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International Automotive Technicians Network
Re: 2001 Cummins ISB: DTC P1688
Posted to HD/Fleet Forum on 4/21/2007

That could translate into Cummins fault code 368. Unable to reach commanded timing due to internal pump failure. Typicaly means VP44 pump needs replaced but can be caused by an inop lift pump. Verify lift pump operation and pressure. If it has an engine mounte... Login to read more.