Iveco 35s12 speedo fault?

I have a 54 plate Iveco 35s12 and the speedo has been faulty for a while. It used to stop working for a while then start working again but now it has stopped completely. I have checked the fuses which relate to the speedo and replaced the sender unit on the side of the gearbox but still nothing. Also the injector light stayed lit when the speedo failed and now is illuminated all the time now the speedo has stopped completely, I assume it is some way related.

ANY SUGGESTIONS???