obd 2 port shows no fault codes but trip display does???
 

hi all i am new here this is only my 2nd post, i have a 2003 chrysler grand voyager 2.5 crd, its a nightmare to start on a cold morning so thought glow plug issue got electrical tester out and no current to glow plugs checked relay and one of the pins is discoloured and part of relay is melted slightly, new one on order be here friday, i ate humble pie and ordered one through the main dealer as could not find a pattern part £36 ouch for a relay,
just out of curiosity i decided to plug my fault code reader in to see if there was a fault code to show this, came up with dtc 0.
i then tried it in car by turning key on,off,on,off,on and it came up with p0620
generator control circuit. for us people that only speak english it is altenator control circuit. i had my altenator replaced some time ago as it was u/s can i clear this from the memory some how?
i dont have any engine check lights on etc, i have tried to erase codes with my scan tool with no luck, any help would be great thanks