Where is the gen 3 Prius door switch wire (to tap-in factory alarm)

I just couldn’t find the Gen 3 (2010) Prius door switch wire under the driver side step sill.

Considering rampant Catalytic Converter theft these days, I decided to install a DIY tilt alarm with mercury gravity switches. The plan is simple, just tap in the door switch wire in the existing factory alarm system. The diagram shows it clearly.

Loosed door switch, and confirmed the wire is a thin brown one.


Opened up the step sill and found dozens of wires. There are 2 brown wires. Stripped them one by one and did tests. None is the door switch wire, as one of the brown wirings is always ground no matter if the door is closed or not, the other one never connected to ground.



Does anyone have any ideas or advice?