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When I picked up my car the pressure in all four tires was 46 psi so I adjusted them to the proper pressure. Today I learned that I should have also initialized the tire pressure warning system (TPWS). The system operates based on the pressure level at which it was initialized. Since it apparently was initialized at 46 psi, it will not function properly until I initiallize it at the lower pressure.
That must be something standard Toyota does at the factory because mine were all at 46 psi too. I was surprised it wasn't adjusted at the dealership, though I did take delivery pretty much from the truck that delivered it to the dealership. Only way to get one around here is to search the dealers every day to see what is available and then beat everyone else to showroom.
 

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When I picked up my car the pressure in all four tires was 46 psi so I adjusted them to the proper pressure. Today I learned that I should have also initialized the tire pressure warning system (TPWS). The system operates based on the pressure level at which it was initialized. Since it apparently was initialized at 46 psi, it will not function properly until I initiallize it at the lower pressure.
Please do share, I also bumped mine down to 36 from 46 a few weeks after delivery. I rotated my tires recently and no issue with recognition in new position.
 

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2021 Sienna XLE
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285 Posts
Did you reinitialize the TPWS?
I believe it figures it out automatically. I brought the car in for the 5000 mile service and they rotated the tires. When I looked at the tire pressures (they were slightly different so I could tell), they had not changed position. However, shortly after I drove off, the tire pressures on the display changed to match the new positions. I could notice this because the dealer apparently did not check or adjust the tire pressures.
 

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Do you need to do something or reset something after a significant change in tire pressure? I would hate for a tire to go low and a light not come on because I decreased the pressures to recommended.
 

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2018 XLE AWD
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392 Posts
I am new to TPMS, but I understand that there are two basic systems. One will show pressure for each tire, the other is based on wheel speeds reported by the ABS rotation sensors.

One, or both, systems, will alert to a low tire if the pressure drops below the setpoint. Pressing the RESET button basically tells the system "Here is my set point, let me know when the pressure drops more than 5 psi."

If your system had been reset (at the factory?) to 46 and you dropped them to 36, they should have alerted immediately. Since they didn't alert, it's possible that the system was never told what the setpoint was.

This is all speculation on my part, and it is worth exactly what you paid for it.

.
 

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I just watched the car care guy video on tire pressure monitor system with most dedicated to the pre 2018 ones, but toward the end he said about reintialization, so that was as clear as mud to me if I need to do something. Maybe they were pre programed for 35 and they filled them to 46 for delivery. Who knows.
 

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2021 Sienna XLE Plus
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Maybe they were pre programed for 35 and they filled them to 46 for delivery. Who knows.
That's probably accurate.

My guess is the distributor fills them to 46 at port not knowing how long they'll sit before selling. Dealer should adjust at delivery but we know they probably won't.

Mike were filled to like 31, 34, and 35(2) at delivery.
 

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I guess I could take one down to 25, since I have a compressor, and see if a light comes on but again, that would be a PIA and it might not work until the car is in motion.
 

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2021 XLE Plus Gray
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I guess I could take one down to 25, since I have a compressor, and see if a light comes on but again, that would be a PIA and it might not work until the car is in motion.
REINITIALLIZING THE TPMS WHEN CHANGING TIRE PRESSURE
Look at page 430 of your Owner's Manual. It says:
"When the tire pressure warning system is initialized, the current tire inflation pressure is set as the benchmark pressure."
It also gives you detailed instructions for reinitializing.
 

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ACCESS TO JUMP START YOUR CAR
Storing your portable jump starter in an inaccessible place like the back battery compartment is not a good idea. If the battery is dead you can unlock the driver's door with the mechanical key and then unlock the hood to access the jump start connection. However, the only way to unlock the rear hatch is to tear it apart from the inside as described on pages 152-153 of the Owner's Manual. That is is why Toyota provides a mechanical key, a mechanical hood release and the jump start connection under the hood. Best to keep your jump starter somewhere that you can easily get to it with a dead battery. For me, that is the well in the console.
 

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REINITIALLIZING THE TPMS WHEN CHANGING TIRE PRESSURE
Look at page 430 of your Owner's Manual. It says:
"When the tire pressure warning system is initialized, the current tire inflation pressure is set as the benchmark pressure."
It also gives you detailed instructions for reinitializing.
Yep looks like a tomorrow project. What a pain, can't go in reverse to get out of my garage, have to drive it for 20 minutes, etc etc etc. Another demerit for my dealer......however I just rotated them so I should do it and for the tire pressure change I did 2 months ago.
 

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ACCESS TO JUMP START YOUR CAR
Storing your portable jump starter in an inaccessible place like the back battery compartment is not a good idea. If the battery is dead you can unlock the driver's door with the mechanical key and then unlock the hood to access the jump start connection. However, the only way to unlock the rear hatch is to tear it apart from the inside as described on pages 152-153 of the Owner's Manual. That is is why Toyota provides a mechanical key, a mechanical hood release and the jump start connection under the hood. Best to keep your jump starter somewhere that you can easily get to it with a dead battery. For me, that is the well in the console.
Most jump starters are lithium ion. Way to dangerous to be inside a Sienna.
 

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REINITIALLIZING THE TPMS WHEN CHANGING TIRE PRESSURE
Look at page 430 of your Owner's Manual. It says:
"When the tire pressure warning system is initialized, the current tire inflation pressure is set as the benchmark pressure."
It also gives you detailed instructions for reinitializing.
Finally found the right menus to re-intialize. Hit a long ok. Light blinked and went out. Drove (probably not long enough), got home. Went to tire pressure monitor menu......goose eggs. I will either have to drive more and hope backing up does not screw up the process or start again.
 

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Couldn’t one just crawl into the battery area in the back from the front upon unlocking the driver door manually with the physical key?
First time my Subaru Outback battery stranded me, I had my jumper cables stored in the rear under the cargo floor cover (which lifts up to reveal the spare tire bay). When the battery died, the rear hatch wouldn’t open, so I had to crawl into the rear from the front seat, lift up the cargo cover in the reverse direction, remove it completely (because when it is up, it blocks access between the rear seat and rear cargo area. Then I was able to reach my jumper cables. From that day on I kept a battery jump pack in the passenger seat back pouch.

The fact that you can’t open the rear hatch with a manual latching mechanism is a sign that modern cars are over-engineered, IMO.
 
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