NISSAN EGR VALVE

What Is A Egr Vavle? What Is Its Func­tion?What Hap­pens If It Is Not Re­placed?

Code P1400 Came Up I Was Told That­was The Egr Valve Needed Re­plac­ing But Thats Not What It Says When I Look It Up What Needs To Be Done?

We Have The Above Code On The Ve­hi­cle Listed Above. My First Ques­tion Deals With The Op­er­a­tion Of The Egr Sys­tem. Is The Sys­tem Ac­tive When...