Hi, I’m hoping someone can give me a little advice?

I need to change the front passenger seatbelt pretentioner/buckle, the cable runs into an electrical junction box under the front passenger seat.

How do I open the box and does the new pretentioer just plug in?

Cheers
Matt

Before you touch ANYTHING disconnect the battery for 15 mins, unless you want airbags etc going off when you’re fiddling with the connections!

The manufacturers deliberately make these circuits difficult to work on because they don’t want diy’ers playing with them. Both airbags and seatbelt pretensioners contain small explosive devices which are powerful enough to cause nasty injuries if you get it wrong.
As said above, disconnecting the battery for a long time is essential, do some proper research (maybe not just a mountain bike forum!?) and don’t be surprised if you have to take it to a garage anyway to get it coded in.