2006 S-350
Started out with the SRS red warning dialog. had a sensor under rear seat fixed. Lasted 3 weeks...
Then the trunk would not go all the way up when opening the auto lift with key or trunk button.
Then started to not come down so well.
Eventually it had to be lifted and closed manually.
Took out the pump from the right rear quatrer panel, added fluid and it worked again. I can't find the name/info (part number etc) for this for the car.
I think if it is replaced, the trunk will work again.
I saw in another post how they could be related to the SRS warning?
Ideas?
Then, off to repair the Airmatic system.

 

If you ran the hydraulic pump dry it may be done, if you call Europarts.com they will get you one if not in stock and might be an OEM part only so they may need to order it for you.

remember the hydraulics only bring the trunk down then the PSE pump finishes the close, so you can bring it down until it latches once then listen for an air leak, if you hear it, it's leaking. This works for the doors and rear headrests as well as the seat bladders. If the pump doesn't run you can reset it by pulling the fuse right rear floor below the seat for a few minutes.

PSE pump is in trunk on front left. it will shut down any of the systems or doors-trunk if leaking.

 

Sorry, forgot the SRS, if you drive with the trunk partially open the SRS light will go on, mine did, another time mine went off and it was fixed by fully unreeling each seat belt to the stop and slowly letting it retract. I did all four belts.