Trunk release and fuel door does not work

check fuses and relays and get a new key cut their is no EMERGENCY release

It gets power from right hand maxi fuse block , Ignition 1 fuse, 40 amp. through ignition 1 relay.
1998 Cadillac DeVille ' DeVille, Eldorado (VIN E/K) Service Manual ' Body and Accessories ' Wiring Systems ' Component Locator ' Document ID: 519143
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Engine Compartment, Near the Left Strut Tower

Which fuse were you checking? There are two fuses in the trunk release circuit - one underhood (ALDL) which feeds the trunk/fuel door release circuits via the valet switch and also the ALDL circuit; and one under the back seat (BODY fuse) for the trunk release.

Unfortunately, relay control signals for these releases run through the IPM (Instrument Panel Integration Module) which handles the release buttons on the dash, and the RIM (Rear Integration Module), which receives these signals from the IPM and handles them and the trunk release button on the keyless remote.

If the fuel door release is working at the dash and the trunk release is not, the ALDL fuse should be OK and the problem may still be with the BODY fuse, trunk release relay or wiring. If that isn't the problem, then I suggest you check for IPM and RIM DTC's (error codes).

check for blown fuse for int. lamps, locks fuse and 2 relays. do any locks work?

Hello: Check the fuses in the fuse box under the hood, drivers side also check the fuses in the trunk fuse panel on the drivers side. If the tail light fuse is open that will keep the instrument lights out also.

So the key wont open the trunk? there should be a pull cable in the trunk near where the gas door is to open the door.

That's because he likely cut the power wire to these when he was looking for power sources for his stereo.
GM almost always has at least one empty spot on the fuse panel that will provide a power source for aftermarket equipment such as stereos. He'll have to put an in-line fuse in it. It should be marked ACC. If not a test light will easily show him where he can draw power from the fuse box. Hope this helps.

rear fuse panel..... convenience fuse, 20 amp

with a 12 volt test light check fuse ( #22 not entirely sure, or in the 20's ) 20A fuse blown. controls both trunk release and fuel door. Hope this helps.

let me assume u have not checked the fuses, meaning in al places the fuses are!, try,under the hood,under the dash and behind the panel behind the rear seat in the trunk, look in your owners manual for these locations and the particular fuse u have trouble with. good luck,hope we helped!