George Trudeau

Happy Sunday, AudiWorld!

I have a display screen problem that I think I figured out the next steps for. However, I want to check with all of you first because I don't want to throw a $150 eBay part at a problem that it may or may not fix without getting some opinions. Plus, I believe getting to it is going to be a major PAIN (uggh).

The problem: Screen goes grey, sometimes with lines, sometimes fuzzy (Images below). The longer the car sits, the more likely it is that it will work again. Right now it sits days at a time since I got my wife a new car, so it almost always works when I start it. After I shut it off and turn the car back on again while running errands, the screen goes grey and I just turn it off. Everything connecting to MMI will work though. It's literally just the screen. I have memorize how many clicks everything is and it still works perfect- I just can't see the settings on the screen. I thought about replacing the MMI control board, but, it would seem to me that the buttoms and **** wouldn't be working if that was the problem.

So, that leaves me with the hypothesis that the display screen itself needs replacing. I also see a harness for sale in 40 different iterations on eBay so it makes me wonder if that's a common issue. Thoughts?

It may be important to know that this car has several other issues right now. It throws a lot of fault codes, but nothing specific to this problem (that I can tell anyhow). "Optical Bus Diagnostics" toll returns no errors, and everything 'OK'. So it seems the electrical end of it is fine but the HW is bad.

THOUGHTS?? Thanks in advance!!

tigerwillow1

Not a big help here, I realize. The problem is either the screen, the electronics driving the screen, or the interconnections. Skimming the service manual, I think it says the connection between the controller and display is on the can bus through m.y. 2009, and on the most bus after that. Before replacing parts, I'd at least remove and re-seat the connectors on the controller and display modules.

George Trudeau

No, this is actually QUITE helpful, thanks! Great points actually, and, the CAN/MOST differentiation will be quite useful.

Does anyone know WHERE the controller is physically located? Or, know where I can find schematics that outline this?

Thanks!
George

tigerwillow1

Here's some info for my left hand drive '08. Again, maybe helpful, maybe not. There was a module in my way when I dug down to one of the hvac flap vent motors. To get to the motor I was after, the first step is to pull the glove box. Working toward the center of the car, there's an MMI module. The instructions were to disconnect and pull it out but I was able to just unscrew its mounting bolts and push it out of the way. I do remember it had a most bus and other c0nnectors, so maybe that's the module you're looking for. The service manual says it's either Front Information Display Control Module J523, or Information Electronics Control Module 1, J794. Maybe it depends on which MMI system is in the car.