Watch the modules take turns transmitting and the waveform draw in. Open the wire, then move the scope across the break.
How to use it: with the wire normal, both lines mirror around 2.5 V. Hit Open the wire, then watch the probed segment — CAN-H stays clean, but CAN-L jumps the wrong way only when the module across the break transmits. Move the scope to the other segment and the trigger flips to the other module.