OK.
Can you please provide the Make, Model and year of your minibus? Going to need to see the vehicle's wiring schematic for how,
exactly, your vehicle locking system is configured. "Winging" it often results in the law of unintended consequences rearing its ugly head...
.
Generally, locking systems are wired such that
all vehicle locks are fed from a
common set of relays. Basically, each lock/unlock motor is wired in parallel with all the others. Some vehicles have a "First un-lock" command that operates the driver's door
only, with subsequent commands un-locking the remainder.
If nothing else, wiring into the sliding door lock motor harness, from the driver's side door (dash?) is going to be a bit of a bear. Not saying it can't be done, but...