Optical Wave Guide Communication Fault

WARNING: This page does not describe the selected car, but rather 59 other vehicles, including the 2009 BMW M5, 2009 BMW 650i, 2009 BMW 550i, 2008 BMW M5, and 2008 BMW 760Li. However, it is still accessible from the selected car via links, so may be relevant.

This fault (FC 111) indicates a problem with optical transmission. Insufficient light is being received by one of the modules in the ring. The loss of light may be caused by:

Defective optical wave guide, Harness twisted too tightly (Min. bend radius 50 mm.)
Light output or reception sensitivity of a diode is too low
Connector not installed correctly
Voltage fluctuation while powering up a control module

If the fault is stored, the system triggers a reset and starts up again. The music is switched off briefly and the display screen of the Control Display continues to operate.

To find the module responsible for the fault, the fault memory of the modules must be read in MOST ring order.

Fault lies between the module with the fault code (B) and the preceding module (A).

If the voltage has dipped below 9v, the fault may be incorrectly stored. If the voltage is low perform the following test after connecting a battery charger.

Clear the fault memory in control module B.
Lower the light output in control module A.
Read out the fault memory in the MOST ring in order.
If control module B is again the first to store the fault, it can be assumed the fault lies between control modules A and B.

Then, check control modules A and B for loose connections and check the optical wave guide for kinks. If the visual inspection is OK, the fault can be located using the OPPS tester or optionally performing the following tests.

Remove the input optical wave guide from control module B and confirm the presence of light. If light is present, install by-pass optical wave guide in place of control module A, clear fault codes in module B and perform ring break test. If MOST network operates properly, then control module A is at fault and must be replaced. If MOST network still has a fault, put module A back in the network and by-pass module B. Clear faults and again perform ring break test. If MOST network operates now problem is with control module B and it must be replaced.
If light is not present at input of module B, perform by-pass of module A as above.

The possible fault scenarios are:

Transmit diode in module A defective
Receive diode in module B defective
Optical wave guide fault between modules A and B
Software error or fault in module A or B
NOTE: AMP butt connector p/n - 1355734-1