On my '08 210 RT Popular, the cable leaves the isolator, and like yours exits the engine compartment and enters the frame headed towards the rear of the vehicle. On the passenger side and forward of the rear tire, the cable exits the frame and enters a junction box with leads from the batteries, inverter/charger, and the Onan (for starting the genny). This junction box (remove the cover) is your next test point. See pics attached.
Threaded Mode
