FIRSTLY: Ensure this is not due to a setting change on your display. Reset your display to default settings (Explained in our display tutorials)
While this error is rare, it does happen infrequently and is not unheard of. There are multiple potential causes of this issue making it very tricky to resolve, but we will be here every step of the way to resolving this issue with you.
20% - Display: The display is not reading or transmitting the data properly. Replacing the display will resolves the issue.
20% - Controller: The internal control is not correctly transmitting the speed data to the display. Replacing the controller resolves the issue. Please check and report any damaged or bent pins on the 9 pin motor cable on your chain stay.
20% - Motor: The sensors inside the internally geared motor are not correctly reading the speed because a magnet is out of place. Replacing the motor resolves the issue.
40% - Cable or Connection: A loose or disconnect cable is the most common cause of this issue.
Unfortunately there is no easy way to diagnose where the issue is coming from unless you have more than one bike in your possession. If you do have 2 bikes, this issue is easy to diagnose.
1 - Plug in the motor cable on the chainstay to the bike with the functioning speedometer. Test if that resolves the issue.
2 - Plug in the functioning display to the bike with the non-working speedometer. Test to see if that resolves the issue.
Trying both the display and the motor would eliminate those potential options and leave you with only the controller as the source of the problem.
Please reach out to firstname.lastname@example.org and let our staff know if you have the option to test components from another bike.