Earl says, “ I recently had a minor crash and fell on the drive side of my bike. After the crash my Di2 rear derailleur seems to have stopped working. Any ideas as to what could have happened?”
Without being able to see the bike I can only assume that the derailleur has gone into crash or protection mode. This is a feature that not to many Di2 users are familiar with and even if they’ve heard about it, aren’t really sure what it does. When the derailleur is impacted hard enough, the motor in the rear derailleur will disengage from the cage and prevent the system from shifting. This is a safeguard to protect the derailleur from further damage in a crash. If you find yourself in a situation where this has happened, don’t panic, there’s an easy fix. You simply need to put the system into crash recovery mode and reset the rear derailleur.
First, make sure your derailleur hanger isn’t damaged, because if it is bent badly, the derailleur may over shift into the spokes on your rear wheel, which may create even more problems. Enter crash recovery mode by holding down the button on your junction box for 5 or more seconds until you see the red light start to flash. Make sure you are simultaneously spinning the cranks, because once the recovery mode is activated the derailleur should shift itself through all the gears on the rear cassette. The derailleur will cycle through all the gears and re-connect the motor to the cage to restore shifting capabilities.
There is nothing you have to do to get the system out of crash or protection mode. Once the derailleur stops moving it automatically takes itself out of that mode and goes back to normal. Finally, be sure to realign the rear derailleur hanger back to normal if necessary.