An Open-Circuit Test On MMI 2G MOST Bus and VCDS Read Out Results

Audi MMI 2G & 3G MOST bus is very simple but yet very hard to diagnose which components connected to the bus is faulty due to the serial optical connections. If the system is not thoroughly tested and diagnosed, many good parts can be replaced in the process. This is a simple test just show that an open circuit caused the system looked bad and VCDS report shows many non related failures.

If the head unit 4E0 035 729 failed, I would check all the Polarized capacitors for short, burnt (bulging top).

I could see drop down voltage regulator (LP3965ES) or Maxim1634EAI that would be a failure if there’s a surge in power.
Since there’s NO video display DS90CR285MTD – LVDS controller must not have power –

Head Unit 4E0 035 729 Circuit Board

MMI 2G Diagram

VCDS Output Results on an Open MOST bus AMI circuit     VCDS output results on working MOST bus

2 Replies to “An Open-Circuit Test On MMI 2G MOST Bus and VCDS Read Out Results”

  1. My name is Adeniji Femi , from Nigeria, Africa. I have a problem with my Audi q7. V8 engine, 2007 model. Anytime I reve d engine of d car, it does not give me d optimum performance.
    The scan carried out by my Mech here tell me DAT, dir is a problem with cylinder 7, and DAT I need to buy complete chain and rails. Pls advice. On what u think, and how do I source for d said part online.

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