This doesn’t really explain how to hook up the MOST cables…so here is what you do:
(I just want to preface that I had Logic 7 and I didn't care about chimes, I just want to be able to have software updated and to get rid of the SOS error.)
Here is what I did:
1. Purchased 2 Fiber Optic MOST cable (part #61120142318) and 2 fiber Optic cable connector (part #61136901846) from getBMWparts.com.
2. Purchased 1 Metra 71-9003 from Sonixelectronics. You do not need 70-9003 if you are are installing a Dynavin and are just moving to the trunk for the software updates and removing the SOS error.
3. Removed the Optical cables from the harness coming from the car (this is circled below on the 71-9003 harness).
4. Connected the fiber optic cables coming from the car with the 2 connectors. These will be connected to the 2 fiber optic cables that you purchased. You will have to strip the wire a bit to make sure that you get a full connection. I used a super glue product made for gluing plastic to metal. Add a bit of glue to keep the connector on the cable. I then taped it up with electrical tape.
5. You are going to have to reuse the insert from the Metra 71-9003 that is coming from the car. This is not pictured (it will be in the area circled), it is what you are going to use to plug the MOST cables into the harness.
6. Plug the MOST cables into your new harness
7. Plug the harness in the factory HU. You want to make sure that you have the cables hooked up correctly before you run them to the trunk.
8. I unplugged the harness and ran the cables to the trunk.
9. Ran a 12v to battery and ground line.
10. SOS error deleted.