merem

hello all,i am new on this forum and would appreciate any assisstance.
my name is david from nigeria.
i recently changed the engine 2 months ago and everything was fine.
3 weeks ago it started showing the malfunction indicator light with error code P1155.

i have not had the time to sort it out yet but i noticed from yesterday that the the vehicle goes off on its own when allowed to steam for about 20-30seconds.. when it goes off, i restart it.
a week ago i notice my radiator cap had fallen and all the water had gone out. i stopped,filled the radiator and screwed the cover tight.
so i dont know whether that overheat episode damaged a component.

but the main problem now is that i noticed a sound under the hood today and my dashboard lights and GPS display flicker like there is some power loss at exactly the same time that that hood sound comes on.
a mechanic hasnt checked it out yet.i want to have an idea of the problem before i approach a mechanic to avoid getting ripped off.
i believe its some kind of electrical issue though.
thanks for your assisstance. god bless