Fixing a Wonky Rear Window that Rolls Down by Itself
 

The Issue

Like many of us, the roll down rear cargo window is well appreciated feature of the 4Runner and one that I use often in the summer months. This made it all the more concerning when this spring I started having issues with the window. The first appearance of the issue was when I walked out to my vehicle one evening and noticed that the rear window was rolled down completely. I’m dumb enough to forget to roll it up when I park sometimes so I chalked it up to that, but then then next day it happened again and the window rolled itself down with the vehicle off. Over the ensuing weeks the issue got worse as when I used the console control to lower it the window would go up and down fairly erratically. It then evolved to a situation where as soon as I’d lock the doors upon leaving the vehicle the window would roll down (not always all the way, but part way). I should also note that the issue would appear for a day or two at a time, and then go away. However when it “went away” the rear window was inoperable, i.e. it couldn’t be rolled down or up.

The Fix

I’ve learned that T4R is the first place to check out in such a scenario. Similar (but no the exact) issues have been experienced by other T4R users, with most being fixed by either re-aligning the rear window wiper by pushing it all the way up into its seating, or replacing a fuse. None of these worked. Others around here were able to replace the rear window ECU to fix some rear window issues (not the exact same as mine though) but that was a spendy option with no assurance of resolution. The one thing that was mentioned by other T4R owners with rear windows issues was the role moisture seemed to play. This was interesting because in hindsight all of my window issues were after a decent rainfall where the vehicle was outside. I was able to confirm this during this week’s local rainfall.

After the last bout of window issues earlier this week I did a bit more digging and discovered that a couple Tundra owners were having the exact issue that I was. The symptoms were the same, they identified moisture entering through the rear locking cylinder and rendering it defective as the likely culprit, and that a few guys fixed the issue by either disconnecting or replacing the rear locking cylinder (where you would enter the key to unlock or roll down the window from the rear exterior of the vehicle).

Back window is possessed- randomly goes down by itself | Toyota Tundra Forums

The process was ridiculously easy: remove the rear hatch interior panel, disconnect the wiring harness at the locking cylinder, secure the wiring to the back of the liftgate so that it doesn’t obstruct the windows track when you roll it down, and then put it all back together. And it worked!

While I can no longer roll down the window by using the key in the lock cylinder or lock or unlock the vehicle from the rear hatch, everything else relating to the window, the fob, locking and unlocking, works flawlessly. Medium term I may replace the cylinder for the ~$75 it costs, but in the meantime I’m perfectly satisfied.

Great info thanks for posting!

Even though I have a 3rd gen i'm pretty sure this is the issue i'm having. First time it happened was a few days ago while driving down the road in a rainstorm. Rear window just started rolling down by itself and I had to hold the up switch on the dash to keep it up. When I parked it rolled down a little and I couldn't get it roll back up until I turned the ignition on and off. For now I just pulled the fuse that controls the rear window so it wouldn't roll down when i'm not around. I'll unplug the rear key cylinder now and hope that fixes it. I don't use the features of that rear key very much so this won't be a big loss.