Key Remote Receiver Location and Power Feeding - Remote Key won`t work

[FredRC]

I`m trying to solve a Key Remote issue with a 540i.

Alarm works fine and gets activated and deactivated through the door lock. DWA red led in rearview mirror works fine and indicates locking and unlocking. Center lock button in the center console works just fine. Basically the entire Alarm System works fine with the exception of the Remote Key.

Battery is brand new, properly installed as I`ve already done a couple quite a few times. Key initiation (Key Sync) is being performed correctly, as I`ve done dozens of times before. Checked every single Fuse an Relay and everything is in order, Fuel Door Cap operating just fine.

Problem is, The Car won`t confirm the Key initiation after performing the procedure (insert key, turn, unturn, hold unlock, press lock 3 times). Usually I get the doors lock-unlock instantly, now nothing happens.

Which makes me suspect, after checking everything else, that the Receiver may be defective or unplugged. I removed the drivers C-Pillar and all the connections are Good. However the previous owner installed a Headunit and bypassed the DSP AMP

:

. Is it where the Receiver get its power from ? All the original modules in the trunk are disconnected, but all the original connectors are still there.

WhatsApp Image 2017-11-18 at 04.15.02.jpeg



Also I understand the Receiver must send info to the EGS, through which cable does it does that ?

OTIwMF9w.png">

I`m about to order a brand new key from the Dealer, but I need to be sure on what the issue is. Thanks

[StRaNgEdAyS]

Have you verified that the key is transmitting?
Most locksmiths have a tool that can check this, but if you had a frequency meter you could verify that it's transmitting yourself.

Sent from my G8141 using Tapatalk

[FredRC]

I don`t have a frequency meter, I tried using an AM radio tuned to its lowest frequency. Keys from my other cars would cause interference, but the 540i key won`t.
Thats not a conclusive test of course. However, knowing where the Remote Receiver gets its power from would be the easiest route to pursue right now.

[edjack]

F53 supplies the remote entry (FZV) receiving amp.

Depending on MY, the keys transmit in the 3-400 MHz range. http://www.realoem.com/bmw/showparts...89&hg=41&fg=50

[FredRC]

Found this: "According to Bentley manual. Fuse 53 FVZ (Remote entry) antenna amplifier,Tailgate lock switch,Central locking fueltank access door,Trunklid motor relay,Diversity and window motor relay"

Everything on this list works fine but the FZV (which I haven`t directly tested). Its fair to say that since everything else works, the key remote its probably the issue right ?

So the FZV draws no power and has no relation with the DSP AMP/ CD Changer that was disconnected ?

[Qsilver7]

Back in the original post there's a diagram of the amps in the C pillar. That diagram was taken from the audio section, thus all the cables etc are identified as such.

But if you look at item #1 in that diagram (right/passenger side)...there are empty cable connections. Since we know the FZV antenna is incorporated into the rear glass...uses the same amps as the radio antenna...but feeds it's data to the GM (the main control module for FZV &DWA)...perhaps on the sedans...the FZV amp is on the passenger side similar to the illustration below of the e38's rear antenna set up:



You can see in the illustration below of the Touring (applies to SAVs too)...that a cable runs from the FZV amp in the D pillar directly to the GM. I'm sure the sedan is probably the same...but the correct amp & cables in either the right or left C pillar needs to be checked:

[FredRC]

Thanks Q, your diagrams are always of great help. At least in the 540i 2002 the FZV antenna (Black box) is in the drives side and the the diversity antenna (white box) is in the passengers side, I`ll recheck both tomorrow to test for power feed an disconected cables. I`m also suspecting the key board might be done, I just noticed a broken transistor under the ECE sticker. Will update