U1800 2002 2500HD will not start or starts then stops .

Question

truck would not start in the cold.Was already hard to start in warm weather. changed batteries and fuel filter,shows no codes other than U1800.

Answer 1

U1800  Message from FICM not received

Will not start and just show U1800 , then the fault lies with the FICM its power and ground circuits, There a common problem with code , what happens is chaff wire of the FICM  at or near the alternator which tends to rub thru.that area should be checked