The first problem I had was finding a good wiring diagram for your car.
I have the early version 2000 V70 and couldn't find the list of components which
are supposed to in a fold out in the back page.
The index says central locking for the V70 is Pg 260 and in the PDF file
pg 260 is found on page 290 with 291 showing where components are.
You have to be clairvoyant to tell what 3/76 3/78 3/100 3/109 are
I guess 3/100 is the drivers door lock assembly.

Search for good wiring diagram for your car and post back
They are usually free but here's one someone wants $10 for: Maybe a division of Google? and suddenly the free ones get scarce.

https://www.tradebit.com/filedetail.php/277879325-volvo-s80-v70-late-model-s80-executive

Lots of codes are daunting. But start by fixing each problem one by one.

for instance can you lock/unlock the doors at each door?
Look carefully to define what works and what doesn't

My first Volvo a 740 sedan and every door lock motor was shot. Dunno
how all the locks went away? Maybe the car was hit by lightning?
I found good lock motors in the junk yard for $20-25 each X5

First hunt down a good wiring diagram. Post back where to find it.

Bill