[SOLVED] mysterious water leak and now MMI is flakey

I took the S6 up to the Cameron Highlands (MY) last weekend and (while parked) it got caught in a torrential downpour. It was literally raining buckets for about 1 hour.

Later that evening when the rain subsided to just a sprinkle, I discovered about 1/2 inch of water in the front passenger footwell. There were some drops of water up top by the overhead light cluster and immediately below by the left side of AT shifter.

The windows were closed and so was the moonroof. I cannot imagine how that volume of water ended up in the footwell. None of leather seats were wet. Where did the water come from?

I checked the sun roof drain on the front right corner by pouring water through it—i found the water draining out the back of the front right wheel well.

A side-effect of this drenching are some random electrical gremlins. The dash reports a parking brake malfunction, and the MMI system comes to life for about 3 secs on startup—then the whole system abruptly shuts down. It seems like a bad connection somewhere.

I’m hoping you guys can give me suggestions on how to get to the bottom of all this.

I would pull the center console out.

I had to do this to fix a sticky button issue, and my ebrake was stuck on because the switch stayed stuck in the on position.

There is a youtube video of the removal, it’s the same as a 4f c6 a6. Wasn’t too bad to do, did it in about 40mins.

https://youtu.be/os1TO0WY1u8

The MMI controls themselves sit on a circuit board, so you could probably also try just some compressed air in there to help it dry out. If it were me I’d pull it out and clean it with alcohol then let it dry.

as for the wet passenger floor, I don’t know if there are modules in that section like other Audis (Q7 or B6 S4). I had a nasty flooding of my B6 S4 where there was a few inches of water in the footwell, and it was left too long and the wiring harness started to corrode. The comfort control module was in that side and it got fried along with a ton of other components.

Hoping this isn’t the case for you.

Side note is there any insurance cover for flood on your car?

It’s just weird. I get a flash of the logo screen or the backup camera when I start the car—then the MMI cuts out. The red LEDs on the MMI buttons are all dark now, but for awhile they would all light up to full brightness before going dark. I’ll probably follow your advice and remove the MMI to have a look.

As for the water, I was able to soak up most of the water when I discovered it. Fortunately, I had a bag of towels in the trunk. And it’s all dry now. But can anyone speak about whether there are any sensitive electronics below the passenger footwell?

My MMI behaved this way last week after I disconnected my battery to do a throttle body adaptation.

I pulled all of the MMI related fuses. I didn’t find anything. When I keyed up the MMI was back to normal. I have no explanation…

Maybe disconnect the battery and see if you can get everything to reset. Can’t hurt.

Did you pull the full panel to expose the green water drain system. There is a good chance that the water drain line itself might be leaking. It can still work and drain but there might be a small weep hole.

Which panel is this?

I can definitely confirm the MMI is on the Fritz so my theory is that all the water came in through the sunroof. I just can’t account for how the water only collected in the passenger footwell…

Thanks for the video. I think I’m going to have to take out the MMI and inspect.

Is there a trick to removing the rear console vents without the special tools? Or do I have to buy them?

I made the tool out of a coat hanger. It’s just a hook like what he used in the video, I used 2 pliers to make the 90 degree bend that was super short. it needs to be no more than a 3/8 of an inch

brilliant MacGuyver! That’s why I love this forum.

I managed to take out the center console as per the video. It looks really clean from the bottom. No sign of any water damage.

  • I have disconnected the battery to reset the MMI
  • removed the center console to inspect the MMI connectors

https://i.imgur.com/1TJumYu.jpg

The current observed behavior is a MMI boot screen on start, then a black screen of death after about 3-5 sec. Occasionally, the radio will come on before shutdown. But the MMI controls do not work–radio volume only seems to respond to the steering wheel control. And the red LEDs do not light up on the MMI buttons.

It can’t be a fuse because I get a startup screen every time before it shuts down,right? Is there anything upstream that I should check?

I don’t know for 100% sure but if you look under the carpets on the passenger side there is the MMI control module if I’m not mistaken. If that got wet that would make all the sense in the world on why there would be issues.

I believe all the MMI stuff is in the driver’s side rear. I was under the impression that the comfort control module was in the passenger side floor. I haven’t looked at a parts diagram yet tho.

I took the four torx screws out and cleaned the circuit board in that mmi part… someone spilt coffee on mine and it was all crusty. I cleaned it with rubbing alcohol and haven’t had a problem since.

I wonder if Vag Com would see a code on the entertainment unit? That could help figure out what components were damaged.

