When I did my footwells I tapped into the orange/black wire from the dome light.
This wire is on the same circuit as the dome light.
This allows the footwells to have the same function as the dome light.
CAUTION - IF YOU USE THE WIRE BEFORE THE GLOBE, IE. BETWEEN THE SWITCH AND THE GLOBE, THIS IS AN (-) EARTH WIRE.
IF YOU USE THE WIRE AFTER THE GLOBE, THIS IS (+) POSITIVE.
Alternatively and it may be easier, you could tap into the yellow/blue earth wire at the ignition lock lamp,
or the orange/black positive wire
Which ever wire you use, the other wire must be either a constant positive or negative which ever the case may be.
All the door switches run to the BCM and not directly to the dome light, so wiring the footwells here, would only switch the lights on when then the doors are
open and off when they are closed. It wouldn't give any auto function or allow the lights to be controlled by the switch.
When one or more of these switches are activated, it sends an earth signal to the BCM which in turn sends an earth signal to the dome light switch. This earth signal only operates when the switch is in the 'door' position.
If the switch is in the 'on' position, the lights are fed directly from a body earth.
Having the door switches run through the BCM gives you the timed off function and the auto on/off when the remote door lock is used,
when the switch is in the 'door' position.
I've included a diagram of the circuit.
Don't take any notice of the circled circuit, as this was for someone else.
