ArMaNi S500

Ok I know I should've sold it by now but just didn't have the heart to, but my '00 S500 with 135k miles has a problem. Recently while in transit I'd notice a problem and the ESP light comes on and my time/date completely reset. This happened twice. Then the other night I came home, as soon as I shut off the car I noticed none of the electronics were working in the car. (Dome lights, unlock, etc) I'm hoping it's a loose battery terminal but I can't even access my trunk because my manual key is half broken from the top. I have a thin black thing that resembles the shape of the smart key with a pull-out manual key but that doesn't work on my door. (Don't know what it's for) Is there any other way to get into my trunk? Is it even the battery or terminal? Should I just buy one of those key-bump things and break into my own trunk? Someone please give me some advice! Thanks!

brakel8

Sounds like you may have a water leak through the blower motor and the carpet on the passenger side is wet and the rear SAM is all corroded from the water which would affect starting, door locks, lights, audio etc or it's just a bad battery or alternator. There are many players that can cause this issue.

Gullwing

If it is a dead battery.
You can take up the rear seat cushion to access the rear sam (under right rear seat). You then can access the main power cable to the rear sam, use another batter to apply power to the cable and find a ground. You then might be able to unlock the trunk and open it.
Careful!!!