year, it requires the scantool. plus you'll have to have the 7-digit code written down for each of the sensors, including the ones that are installed in the OEM wheels, which means breaking the seal on the OEM tires and reinstalling the tires. it's going to be cheaper to have new tires mounted at the change of seasons rather than having a spare set of wheels.

DocVijay asked the question below about using a different angle sensor for non-OEM wheels. theoretically it could work, but he's going to bravely be the guinea pig here and see what the results are. all in the name of discovery! let's give the guy a pat on the back.

i have yet to see the reset/re-initialize info, will post that too as soon as i get my hands on it, which will be later on tonight.

i am glad DH is the tech and i'm not, having to learn about all these new things being sent out all the time on new cars would be a real pain!

 

-_- you're very welcome. i do what i can to contribute.

and i have been deemed "cool" too... what a great day B)

 

one more thing. the valvestem sensors are run on batteries, which last around 10 years. expect to replace them every 10 years or thereabouts.

 

yep. i put that in this section:

increasing pressure in all 4 tires would include the situation of increasing the pressures to 42/40.

 

suppose that'll further reduce the chances of ever making your money back on a prius, huh? :lol:

actually, you have to replace the whole sensor when the battery dies. and i have more info to post here once the cat gets off my chest... which may be a while.

 

stumbled upon something interesting in the book. i'm going to ask DH to clarify this whole thing for me before i post any more. i think he'll have to do some digging around in the system at work, which won't happen until tuesday. sorry to shake things up, guys.

 

okay, info triple checked and verified from the repair manual. still not complete but i'll get to that tonight. (i hope!)

 

i guess the question is whether the old system sensors are going to work with the new system. we have no reason to believe one way or the other- the changes appear to be based in the ECU and how it's reset, but it is possible they changed the radio frequency of the transmitter and receiver. i don't know if they would change that or not. he said the caps that he's seen on the prius are black, but the old sensors are chromed, so it may be a new part altogether which would be a problem.

the vehicles we know of that have the direct sensors are the tundra, land cruiser and one other truck/suv type. i can't ask him at the moment. all the cars until 06 have had indirect TPMS.

because this is a new system he's not sure which vehicles have it vs. the old system. they've introduced a lot of big changes in their TPMS recently, hence all the confusion on our end. i think you're also going to run into more issues at the parts counter if this requires a newly created part, because it might not be available for a while.


couple relevant points from the repair manual:
under the following conditions the system may not function properly.
-if wheels other than the specified ones are used, the system may not function because different radio waves are transmitted from the tire pressure warning valve and transmitter.
-depending on the tire type, the tire pressure warning valve and transmitter may not function properly even though the specified wheels are used

the first one makes me wonder if that was lost in translation. the wheel won't change the radio signal emitted from the sensor, would it? maybe they meant to say sensor?

 

will have to dig into the procedure for replacing the sensors. the overview DH brought home for me doesn't give a definite answer, Jim. but that is a very good point, now that they've gone and redone things.

all i found was this:
"if the transmitter ID has already been registered, the ECU compares the measured air pressure value with the standard value."

looking at the reset procedure, they don't mention if that would maybe register the transmitters.

will try to get info over the next couple days.