Boot lid wont stay shut and it shows it open on the instrument panel, it shuts but still shows it as open and then pops open when you are driving

Run the fault code test and see what shows up, bet the Crank sensor code shows.

Close the boot lid.....
No, seriously now. It will probably be the sensor that is at fault. Don't know where yours will be. It could be in the lid lock, around the lid or lip of the boot where the lid fits to the boot opening normally under a rubber cover. You may be able to fool the car into thinking it is shut by bypassing the switch. Disconnect the wires to the switch (when you find it) and either leave the 2 wires disconnected (for a switch that is activated by the circuit being open) or connect the 2 wires together (for a switch that is activated by being closed). Try it without connecting together first and if this doesn't work then try connecting them together. Once you find the correct way then wrap in insulation tape to prevent any shorting out.
Remember though that this will mean that if you drive with the boot open you will get no indication on the dashboard. Also your boot light may not now work.

Some trunks have a lever near the trunk latch on the lid to disable electrically opening the trunk. Could be a short causing the trunk open switch to open the trunk. If it doesn't open electrically via a button then you have something bent and the trunk doesn't close properly.

use a round bar ( philips screw drive) , place it under the latch tongue and while opening the latch pull the bar out as if opening the boot
most likely that the latch is in the first lock position

Pop your trunk. Look up at the latch assembly on the lid and it should be brass colored but maybe a fuzzy white from corrosion from a humid sealed trunk. On the rear facing you side is a black plastic switch assembly that is screwed to the metal latch. This is the switch that turns on the trunk light. When the lid closes the hook/striker should press this switch in but if it's worn/misaligned, it can fail to open the circuit and shut off the light. You can just remove the bulb to stop it from killing your battery and the Ajar light on your dash will go out when you shut the car off.

Good luck,

Rebel Faggioli

the piece on the body wants adjusting

new lock required ,dont argue on this one ,they just give up the ghost

We had a similar problem with a 2008 right hand drive 407;ST HDI Touring. Suddenly the remote would not lock the doors and whenever you drove over 20kph then back under it would keep trying to lock itself. Anyhow after a thorough reading of the manual we discovered that the car will only lock if all the doors are closed properly. What we didn't realise is that the glass panel in the boot lid will also open outward like a flap, to allow smaller parcels to be placed in the boot without having to open the larger boot lid. We owned a Mercedes 300TE which didn't have this feature so didn't think to look for it. This was not closed properly. The handle/release must have been knocked when washing the car. Anyhow, once it was firmly shut everything went back to normal. Good as new.

Ken check fuses ..Is this one that you can open the boot from inside the car ?Try and hold the boot kid down while you set the alarm it might lock it