2004 4.8iS 4x4 light issue (the saga continues)

[BimmerE38E53]

So....I posted previously about my 4x4 light issue. It came on the same time as the SLS Inactive warning. Replaced the EHC and recoded all good there now and been for about 3 months. However the 4x4 light has remained on.

I have put a new gear inside the transfer case actuator. No luck. Replaced the Yaw (acceleration sensor) today. No luck. Below is the pic of the error I'm getting, but I'm not having luck running down the issue.

I also have a random idle fluctuation sitting at a red light. Not enough that the tach moves but I do feel it in the steering wheel. Just a slight up and down. Could my 4x4 light be related to a voltage regulator issue? If so how do I check?

Below is a picture of the error I'm getting.