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International Automotive Technicians Network
Re: Paccar MX13 P3901
Posted to HD/Fleet Forum on 2/23/2021

Hi James B.,

Each line should have a heater element near the connectors. Ohm out each of the 2 wire line heaters and see if any are open. DEF fluid has to be constantly heated. In cold weather it often takes a longer run time before the DEF reaches adequate ... Login to read more.