Depending on the scanner if it was one that will read diesel code could be a reason. Did the scanner link up in other words did it just tell you there was no codes or it didn't work at all. If it didn't work the fuse to the cigarette lighter powers up the OBDII port. Or you don't have any codes stored. All your battery connections are good and you have at least 10.5 volts to the pcm while cranking? If you do its possible its a cps.