Hey everyone,
I just purchased my Sienna a couple of days ago & received the all weather mats from Toyota at the time of purchase. The dealership attempted to install them but ultimately said I'd probably have to trim them myself to get them to fit.
I found this forum after standing in my garage & scratching my head trying to figure out how to put the puzzle together. Unfortunately, it seems like everyone is having the same issue or trying to find an aftermarket solution.
I was able to install the Toyota all weather mats myself & thought it would be helpful to post how to do it.
There are going to be a lot of mats involved but 4 of them are narrower than the remaining 2 mats. The 2 mats that are wider will be used for the aisle. The other 4 go under the second row seats & reach back to the 3rd row. It was easiest to use the 2 short & narrow mats in front of the 2nd row seat & use the longer section to go under the 2nd row seat & back to the 3rd row. There isn't enough clearance for a mat to go under the section that slides out with the cup holders for the 2nd row.
First, remove the factory installed carpet mats between the rails & in the aisle. When you remove the carpet mats you'll see there are tabs under the rail holding them in place.
View attachment 2217
View attachment 2216
You'll want to use a flathead screwdriver or a similar tool to help push the edge of the all weather mat under the rail. There are 3 edges or lips on the all weather mats that can be used the same way to achieve a snug fit. When I installed them it worked best to just get the first edge hooked on one side then make sure the mat is still aligned where you want it b/c it will probably move depending on the force required to get the mat under the rail. I was only able to hook the first edge for under the seats & in the aisle I was able to get to the second edge easily.
View attachment 2218
View attachment 2219
View attachment 2220
Once you are finished it looks pretty good & it's snug. My only concern is dirt getting into the rails & causing them to have difficulty sliding in the future. It should also be worth noting that there isn't an all weather mat to replace the factory carpet mat between the sliding doors & 2nd row seats.
View attachment 2221
View attachment 2222
View attachment 2223
I hope this helps! I've used google & forums to solve lots of problems I've run into & I finally get to repay the favor.

Jeff