[efunroom]

"The functions of the Steering Column Switch Cluster (SZL) are ... Detecting the controls in the multifunction steering wheel (MFL)" (pg 44 - E90 GENERAL VEHICLE ELECTRICAL II.pdf)

-- MFL packets was produced by SZL


"The Junction Box Electronics Control Module (JBE) serves as: Gateway Module for vehicle Bus System (provides a pass-through function for F-CAN)" (pg 10 - E90 GENERAL VEHICLE ELECTRICAL.pdf)

-- JBE does not forward the F-CAN packets directly, only pass-through


"The DSC control module is connected via the F-CAN to the SZL and serves as the gateway for the SZL, allowing data from the SZL to be distributed to the other control modules." (pg 44 - E90 GENERAL VEHICLE ELECTRICAL II.pdf)

-- DSC is the gateway between F-CAN and PT-CAN


Then, how Radio(RAD2) get the MFL commands? A possible way is :
MFL Push --> SZL --> F-CAN --> DSC --> PT-CAN --> JBE --> K-CAN --> RAD2

I noticed that there is a direct link between PT-CAN and FRM. What is for? No BUS type info in the legend