Central locking bodging by previous owner
 

I've recently bought a nice 530i manual, albeit with the N53 engine, but all is running well. 78k miles, very nice condition.
However... I received two fairly well used third party plippers with the keys, and the rear window did not work. I assumed that this was because the keys were expensive, and recoding would be too.
On further investigation, I have found out about the diversity antenna, and dreaded wiring loom problems. As per a bunch of googling, docs and youtube videos, I discovered how to open the rear window with a coat hanger, without cutting into things. and found that the switch had been disconnected. I already had new one, so replaced it. Keeping going, I found that the loom wiring (2nd from right) was in a bad way - it had previously been repaired with a fair bit of tape. I removed all this, and replaced the lot with silicone wire, from the roof, into the spoiler, using solder butt plugs.
Now the window works, and weirdly, the tyre PDC which had been greyed out, has come back to life.
Now... I have fine DAB and FM reception, but the keys don't work. A nearby locksmith has confirmed that they are sending a signal.

My next port of call will be the diversity antenna. However, I would like to get to the bottom of the third party plipper. All it does is activate the central locking. The alarm is not activated. If I use the key, then the security system works as expected, so I am guessing that the third party plipper is just activating the central locking.

Any ideas on where this might have been done within the car? I'd like to get the antenna working again, then remove the third party plipper bodge. I guess this was put in (and the window switch unplugged) because the previous owner was quoted frightening numbers to fix it all.

it's a good thing you fixed the microswitch from the tailgate/glass lid, because in order to get to the diversity antenna, you need to have that glass lid opened.
here is a good diy to get to the antenna on a E61: https://www.pelicanparts.com/techart...al_Booster.htm

the thing could have water damage, but you can try to give it a clean, as per the diy above, good chance to bring it back to life.

surely the previous owner did not fix this and installed a third party alarm or whatever, to bypass the car's central locking system.

I had the same problems with the wiring loom, also my central locking was not working when using the car's key fob, but my culprit was from a broken wire, from the diversity antenna, somewhere in the hinge, the antenna itself was ok, no water damage, so if you say you checked and repaired all the wires, well... it has to be the antenna.

Yes - and getting the glass lid opened with a disconnected switch and knackered wiring was not easy. If I'd not found out about the small hole in the lock you can probe to ping open the glass, it would have been a nightmare. Videos are here, if they help anyone: .

I suspect the antenna, which I will look at. Once fixed, I would like to remove the third party system. I think it is triggering the locks in the same way as the locking button does, so maybe I'll find it in the glovebox somewhere...

Fixed
 

Window looms LH and RH completely rewired (except for co-ax and wiper pipe). Had been previously fixed, was going south.
I've now put in silicone insulated wiring as suggested elsewhere.
And there was corrosion in the diversity unit... After an attempt at fixing this, I bought a new one.
Now everything is working once more :-)