On some trucks heated line is of two pices, short and long, so before u order any part - check hose heater resistance. Lines have connectors of different colors and parts gues can identify hose by connector color.
SCR dosing valve loss of prime - usually low DEF level ore clogged with cristals
empty DEF tank, fill it with five gallons of water and let truck idle for a half of hour. Drain water and fill it with DEF. Usually removes all crystals