I replaced the battery on one of mine when it got to the point where it wouldn't even start the car. With the new battery installed the key worked great at first, but the next day I got the "no key detected" warning. I swapped the battery again with another, thinking the first replacement must have been bad and it worked great..... at first. Then a day later I had the same problem.

So the issue thus far seems to be that when the battery is replaced it works immediately but a day later the FOB behaves as if the battery is dead. As soon as I pull the battery and put it back in, the FOB behaves normally for awhile, but later dies. I'm so confused. I was wondering if anyone else had experienced this- before I waste any more time troubleshooting. Right now I'm under the weak assumption both the replacement batteries are spotty.

PS don't go to radioshack. I got one off brand 2032 battery there for 6USD. The next day I got 2 energizer 2032's together at the grocery store for 4.50USD, quite a price difference. Not a lot of money but it stings getting ripped.

2007 Outlander XLS

 

That's what my key is doing (as described in post above this one). I tried one Radio Shack battery and then one Energizer. Both lasted one day and worked only erratically. I'm not convinced it's two bad batteries, but the fob itself is messed up. Probably will need dealer to fix, hopefully under warranty. I'll just have to live with it until I can make it to the dealer that's now two hours away. Mitsu really seems to be losing ground in the U.S.

Anyhow, there's a service bulletin that seems to describe what may be happening to our fobs with the new batteries. Doesn't appear to be anything we can fix ourselves.

Here's the thread describing. There were specific VINs supposedly associated, but mine wasn't included. My key, however, seems to be doing the same thing.
https://mitsubishiforum.com/forum/sh...ight=test+mode