Prius LE auto headlight retrofit

You don't need to do a retrofit; I have an LE, and although there's no auto setting on the lights, I was able to change the settings in the Multimedia to be able to turn on the headlight switch and leave it on. What will happen is when you park, the lights remain on until you open the doors, then they will turn off automatically. This way, there's no need ever to touch the headlight switch going forward.

 

Gen 5 I don't know, but some trims of gen 3 came with an actual "auto headlight" feature that would turn them on at dusk and off in light. It relied on the solar sensor that was already on the dash in all trims (used by the HVAC to adjust for comfort driving into sun or shade).

It turned out the car's body ECU already knew how to do the auto headlights, and trims without the feature simply didn't run the extra wires (from the sensor to the ECU, and from the 'auto' headlight stalk position to the ECU).

In a trim that didn't come with the feature, adding those wires was all it took to add the feature.

What I found to be the best thing about the feature is it takes over control of the dash brightness. Instead of the dash always being dim whenever the headlights are on, it's dim when the headlights are on in the dark, but brighter when headlights are on around dawn, dusk, or daytime. That part by itself was worth the price of admission.