Control Module Does Not Switch Off Light

Control Module Does Not Switch Off Light

When the MOST network is requested to sleep, the Control Display switches off the light in the MOST ring. The lack of light input is a signal to the individual control modules to switch off their light output and enter sleep mode.
If a control module does not switch off its light, all down stream control modules register the fault "A Control Module is not switching light off."


IMPORTANT: Failure of a control module to turn its light off, will cause the MOST network NOT to enter sleep mode. If the MOST network fails to sleep, the rest of the car will not be able to enter sleep mode. This will lead to battery discharge.


To diagnose:

- Read out fault memory in MOST ring order

The fault lies in the control module that precedes the module where the fault is first stored.
Always confirm the problem by first clearing the fault and performing the diagnosis a second time. If the same results occur, replace the defective control module.

Network Wakeup Unsuccessful

This fault indicates a problem with the optical transmission. An insufficient volume of light is coming through one position of the ring and may be caused by:

- Control Module is receiving no voltage
- Optical Wave Guide harness defective
- Optical Element in a control module defective (transmit or receive)
- Connector not installed correctly

A distinction must be made as to whether the fault is currently present or sporadic. For faults currently present, run the Ring Break Diagnosis Test Plan. For sporadic faults perform the Luminous Power Reduction Test Plan.

Ring Break Diagnosis Carried Out (FC E190)

Reading out the fault memory of the Control Display (Gateway) after performing the Ring Fault Diagnostic, results in a fault of Ring Fault Diagnosis Carried Out being stored. This fault memory is not a true fault memory entry, but only an output of additional information for relative node position.