Wire identification help

[Kc1979#]

Hi

Can anyone please tell me what cable number W129 -  1235 does and where it goes?? 

Would it have anything to do with my fuel gauge not working and possibly creating a fault code with my fuel flow solenoid?? Saying open circuit on lexia. 

When I test ok lexis thr fuel gauge needle moves but does not drop to fully empty.

Really appreciate your help, I can't seem to find a wiring diagram to start sussing things out.


M59 berlingo 2002 2.0 DW10TD Siemens should that inor be required 

Thanks