Transit Connect not starting

[mbkmedben]

Hello, please i need help !
i have a ford transit connect that has only 1.2v in each injector connector, when using OBD2, i have EGR valve code P0412, but i am wondering if there is any relation between these two things. My van just cranking without starting. When i bought it, it was starting but with very rough idling, i thought it was injectors, so to know which one, i tried to interchange them, and just after, i cog with exclamation mark appeared in the dashboard and van not starting anymore and low voltage in each injector.

EGR valve are doing a hissing sound when ignition is ON.

Thank you