[David_2404]

My car (e90 320d SE) has seatbelt light glowing and warning chime whilst driving alone with my seatbelt on.

Think it's 'cos valet boys got passengers seat too wet affecting occupancy sensor. Warnings vanish if I plug passengers seatbelt in.

So, I have silenced the chime through ncs expert, but cannot figure how to reset warning light on dash.

Any advice appreciated - I have INPA etc, but not an expert.

[bfleming]

It's a defective seat mat, which is very common on every BMW for the last 20 years. You can code this out in the Airbag module.
The code lines you're looking for to disable the seat occupancy sensor both contain "oc3" (set to nicht_aktiv). The line description will be something like "Beifahrer...".
Before coding, unplug the occupancy sensor mat under the seat, and after coding remove all error codes. They should stay off!
It disables the occupancy sensor mat, but the airbag system still assumes there is someone sitting in the seat, and an airbag will deploy.