Locked my keys in the trunk of my 2004 malibu but car is unlocked is there a way to access the trunck by going in through the car

Yes.

There is a relay in the rear fuse block for the trunk release. marked trunk relay #36. It is marked on the under side of the lid. If you knew how they worked you could open it by jumping pin 30 to pin 87 in fuse box. on the side of the relay is a diagram of what pins are what . This system uses an electronic control module called ( the BCM ) body control module .When you push the inside release button , that sends a signal to the BCM ,then the BCM activates the relay opening the trunk . Well that won't help ,you won't believe where the fuse box is ! Fuse Block - Rear
In the rear compartment, behind the left wheel well. You could jump the wire at the BCM that goes to the relay. Can't you pull down one of the rear seats to gain access ?

Is you car unlocked ... if it is you may be able to go through the back seat. If you remove the bottom part of the seat it should expose bolts to the back rest section of the seat. Once that is off there may be a divider of cardboard .... look for fasteners and remove that. Get your keys and put it all back together. Does the car have a trunk release in the glove compartment or other location? If the car is locked then you may have to call a locksmith.

Hello. The electronic opener needs new battery. Change it and it will open. The dealer can get you a new key. Get the Vehicle Identification Number & Bill of sale or good proof it is your car and they will help you get a key.

fold back seats down reach in trunck and pull handle

can you get access through rear seat

get in through the back seat

A lot of today's cars have seat backs that fold down to allow access to the trunk. I guess you would of already tried that. Just a thought. The only other thing I can think of, besides calling a locksmith, is to see if there is a blown fuse for the remote opener.

You will need to locate IP5 pin 16 on the General Electronic Control Module
that sits RH side behind your instrument panel (UK Car) .
IP5 is the large brown 23 way connector that goes into the module.
Take this pin to ground then your boot will pop open.
Check out http://www.bluejag.co.uk for general infomation on Jaguar X type

I have a corolla 2003 and I had the same problem. I turned the key to the left and the lock turned left, engaging the valet parking mechanism. I could not turn the key to the right and could not get access to the trunk because the lever next to the driver seat was disengaged.
The way I solved this problem is as follow:on the back driver seat I pulled the back seat forward to leave an opening and snick my arm in the trunck. Then I grabbed the cable used to latch the seat and I pulled forward, i.e. toward the front of the car. The cable is connectred to the trunck so that it can be disconnected easily if pulled towards the front. If you pull towards the back it will remain attached to the trunck. So grab the cable an pull towards the front, and it will release itself. Since the cable is flexible, you can pull it out of the trunk from the same the opening you put your arm, and then disenagage the driver back seat. Fold forward the back seat and get into the trunk and use the lever in the latch of the trunck to open it. The turnk will open.

If the lock does not turn, you need to disconnect the lock from the mechanism, so that the driver seat lever can start working again. To do this, and with the trunk open, remove the cover holded by nine plastic pins. Do not break the pins. After removing the cover, you will see the lock holded by two nuts. Remove the nuts with a rachet. The lock will be loose, and disconnect the lever that connects the lock to the latch. At this point the driver seat lever will start working again. Close the trunk and verify that the driver seat lever opens the trunk. Now you can open and close the trunk , and have time to call the dealer for a new lock.
Good luck.