It sounds as though you might be expecting the mirror dip to be automatic, but it's not quite. With reverse selected and the passenger side mirror selected at the joystick switch, you have to briefly pull the joystick back when the mirror will dip 7 degrees. A further pull will dip it by another 7. Changing out of reverse will trigger the mirror to return to normal. Does that work?
It's quite difficult - well for me anyway! - to be sure of which module is doing what! The mirrors are powered from the driver's and passenger door modules, but they also get 'information' from the BPM, using SCP (Standard Corporate Protocol) and CAN (Controller Area Network), via the Instrument Cluster - principally vehicle speed and Reverse selection. So you could well be right in thinking that a BPM update is required to pass on the 'Reverse selected' info to the door module. But it could also be that the BPM is doing the right thing but the door module doesn't 'understand' and needs upgrading.(All relevant wiring diagrams show the Instrument Cluster putting 'Reverse' into the CAN when dealing with mirror movement) Although JTIS mentions that the Serial Data Link is used for the programming of certain control modules, it doesn't say anymore! To be pessimistic, both modules possibly require re programming - or replacing!I'm not aware of any DIY module reprogramming experience!
It's quite difficult - well for me anyway! - to be sure of which module is doing what! The mirrors are powered from the driver's and passenger door modules, but they also get 'information' from the BPM, using SCP (Standard Corporate Protocol) and CAN (Controller Area Network), via the Instrument Cluster - principally vehicle speed and Reverse selection. So you could well be right in thinking that a BPM update is required to pass on the 'Reverse selected' info to the door module. But it could also be that the BPM is doing the right thing but the door module doesn't 'understand' and needs upgrading.(All relevant wiring diagrams show the Instrument Cluster putting 'Reverse' into the CAN when dealing with mirror movement) Although JTIS mentions that the Serial Data Link is used for the programming of certain control modules, it doesn't say anymore! To be pessimistic, both modules possibly require re programming - or replacing!I'm not aware of any DIY module reprogramming experience!