exhaustgases

So is it an electrical solenoid that releases it or an air compressor?
Sure wish a service manual was available for these cars.

shadenfroh

It's vacuum operated along with the other parts of the central locking system, the rear headrests, the AC flaps.

What's your problem?

Serndipity

When you use the center console switch or the FOB, trunk unlocking is vacuum actuated (e.g. moves a lever, unlatching the strike plate).

When you use the metal key to open the trunk, after turning the the key 45 degrees counter clockwise, the same lever is moved manually, releasing the lock, when you then push the key inwards.

exhaustgases

I heard the fob and inside switch won't open it. So how is the vacuum created?
A pump? You sure couldn't depend on the engine vacuum lasting forever.

shadenfroh

First you try the metal key to rule out a mechanical problem in the latch. Careful with that, it could be stuck if the owner (I guess it's not you) has never used it.

If that works, the problem lies with the PSE Pump or the vacuum lines. Try to open the trunk with the button and listen for a "whirrrr" sound coming from the trunk. If you do hear it and it goes out after a few seconds (6 if I recall correctly), it's a vacuum leak. If you don't hear the sound at all, the pump is not spinning, meaning a faulty pump or electrical problem.

Rear head rests, central locking (+ fuel filler flap), ac vent flaps are all vacuum operated. A problem in one of them is generally a vacuum leak, a problem in all of them is generally a pump.

If pump is faulty disassemble and clean it first, before buying new/used one.