Mine went flatline yesterday afternoon while in traffic on a Phoenix expressway. Reset itself and seems to be working fine today.

 

It'll flatline above 115 degrees, someone said in a post quite a while ago.
Mine flatlines in Tucson kind of regularly in summer.

 

My temp read-out went flatline this afternoon and temp was only about a 100.
When it came back on, it was stuck at 90 even though I know the temp was higher. Also since it flatlined three weeks ago, it seems to respond very slowly. I back out of the garage in the morning with the read-out at 80 and temp is 65 ... it takes five minutes or more to reach 65. Anybody had this? Time for fuse 7? Time for the dealer?
Thanks in advance

 

How long does it flatline for?
A few seconds on startup is what mine does.
There's a pretty sophisticated algorithm that it uses that sometimes gives different readings than what you expect; it has to do with coolant temp and how far/fast you have driven the car; it takes a while to change because the algorithm it trying to make sure the reading isn't affected by engine bay heat. It'll always flatline above 115 degrees.
In traffic, the temp could be 115. It was 105 in Tucson today.
What you are describing sounds like normal operation to me.
Couldn't be the fuse; it wouldn't work at all.
...Take it in if it bugs you.
...If you take it back to IL it'll be fine. Sorry, I couldn't resist.

 

I just had this issue occur. I located the sender behind the bumper, and it was physically undamaged.
I read pulling fuse #7 and/or fuse 21, might solve it-no go.
On a hunch, I pulled fuse #5 (another 7.5 amp fuse), for a few seconds, and I am back in business.
Perhaps I am misteading the fuse # key on the fuse block cover, but I pulled#7, and then # 5, and # 5 was the winner.