Xoutpost.com - Water Ingress Issues

Car is 2008 X5 4.8i. ~170k miles

Current issue up first:

One day I noticed the rear seat footwell carpeting was soaking wet (during an all day rainstorm). Opening the rear passenger door, there was a splash of water that came from the door, and continued dripping from the drain ports. The underside of the interior door panel was showing sides of mold/yuckiness but did not actually feel wet. Some googling leads me to believe the vapor barrier needs to be replaced, but there was some argument to that, and the door is designed to leak out water and it's normal. However I don't think the amount of water that splashed out is...

I have checked and unclogged the sunroof drains, so I feel confident there. The rear seat footwell is the only area that is getting wet.

Anyone else run into this issue? Vapor barrier seem like a good place to start? Anything I can inspect to help me pin-point the issue?

Long story and history of issues:

Sorry this may turn out to be long, but the debugging/fixes may prove helpful to others in the future.

About a year ago, my wife and I ran out for some errands, and mistakenly left the sun roof open, for at least 3 weeks. It's her car, since day 1 of COVID she's been working from home, so we didn't notice until we went to drive it again, and it was pretty soaking wet. The trunk area was pretty well flooded with inches of standing water in the rear side compartments (under the plastic storage areas), and a small bit of standing water in the spare wheel well.

After some time doing our best to shop vac the water out, dry it out with heaters or opening it up on nice days, we seemed to have it fairly comfortable, but that's when I noticed issues:

- No radio/chime/any sound - SOS error
- Intermittent passenger seat belt warning
- Tailgate motor not engaging
- AC not working (noticed later in warmer weather)
- K CAN line fault

I would drive it every once in a while to keep the fluids moving and battery charged (I also have a trickle charger I hook up every once in a while). A couple months ago we opened the front passenger door and there was puddle on the floor mat. I was able to clean out the sun roof drains (passenger side front was completely clogged, passenger rear was slow), and the front of the car has been dry since. Heavy duty weed wacker line worked well for the rears, but was getting jammed on the fronts. Compressed air worked best there.

Recently I've made progress on fixing some of the issues:

- No radio/chime/any sound - SOS error:
- Resolved through MOST bypass loop around the TCU. Presumably a replacement TCU would fix this correctly and restore whatever TCU functions I've now lost. Side note I really have no idea what the TCU is for.

- Tailgate motor not engaging:
- Resolved through tailgate control module replacement. Debugging included removing old tailgate control module, opening the plastic case, and physical observation of all the corrosion inside.

- Intermittent passenger seat belt warning
- Goes away when the car is completely dry (or turning seat heater + ventilation on). Fault code scan showed occupancy mat issue, so that would be the fix if we continue to have issues.

- AC not working (noticed later in warmer weather)
- Currently unresolved. Fault code scan indicates some condensation/moisture sensor faults (no communication). Possibly related to K-CAN line fault. Some google hits that there might be an issue with the JBE, and others have reported corrosion issues after water ingress. I did not see any when I checked it.

My first diagnostic steps was checking fuses. All look good. I've replaced all cabin air filters and will do again after it gets driven more. We also purchased an upholstery cleaner. Doing our best to make sure there's no lingering aroma....