I have a 2005 Grand Cherokee that uses a Navigation (Navteq on Board disk) It tells me that it cannot read disk, disk error or please insert disk. I have tried cleaning the disk, does not work. Because there is an error, I cannot get to any of the other functions, such as changing the time on the clock. What do I need to do, buy another disk? Trade vehicles?

SOURCE: FORMAT ERROR

You may have a bad floppy... Just like floppy drives in PCs sony floppys do go out. If you search around as I did (sorry don't remeber the link) you can find diagrams on how to replace the floppy and they are available for sale! I think we found some for $25 per. Good hunting!

SOURCE: navigation no longer works

I have the same problem.

SOURCE: Eject navigation disk in 2005 Jeep Grand Cherokee

Under the cd slot you will see a long thin rectangle that can be gently pryed out with a knife tip on the right side of the rectangle. under that cover there is a small button. push that and out comes the nav disc. Voila solved

SOURCE: 2001 grand cherokee disk changer

Does it still say disk error if you change disks?
If so, first guess would be that either a disk is inserted upside down in it's slot or the disk is too scratched up for the player to read.
But if it was playing that disk when you shut the engine off and said disk error when you cranked up again, it could be a fault in the player.
Sometimes CD player "eyes" can get dirty too. I don't know if this is your fix, but I hope it helps a little.

SOURCE: 2005 Jeep Grand Cherokee Ltd - Navigation System error

They did have problems with the disk and radio.Jeep has an updated disk(it happened to my brother).