At what psi does the tire pressure monitor come on when the tire pressure is low? in other words, what psi does our prius consider "low" to notify us and turn on the TPMS?
you set it by setting tyres pressure first, then resetting the button. i think it comes on one psi below that. so if yours is still factory, one psi what is on the door jamb. although some have reported it has to go substantially below to set off the warning.
IIRC The TPMS will alert you at 20% below the set pressure. It should already be set as the computer remembers the last time it was set. If you suspect it isn't, or if you want to change the setting, you can use the reset button to set new values. Fill the tires to the desired pressure first then reset. On mine, the button is below the steering wheel, by your knees, at the centerline of the steering column. I dont know if it's the same on all versions. I've only done it once and i found the instructions here on the forum. I don't remember the details well enough to quote them now.
See the post in the GIII part of the forum. It's about 20% below the set value, and the set switch is on the bottom of the dash by the steering column. The set value is for each sensor, so different pressures can be used with different alarm points.
According to my manual, you "initialize" it through the Settings part of the multi-information display. You switch to the gear icon, select "Vehicle Settings", and scroll to "TPMS" (after you've set the tires to the pressure you want and then turning the car on). I don't think my 2016 has a TPMS reset button on the dash.
Gen 4 same as Gen 3, TPMS triggers at 20% below the set psi, which can be initialized on the menus after you have pumped up your tyres to your required pressure. A trick to make it more accurate than 20% below, or to set the threshold higher, is to over inflate your tyres then initialize it. To make it trigger as soon as the pressure drops below the required tyre pressure, you could over inflate by 25%, initialize it, then deflate the tyres to the required pressure. To make it a less sensitive, use less over inflation before initialization. Examples: Highest sensitivity: if you normally run at 40 psi, fill the tyres to 50 psi, initialize the TPMS then drop the tyre pressures back to 40 psi. 10% drop triggered sensitivity: normal 40 psi, inflate to 45 psi, initialize then drop to 40 psi. All pressures set and checked cold of course.
I would guess they'd set tires to spec pressure, do the TPMS set procedure, then raise tire pressures to max sidewalk for shipping.
My car was delivered with tire pressures 2-3 psi below the placard. The first weekend I inflated the tires to the proper pressure by the gauge I use and reset the TPMS. I then check them monthly.
So does the TPMS send a signal wirelessly to the ECU???? This is really over the top stuff. I had 3 tires punctured by a vandal on my '16 4 Touring. Apparently when the dealer to whom the car was flat-bedded replaced the tires they damaged the senors. They "did not have the tool" to reset the computer -- told me to take it to a biger dealer. Bigger dealer says smaller dealer damaged the sensors. Being replced under warranty. Good thing -- they are $178 each.
I don't know about the Prius, but when I had my tires replaced on my '08 Chrysler Pacifica, Tires Plus recommended replacing all four TPMS sensors with new ones. They charged me roughly 10 bucks apiece. I would assume TPMS sensors are common among all vehicle manufactures. Unless there is something special about Prius TPMS sensors, it sounds like they were quoting you a bill of goods.
That's a really cheap price the Toyota OEM units cost $30-40 each on Amazon, not including installation Often when they change tires they like to replace some of the washers and things ("TPMS maintenance kit") but not the whole TPMS. But replacement at tire change can be a good idea. Mine have lasted 9.5-years one died the rest still working 10+ years.
I thought the TPMS sensor was just some generic part that used a common telemetry standard across manufactures to keep the cost low. This was my first run-in with having to replace them so my knowledge is limited and my naivety got the best of me. I probably would have passed on replacing them if they weren't so reasonably priced and installation included in the tire change.
Parts cost low? Toyota? Ha ha ha ha! Nice joke! The chip inside the sensor might be the same over some manufacturers, but even that I doubt. I wonder if you got the valve stem insert replaced instead of the actual sensor?
