Hi Ameriks and
to the forum.
Error 2 on the BAC-601 smart display indicates a throttle fault. Replacing the throttle with another working one would be the easiest way to confirm if it's just a failed throttle.
It might be worth trying it with the throttle connected but with the brake connectors disconnected and see if you still have the same problem.
If the error disappears, try plugging in the brake connectors one at a time to see which one is causing the problem.
If the throttle cable has been trapped, chaffed or strained, there could be a break somewhere inside the wires or even a poor soldered connection on the throttle's Hall Sensor.
If the fault occurred during a ride in wet weather, perhaps some water has found its way into either the throttle unit or the 5 pin throttle connector or even the main 10 pin connector, as this might also be able to cause the error 2. Visualy check that all connectors are still nice and dry and also make sure that no pins have been accidentally bent on any of the connectors during your testing.
The +5V output from the controller that powers the Throttle's Hall Sensor can sometimes fail completely
(or simply become too low) so you might want to take a look at
this post to see how to check the +5V output from the controller.
I realise that you've already tried another controller, but if there was a problem with the bike's wiring it may have affected the +5V supply.
Alan