No auto-open trunk, but many parts present?
 

Just bought an '09 535 E61 and as I'm looking around the vehicle I'm a little confused about some parts. So for example, under the spare tire where all the control modules are there is an HKL unit. Then, when I go through iDrive settings I have the option to select how high the trunk will open, the liftgate has the button on it to auto-close, and, when I did a scan with ISTA+ for fault codes I get a code saying "HKL: Angle-of-rotation sensor". However, I do not have a hydraulic pump in the back. When I do a VIN decoder I get "S316A automatic trunk lid mechanism" so I'm wondering if someone had a problem with the system in the past and switched it from the hydraulic unit to regular struts. Any thoughts? I can add photos of the lift supports if that's helpful.

Edit: After looking at http://tcbf62.blogspot.com/2018/02/b...hydraulic.html I'm thinking I might have to dig a bit deeper to verify that I don't have a hydraulic pump. All I did was open the panel on the driver side, I didn't remove the satellite radio unit to dig deeper.

When I was purchasing mine the used car dealer said that because they often break they will just replace the hydraulic strut with a gas one and call it good. Did you pull off the left panel all the way to the back seat. The Pump is way back there.

No, haven't had time yet to open it all up. I did take these photos of the struts last night. I don't even see where the hydraulic lines would have come through to connect to the strut.

https://cimg5.ibsrv.net/gimg/5series...595ccb9a6a.jpg
https://cimg6.ibsrv.net/gimg/5series...6b6f57aa84.jpg

Is there a lot of friction when opening the tailgate?

I would say it is fairly stiff compared to my 2002 Golf's tailgate. It's not really all that stiff to open (the struts are strong) but you do have to push a bit to get it all the way down. I changed the iDrive opening height settings and it has no effect (obviously).

I just meant to open. Does it lift itself up or do you have to really force it. When I disconnect my battery to do work and need to move mine it is a pain. It looks like the original strut was removed I believe. I cant check mine as I am at work. I will look tonight. You can check the part code on the strut and type it in to google to see what models it is for.

You should have something that looks like part 51-24-7-163-662

Thanks for the clarification. It lifts itself up just fine. There are two struts so it wouldn't surprise me if someone else removed parts of the system in the past and put in two regular struts. I had my battery out the other night and the tailgate had no problem staying fully extended all night.

Well, I finally opened the side panels and saw that there is no hydraulic pump, but the ends of the pressure lines were there wrapped in a ziploc bag. Clearly it failed for a previous owner and they removed it all. Even replaced the plastic trim piece around where the upper end of the strut connects to the body as there is no hole for the lines to go through. Ordered a used pump and cylinder for $380 and we'll try our luck with it. Certainly do not need this feature but it also grates me to have a button that doesn't do anything on my car.