No cable to replace, it is electic, sender is on the rear end cover, check for water and debris in the conector first, some times the wires just corrode away and need to be replaced. If you had the service light reset right befor the speedo stopped working (hope for this) remove the instrument head and reconnect the wire that goes to the speedo. Your speedo may have just died and you will need to either have fixed by a shop that does just that or a replacement can be had from the want ads or ebay or junk yards.