I have a 04 s 500 now owners manuel and I don't know where the battery is and I can not get in trunk even with the little key in the remote I have no idea why the battery is dead it was fine a few days ago

I assume the key works or you would've mentioned it. So my first thought was fuses, you should pull the fuse for the trunk mechanism, put in a new fuse even if that one still looks good, if that doesn't work, try the original fuse to see if the new one was a dud. Either way you'll know if that's the problem or not. Another thought, it could just be the remote. Some car makers saved some money by removing the mech. connection from the handle to the lock, since the remote receiver and motor were already there. Pushing the button would send the same signal out as the remote. Put new batteries in the remote. One last suggestion, read the owners manual and/or website, and find out if you can simply re-set the code/frequency to default. Hope that helped, Grimm

There is a key trunk access behind the drivers seat.
It's probably your battery. Even if your battery shows that it is close to 12v sitting, I've found that the amperage comes in to play when trying to start it.
Good luck,
Patrick

You can get back into the trunk, this is tricky but i have done a few times use the key in the trunk key hole and turn key one way all the way and then turn the other way while slightly lifting on trunk.

try it a few times it is tricky but trunk will open, there is something about the way the lock is set up due to it using battery voltage to open it, but with out battery it is funny, do not give up, turn key all the way both ways, the key will turn a little further to the left i think to open trunk. good day. let me know the out come.

I would check the owners manual or with Cadillac - its possible the remotes lost part of the signal and need to be reset. It sounds like the receiver is not getting a signal from them by using that button.
Could be the receiver too.

You do not need a remote to deactivate the factory system, it is deactivated when you insert the correct Key to open the door and start eh van.

If you have never replaced the remote's battery, it may be time. The 'coin' type batteries do live long but not forever and mfr.s typically suggest that the lithium cells have a 'shelf life' (unused) of more than five years.
I don't know the construction of your remote so don't know if the battery is user-replaceable or not and if not, the dealers usually take advantage of customers when they can. The batteries alone are cheap costing a few dollars at worst.
If you have the 2nd remote stashed somewhere, you might try it if it has not been in use. Even then, the battery may quickly be depleted in the spare too.

on the trunk there is a key hole buy the back lic plate there may be a little cap you need to pop off to see the key hole

I had this problem on my 2005 s type.The problem was the valet switch in the glove box was in the lock position.i pressed it ,and now it works fine.Try this..

you can charge the battery from the engine compartment. check your owners manual that is the correct place to jump and to charge the battery.

u have to take the valet key out of ur remote. It will open the trunk, it can just be very hard to turn but it will i do this all the time.