Recently I had the engine heater warning lamp (coil symbol) turned on while driving on my 2009 VW Polo diesel. The engine started losing power when going at a speed of over 100 km/h.
After a couple of days, the lamp turned off.
My mechanic told me that the EGR valve is going bad and that it needs to be changed. After the change (an expensive one, at least for me) there were no more issues.
However, I've later been told by some friends that the changing of the valve was not necessary. Is there any truth to that?