There's a different di2 plug that can be installed in individual parts for error checking but if that's working off the bike it's most likely wrong installation. Download the Shimano manual and follow the instructions it by the letter, it's usually pretty good.
There's a different di2 plug that can be installed in individual parts for error checking but if that's working off the bike it's most likely wrong installation. Download the Shimano manual and follow the instructions it by the letter, it's usually pretty good.