I purchased a 2002 CLK AMG 55 and am troubleshooting the non-operational soft top. While doing this, I needed to use the mechanical key to open the trunk so I could test some sensors. When I tried to use the either mechanical key from the two FOBs I have to open the trunk, I discovered that neither key will insert fully into the lock and therefor will not unlock the trunk. I tried both keys in the door lock and they both work fine. Is there anything I can do to resolve the issue? Is there a way to tell if the lock has been replaced?

 

Do a forum search...sooo many threads on this and how to fix...I always kept one backseat latches unhooked (red tab shows) in case I can't get into trunk the normal method

 

Appreciate the reply...but I have been unable to find any similar threads on this forum. Could be because of my search skills...would you be so kind as to help me locate threads on how to correct my problem?

 

Insert…turn counter clockwise…push……flood the tumbler w wd40…don’t break the key…might have something caught in interior latch…if you can get into trunk through rear seat, push safety green button to open

 

@cindyclk thanks for the reply. Unable to turn the key ccw because it does not go all the way in...like it does for the door.

 

Hello again Phydeauxman,

As discussed in a related thread in regard to the repair of your power roof , when the pneumatically operated central locking system would not allow either the key fob or center console remote trunk release to open the trunk , the solution would be to remove the mechanical key from the key fob and use it to open the trunk, as described in your owners manual.

The procedure requires being able to rotate the cylinders tumbler 45 degrees CCW, followed by pushing it inward, so that a lever affixed to the rear of the tumbler, will manually unlock the latch.

When the mechanical key won't fully enter and/or rotate the tumbler in the direction shown, it's because it hasn't been used since it left the factory, several decades ago and during this time-frame, the cylinder's metal internals have succumbed to dirt, rust and/or corrosion and seized from non-use.

Unfortunately, the last picture you included in the power roof repair thread (hyperlinked above), clearly shows this.

However, with persistence, the vast number of owners have been able to successfully free up the cylinder's tumbler mechanism, by just using an appropriate can of aerosol release agent and then spraying the key as well as directly into the key-way, followed by ample wiggling and moving the key back and forth.

You'll likely need to repeat the procedure a good number of times to free up the tumbler and it's pins.

In the past, others have used WD-40 to free the lock, but it's petroleum based, which then leaves behind a sticky residue that will attract dust and dirt, or a Graphite spray because while it left behind no sticky residue, but an excess of Graphite power can harden and over time, gum up the cylinder.

The technology of spray solutions to free up struck lock cylinders has since significantly advanced and you'll learn more about which new products are best, upon searching the internet.

As diagrammed below, the trunk lock on cabriolets operates differently than the coupe models.




During MY 2001 production, trunk lids were fitted with a green emergency trunk open switch, often referred to as a hijack button.

It works by electrically powering the A37 pneumatic pump to unlock the trunk however, it does not perform the same mechanical unlatch as the push inward of the fob's metal key, nor is it readily accessible because of the cabriolets roll-bar assembly.

By design, to prevent a collision between the trunk and soft-top compartment lids, whenever:

-the roof is in process of being opened or closed
-the roof is closed, but not properly locked
-the roof is open, but not properly locked

The N52 soft-top control module cyclically sends the following CANBus digital messages to the central locking module, "SOFT TOP CLOSED", "SOFT TOP UNLOCKED" or "SOFT TOP OPEN", so that the pneumatically operated central locking system will no longer allow either the key fob, center console remote trunk release or the trunk lid emergency button to open the trunk, which is why you will need to use the metal key for access to the soft-top components located in the trunk.

Lastly, if you are not able to get the mechanical key to work, as a last resort, the following procedure by Aussiesuede, details a procedure where you will be able to open the trunk.

 

@Serndipity thanks for the additional info. I have been soaking the lock with Kroil penetrating oil for days and have been trying to work the key in and out to get it to go in all the way. No luck. I truly believe the lock cylinder is damaged, preventing the key from going all the way in. Is this a replaceable part? I found a video on how to get the entire trunk lock mechanism out of the trunk lid but no how to replace the cylinder so not sure what the replaceable part is.