First of all connect earth to the sender's plug white/brown wire, if it works the sender is gone, if not insert a needle into the white/brown wire to pin 1 of C0448/0162 and give it earth with a wire... if the lamp comes on the problem is between this plug and the sender, if not it's probably something with the lamp, blanked or faulty unless it's a wiring issue between this plug and the instrument pack but that's hard to troubleshoot if you dont know to work by the diagram.