What would make check engine light come back on a week after fuel pump replaced? on 2005 Chevrolet Uplander

Mechanic ran diagnostic and concluded check engine light was caused by faulty fuel pump and sensor, replaced and after a week the light has come back on.

Asked by for the 2005 Chevrolet Uplander
there is no code for the fuel pump. there is one for circuit issue but not the pump. a code never identifies a bad part, just a failed system.

get it re checked and correctly diaged.