Help troubleshooting trunk electronics
 

Working on troubleshooting parking distance sensors after buying an E53 with a really wet trunk - sunroof drain is repaired- and I'm trying to figure out -what the small module is & which module is missing (wiring harness on far right in picture).
I have a PDC module on the way from ebay.

Small Siemens module is the towing module (AHM).

The spare harness may be for the air suspension module (EHC)?

Thank you, that makes sense. I pulled apart each module apart, no apparent water damage. Each PDC Sensor makes clicking sounds when the button is pushed.... the front speaker is unplugged, as it came, worth plugging in now that I repaired the seat sensor with an override.

Everything is back together & working now. Nice to have the PDC System live.

Well done and yeah, the PDC system is great. I have an overly-sensitive transducer on the front that I'll swap out next time I have the front bumper off (not removing it just for that!).

It's great until you install a cheap sensor! Or the body shop doesn't replace the seal on a damaged connector! ;)

I experienced that - cheap sensor will always fail eventually. Went through about 3. Gave up and got the originals from FCPEURO, never had issue since and it's been about 5 years now.

Didn't need to replace any sensors, cleaned the contacts on the modules, plugged everything back in, and it works!

Fantastic, thanks for sharing. Adding that into my basket of magic tricks ;).