Chevrolet Repair: Electric Fans Stay Running, chevrolet silverado, coolant temp

Question
My truck is a 05 Chevrolet silverado 1500 5.3 v8.
Recently my duel electric fans on my radiator have stayed running after turning the key off and truck sitting for a good 15min-5hrs. and they will still come on have changed relays, coolant temp sensor, and they are still coming on. Also when starting the truck they will go off. On code reader it brings up cooling fan 1 control bkr. Then when driving down rode will run fine then start missing out and smoking white smells like gas not oil it did bring up code for fuel tank pressure sensor but this all happened all the sudden within a day.

                         Thanks Keith        
    P.S. any help would be appreciated

Answer
You said you changed the relays you do know that this truck has three relays for the fans.Are both fans running? Are they running at high or low speed?
There has also been a problem with a corroded ground on the right cylinder head causing missfires and other problems you may want to check it attaches either to the front or to the rear of the right side cylinder head