2000 yukon denali lights flickering even when off

[Haroldbates77]

I have a 2000 yykon denali,new battery,alternator,light switch. When you shut the vehicle off and exit with keys,the headlights and tail lamps will sometimes flicker or illuminate. Can hear something like a relay clicking under the dash. Sometimes its all of them and sometimes just park lamps. Advise please.