Cant unlock the trunk lock in my 2005 honda accord

Where else do you have locks? A locking glove compartment often has a separate key. The main key is supposed to open the door, open the trunk and start the vehicle. The other key is a Valet Key, the key is intended for people to give to valets to park their cars or to repair shops to use. The valet key will open the car door and start the car but will prevent someone from unlocking the glove box or the trunk.

the valet key doesnt have a transponder chip in it, so it will allow physical turning of keyways and operations, but will not disable the alarm and often wont disable the immobilizer.

sorry to say i think you will need to get an autolocksmith , or main dealer to get you a functioning key with transponder chip mapped to your cars rfid system that will allow alarm to be enabled /disabled

Valet Key ? 0nly does the drivers door & ignition

check trunk fuse

There are 3 phases to fixing your car's trunk lid release problem.

Phase 1: First check the fuse - once you know that's OK, then proceed to phase 2 (below).
The fuse for the trunk lock is
the bcm (pwr) 15A fuse in the instrument panel fuse box (behind panel at drivers right foot)

Check that fuse, as it is the power supply for the button on the dash that sends power to the actuator in the trunk.

Phase 2: Get the trunk open (without taking it to the dealership).
If you have remote keyless entry to the trunk, you could try that - but with the actuator
dead/dying, it shouldn't work.

Here are a couple of ideas to try to enter trunk while (a) actuator isn't working, and (b) all
valet lockout features (designed to deny valets access to the trunk) are in the "Lock" position:

There is the lock cylinder, which you stated is not functioning - put the key in, and it doesn't
turn. Just to be sure, consider: lubricate key with Graphite lock-type lubricant, and retry.

The trunk has 2 valet safetys...the locking rear seats which require access to the trunk to unlock, and then there is a valet switch in the trunk that locks the button on the dash from working to keep valet parking attendants out of the trunk. That may be in the lock position.

You can try accessing the center area of the fold down rear seat and see if you can unhinge the rear seat from there. Maybe reach in with your hand, or an extension-type tool.

there may be a way to fold the hinge away from the seat back so it can be removed from the hinge and give you access to the safety latch in the trunk and open it that way (white handle in trunk).
The white-handled safety latch release is desiged to prevent accidentally trapping children, and
if you can pull it with your extending-type or grasping-type tool, the trunk will open whether or
not the actuator motor is working.

Phase 3: Replace the Problem part.

Your failed part may be either (1) Trunk Release Relay, or (2) Trunk Lock Release Switch

My Satrun ION manual doesn't cover either of these parts, and the online parts houses, e.g.
http://www.rockauto.com/catalog/x,carcode,1431624,pgname,Electrical-Switch%2B%2526%252338%253B%2BRelay,a,search.yahoo.com%2BSearch%2Bfor%2B2004%2BSATURN
fail to provide instructions. One of those times a mechanic has to t=rely on his/her native
handiness and/or experience.
To identify which of these parts is bad, locae the Trunk Release Relay (call your dealer parts
dept. for helpful tips on finding it), then operate the dashboard trunk release button with your
ear close tothe relay - if it makes a noise, the problem is the Trunk Lock Release Switch in
the trunk lid, otherwise its the relay.

1. Open trunk
2. Place latch in lock position
3. Pull inside trunk release to see what isn't moving
4. If trunk key won't turn, the key may be worn out and need to be replaced

If you hear the sound of the electric latch switch, then it's working but stuck somehow. Just put the key in the switch and turn it to the right and then pull up the trunk or ask someone to help you. it will open. I tried it today and it opened with me. It was stuck from inside by some kind of a broken plastic pieces. Just removed it and now it's working fine. good luck

It either has had the trunk replaced and the old cylinder wasn't installed, or the key you're using is the valet key. See if you can lock/unlock the glovebox. If you can't you're using the valet key. If you can, your trunk lock cylinder is not original.

There are Valet keys (often with a green knob) that will
only unlock the front doors and the ignition but not the
glove box nor boot/trunk.

When either the front door locks or the console button is
pressed, all the doors should lock. Likewise, when either
front door is unlocked, all the doors fuel filler lid and if
selected, the boot will also unlock.

Boot lock has three positions. Unlocked to the left,
automatic with the doors in the center, always locked to the
right. Simply remove the key in what ever position you desire.

The locks can get confused and not work correctly. Simply
sit in the car and manually lock all the doors. That will
usually get the locking module sane again.

Your Grey key is the valet key.

The Grey key will not open the glove compartment nor the trunk, BUT you have to lock the back shelf and remote trunk release handle in the car, and the glove compartment with the black key first.