Richard manning

Hi All, I've got a 320d auto 2008, the EML light has been on for couple years now. It's serviced regular, no loss of power, no smoke out the back when accelerating, still goes really well and I've had bits and pieces done over the years.The garage clears the light but then it comes back on half mile down the road. This has been the Bain of my life. I look at it every day and just want to smash the dash lol. I've been told it's possibly the EGR which is very possible. Any thoughts anybody?