My car came with a rcd500 radio which i swapped out for an aftermarket one. Last week this broke but i sold the rcd500 but i had my old rcd300 from my previous car in the loft so ive put that in for a while but im getting a fault code saying its incorrectly coded and that all the speakers have an open circuit. I didnt have this problem before even with the aftermarket stereo. It all works fine except its really bassy and its doing my head in. Where will i find the correct coding? thanks