Ihave a 2006 a3 the epc light comes on then off when driving but the engine doe,s not go into limp mode still have full power. One garage says it,s the NOX sender and box then the audio garage says it the charcoal filter any info please . All sorted took the car too another ww audi garage and they changed a switch on the braking system , All this was done by the garage I purchased it from under warrenty but up till now no epc light on .