Stranded - Shimano Di2 will only shift up or down

I am writing this post to help anyone who may need it if their Shimano Ultegra or Durace Shimano Di2 derailleur will only shift in one direction and need to fix it to get home.

This hack will not work with Shimano 105 Di2 shifters as they do not have a hood button.

TL;DR; You can remap the hood button to perform the shifting function that is not working using the Shimano e-tube app.

A couple of friends and I were doing a 77km ride around the Snowdonia mountains from Capel Curig to Stwlan Dam and back in a loop. I was riding my new Bianchi Specialissima for the first time which I absolutely love. This is the first time I have owned a bike with the Shimano Di2 electronic shifting system and I was very impressed by the capabilities and crispness of the shifting.

At around 34k while at the furthest point from the car I completed a descent and approached a climb. Trying to shift down (up the rear cassette) into lower gears I could hear the rear derailleur trying to move but not completing the shift. I could shift up though and found myself in 12 gear. Not ideal for climbing a steep climb.

I tried the following to resolve the issue without success:

• Checked the status of the battery for all the components (system battery, shifters and derailleurs)
• Checked if the derailleur needed a crash reset. This checks the tiny cam on the motor is locked into position to be able to move the mech up and down the cassette, all looked fine and engaged properly.
• I disconnected the power from the derailleur and waiting a minute, reconnecting it did not resolve the issue
• I removed the seat post and disconnected everything from the battery, reconnecting it did not resolve the issue
• I asked some cyclists passing by for help, they laughed politely and said "that why we stick to mechanical shifting mate"

After a call with the excellent team at Ron Spencer Cycles I downloaded the e-tube app, pressed the rear derailleur button for a second to enable Bluetooth (blue light starts flashing) I was then able to communicate and configure the Di2 system.

Updating the firmware

The app was able to see and communicate with all the devices, this was a positive start and I could see there was a firmware update for the system battery, both derailleurs and both shifters. Great. I started with the rear derailleur as that was having the issue, still no resolution, I then updated the battery and front derailleur to ensure they were all running the latest firmware.

I then tried to update the shifters I couldn't update the firmware, this is because they are wireless and need to be cabled to the battery to ensure the update occurs safely without a power loss. I will still in a broken state and unable to get home.

The workaround

The e-tube app allows you to customise what the shifters do, so I swapped the function of switching to lower gears with higher gears and vice versa. Boom, now shifting to higher gears wouldn't work. This meant the rear derailleur was shifting ok but there was something going on between the typical lower gear switch and the rear derailleur responding to it. Shimano Ultegra and Durace both have a third button on top of the hoods which I usually map to Garmin functions, so I tried to map this to shifting into lower gears and it worked fine.

This narrowed down that there was a problem with the switch and that the other two worked fine. I went with this configuration hack as way to complete the ride. It was a little strange shifting using the hoods and pressing the 'wrong' button for lower gears which meant I often did the wrong thing but it was fine and saved waiting hours to be picked up.

Since this happened the bike has been back into the shop for a more thorough diagnostics which confirmed a faulty shifter that was replaced the same day and I am back on my way.

I hope this helps someone get home if stranded someday.

Thanks

Special thanks to Dan Philipson and Mike Stanton for waiting in the cold with me and helping me diagnose the issue.