That makes sense, but who would put electronics under the carpet?? Is there a video for removing the carpet? Never done that before…

I know some years have the Bluetooth in the passenger front and the body control is in the driver front. If the body control is wet this can happen as well. The comfort might be bad as well or compromised

Mixofia can you pull up all of these modules In vag com. That would tell you more

I only have a Carista. But this was my scan just after the flooding

OBD2 - pending:
P0492 - Secondary Air Injection System Insufficient Flow Bank 2
P0491 - Secondary Air Injection System Insufficient Flow Bank 1
P1497
P1498

CAN network gateway:
00532 - Supply Voltage B+

Battery regulator:
02277 - Static (Quiescent) current stage 6
02272 - Static (Quiescent) current stage 1
02273 - Static (Quiescent) current stage 2
02276 - Static (Quiescent) current stage 5
02256 - Quiescent current

Parking sensors:
00446 - Function Limitation due to Under-Voltage

Ignition authorization:
00191 - Passenger’s Door Handle Touch Sensor (G416)
00532 - Supply Voltage B+
00446 - Function Limitation due to Under-Voltage
00956 - Key 2

Central electronics:
00446 - Function Limitation due to Under-Voltage
00532 - Supply Voltage B+

Central electronics 2:
00446 - Function Limitation due to Under-Voltage

Body/convenience system:
02743 - Right brake / turn signal lamp

Heater & air conditioning:
00797 - Sunlight Photo Sensor (G107)
00532 - Supply Voltage B+
00797 - Sunlight Photo Sensor (G107)

Driver’s seat:
01336 - Data Bus for Comfort System
00532 - Supply Voltage B+

Front passenger’s door:
00532 - Supply Voltage B+
00920 - Heated Outside Mirror (Z4/Z5)

Back-up camera:
00446 - Function Limitation due to Under-Voltage

Instrument cluster:
00532 - Supply Voltage B+

ABS:
00493 - ESP-Sensor Unit (G419)
01826 - Sensor for Steering Angle (G85), Voltage Supply Terminal 30
00473 - Control Module for Electric Park- / Hand Brake (J540)

Headlight aiming:
00446 - Function Limitation due to Under-Voltage
00532 - Supply Voltage B+
02233 - Left Headlight Power Output Stage (J667)
02234 - Right Headlight Power Output Stage (J668)

Engine:
P0491 - Secondary Air Injection System (Bank-1)
P1411 - Secondary Air Injection System; Bank 2, Insufficient Flow
P1923 - Please Check DTC Memory of ECU Number 2

Engine (2):
P1573 - Left Eng. Mount Solenoid Valve, Open circuit
P1497 - Secondary air injection system bank 3, flow faulty
P1498 - Secondary air injection system bank 4, flow faulty

Adaptive cruise control:
01316 - ABS Control Module
01317 - Control Module in Instrument Cluster (J285)

Parking brake:
01316 - ABS Control Module
02443 - Control head
00532 - Supply Voltage B+

Obtained with Carista 3.6.2 for iOS.

I don’t see anything directly but there are a lot of voltage codes. Is there a chance that there isn’t enough voltage to power it up?

Can you check batt voltage

That was a few weeks ago. The battery actually went low enough in the following days that I had to get a jump. I assumed it had to do with the water leak and all the testing to see if the MMI would magically return in the following days

After the jump and a 30 min drive the battery is been fine.

But I often got the battery regulator faults from last winter when the car was parked outside sub-zero. At the time I tested the battery current draw and it dropped below 5 mA after 20 mins to go to sleep… since I moved to the tropics, I haven’t had a problem starting until after the leak. But now I can’t check the battery status in MMI.

Hey, my radio and backup camera worked last night! But not today. It’s very random, but MMI buttons are not responsive either way. I think this is what I need to inspect: MMI 2G head unit pn 4E0035729. Can anyone confirm that this module is located under the front left/passenger carpet?

https://i.ebayimg.com/images/g/H~UAAOSwN2VZROsR/s-l1600.jpg

It seems to be $100 on eBay.

https://www.ebay.com/itm/AUDI-A6-C6-a8-D3-MULTIMEDIA-INTERFACE-MMI-MODULE-4E0035729-4F0910730D-/172735600132

That’s what I think it looks like.

I finally got around to checking it out—pulled the glove box out and lifted the carpet. Here’s a quick video:

https://youtu.be/eutCJYAPipo

It doesn’t seem like there are any electronics that under the carpet. I only see some wiring. The MMI head unit appears to be above the glove box. I can also see the MMI fiber optic pulse a red laser from the connection to the changer. So something must be working. So the current symptoms are 1) no LEDs or response from the MMI controller/buttons, but 2) the screen shows the logo on startup then goes black after a few secs and 3) the backup camera and CD changer occasionally work, but mostly don’t.

Does anyone see any obvious signs that point to an MMI fix? Otherwise I’ll just try the head unit

And does anyone see the source of the leak in the video?

Did you check back under the seat or under the driver side. Usually right in the middle you will find the Bluetooth mod or certain control mods.