Left tail lamp warning on 2012 Vito w639

[peterb2428]

Hi All

So recently tail lamp left warning has appeared on the dash - all other lights working ok , have tested all connections which seem ok however only showing volts when lights on, right side is fine and shows 12 when switched on.

Any tips on what to check

 

[peterb2428]

So after more testing the cable required to make the light work shows 0 volts - if i link from other side all works but error meassage will obviously stay, idea is to run a single back to wiring at fuse box if i can identify the correct wire, does anyone hve a wiring schematic for this