My 2003 745 li trunk won't lock. It will go down on it's own, but will not lock. how do i manual lock my trunk?

Something broke on the lock mechanism. In order to open the trunk, you will have to remove the rear seats and try to access the trunk area. Once you are in the trunk, you should be able to manually open the lock and investigate what broke.

Remove the back seat and crawl through and manually release latch from inside the trunk. the replace the lock cylinder or the lock cylinder retainer clip.

I had the very same problem with my 2002 Saab 9-3 after I manually moved the trunk latch to the locked position "out of curiosity..." Then I noticed there is a handle you can pull to release latch opening it up! Very simple remedy... It is a glow in the dark green plastic handle hanging down when the trunk/hatch is open dead center, just in slightly behind latch... Gently pull handle until you hear and see the latch click into the open position...Let me know how You make out. BTW: Toyota Camry has the same set up,same color as well...lol Good Luck!

Trunk lock assemble could just need oiled,try that first and if no help it may need to be replaced.....please rate this post and good luck and hope info helps.

Lower the back seat and crawl into the trunk and see what the latch is doing when you activate the key fob. the trunk lid will have to be open to enable any repairs. Also an emergency release cable is probably visible (yellow handle) inside the trunk and will Open the trunk lid.

hi some models do have fold down seats, but if yours does you would know, if you have to get into the boot to manually open the lock remove the lower back seat by 2bolts near floor level, then the upper seat by 2 or 3 bolts that will now be exposed, then simply lift out

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