Prius Prime door light wire

The instructions that came with my OEM door sills FOR MY 2017 Prime tapped the footwell light under the steering column.
https://attachments.priuschat.com/attachment-files/2017/02/120826_MY16_Prius_Illuminated_Door_Sills-DIO_IssA.pdf

 

^ i can confirm. this is how my dealer installed door sill lights are.

 

The European manual for the same accessory tells you the wire colors at the left and right footwell lights.

The Electrical Wiring Diagram and the diagram of the Footwell Light Circuit in the Repair Manual (available by subscription to techinfo.toyota.com) show that unswitched power (pink or gray) comes from the 7.5 A DOME fuse, but not through the DOME CUT relay. Ground (green or white) is connected to the FSPT terminal on the Main Body ECU, where it is switched by a transistor.

 

The door courtesy lights are 12-volt incandescent lamps. They are connected to the 7.5 A DOME circuit, switched by the DOME CUT relay, by red wires on terminals 1 and 2 of No. 22 Junction Connector (N96), and to ground by beige wires on terminal 1 (anode) of two diodes, N18 (left) and N19 (right).

The cathode connections (terminal 2) of these diodes are pink (left) and red (right) wires, connected through a junction connector (left) or splice (right) to ground via the courtesy light switch assemblies; to the FLCY and FRCY input terminals of the Main Body ECU; and for the left side only, to the CTY input terminal of the Skid Control ECU.

There will be a small voltage drop across the diodes, of course, which are in the circuit so the courtesy light switch assemblies can both control the lamps and provide a door open/closed input to the ECUs.

 

For the footwell lights, the Terminals of ECU chart in the Lighting (Int) section of the Repair Manual says the voltage between terminals 3A-36 or 3A-37 of the Instrument Panel Junction Block Assembly (both connected to the FSPT terminal of the Main Body ECU) and body ground should be “11 to 14 V” with the footwell lights off, and “Below 2.2 V” with the footwell lights at full brightness.

The door courtesy lights are different, since there is no transistor in the circuit, just the diode.

 

The positive terminals of the footwell lights are always connected to the auxiliary battery, at 11 to 14 volts, relative to body ground. The negative terminals are connected to the FSPT terminal of the Main Body ECU.

To turn the lights off, the Main Body ECU keeps its FSPT terminal at 11 to 14 volts, relative to body ground, so there is essentially no difference in voltage between the positive and negative terminals of the lights, and negligible current flows through them. To turn the lights on at full brightness, the Main Body ECU pulls its FSPT terminal down to 2.2 volts or less, relative to body ground, so there is a voltage difference of 11.8 to 8.8 volts across the lights, current flows, and the lights illuminate.

If you set the interior lights to full brightness, and then measure the voltage between the two terminals of one of the footwell light connectors, what do you find?

 

A little late but did you get this sorted out? My footwell lights are dim and now the lightup doorsill won't come on.