CarPC JoyCon Exr does not require removing diode to connect both to Car audio and CarPC JoyCon Exr.
Channel Master/Slave is selectable in JoyCon Explorer.
Channel Master is to connect steering wheel control's DATA wire only to CarPC JoyCon Exr.
Channel Slave is to connect steering wheel control's DATA wire both to Car audio and CarPC JoyCon Exr.
In some case, AUX volume of car audio need to be controlled while using car pc.
When there is two steering wheel remote controls,
or when you want to use some buttons of one remote controller for car audio volume control, and the others for car pc. You try to tie DATA wires of CarPC JoyCon EX and car audio.
If clock spring have a spare channel, you can connect each left right remote controller separately. However if there is no spare channel or if you want to use some buttons of one remote controller for car audio, the only way is to tie DATA wires of CarPC JoyCon EX and car audio.
But remote controller don't work correctly for car audio when DATA wires are tied.
Because CarPC JoyCon EX was not designed to be connected with car audio.
Nevertheless, there is a way.
At this condition, car audio is AUX mode that receives only volume control signal.
If not, for example, the "Next Track" or "Previous Track" signal for car pc goes both to car pc and car audio. So car audio operates unexpectedly.
And buttons for car audio must not assigned for car pc.
If a button for car audio volume control is assigned to keyboard keys, car pc operates unexpectedly everytime the buttons are pressed.
In summary, buttons for car audio must be used for car audio volume control.
buttons for car pc must be used for car pc control.
If the diodes are removed, buttons work properly only when the car audio DATA wire is tied to CarPC JoyCon EX DATA wire.