I installed the 545t Nite Lite system on my Prius V because I hate not having auto headlights on one of my vehicles(especially when I have auto headlights on my 4runner). I followed the step by step process from a previous post from hawkmoon77. Pictures are located underneath on my replies. photo 1: shows how I connected violet wire from 545t kit to wiper switch input wire (pin4 of Connector L48). photo 2 shows where I connected the black wire from 545t kit to chassis ground photo 3 shows where I connected the red and yellow wires from 545t kit to an Ignition + 12 volt source. Note: It turns out that pin 2 of connector L48 is a source for an Ignition +12 volts. I tested the wire with my volt meter, I placed the negative cable from my volt meter to ground and the positive cable from my volt meter to pin 2 of connector L48. I only got a reading of +12 volts when I had the Prius in "ready" mode. When Prius was off, no volts were present from pin 2 of connector L48. Therefore, you don't need to fish out the power outlet wire from center console which is much harder to do). Here is Hawkmoon77's write up. First off, I am not a mechanic nor am I qualified in any way to perform auto work. Below is not my advice, but rather a detailed history of what I did. Please use caution with this or any modification, and please do not in any way rely on my information, but rather do your own diligence and proceed at your own risk. Ok, with that understood, I'll start the detailed history of what I did... PART I - The automatic headlight module 1. Buy the Directed Electronics 545T Nite-Lite System - I bought mine for 35 bucks including shipping. There is a big range of price on these, I've seen $30 to $80 Just look around and buy from a reputable dealer. This module has been around for a long time. I have used it in my 2002 Prius for 7 years and it always worked flawlessly. Pictures of this module, and it's parts can be found in many places on the internet. 2. Prep the module for installation - a. I only needed one of the two relays. Both relay sockets are connected to the main module with a 3-wire plug. I Removed the relay in the socket with the red and green wires (i didn't want unnecessary clicks and power consumtion). The unused wires can be trimmed and / or removed. the extra socket can be removed by sliding off of the other socket and trimming wires. I opted to do that for ease of installation. b. the main wire harness contains a lot of wires that will not be used. I trimmed the unused wires as close as I could to the plug, and made sure that no stray wires created a short. I then put a dab of hot glue across the end of the plug where I cut the wires for added reliability. The wires breakdown is as follows: Violet (12v+Wipers) - To auto turn on the lights when the windsheild wipers are used. This is optional. If you like this feature, keep this wire. If you will not use this feature, it can be removed. I wanted this feature so I kept the wire. Green (12v-Wipers) - I removed this as it is not used. Yellow (12V+ ignition) - This wire is needed. Blue/White (12V- Aux channel) - Normally used to connect to the alarm system to operate headlights from remote. This feature is not available for the Prius security system as no auxillary channels are available. As such, I removed it. Black (12V - Ground Wire) - This wire is used, so I kept it. Orange (12V- Ground when Armed) - This is used to flash your headlights when you arm the car. Theoretically it should be possible to implement this feature, but I did not think it was worth the trouble. As such, I removed the wire. Red (12V constant power) - This wire is used, so I kept it. c. Note that the module containes a toggle switch. This feature is used to implement daytime running light mode. I did not think this was necessary since if you want daytime running lights, and are willing to turn on a toggle switch, it seems as though you could just put the headlights on using the headlight switch. As such, I did not use it. d. The remaining piece in the kit is the light sensor. Nothing special about this, just keep it handy. 3. Apply foam tape - Foam tape is not included in the kit, but I got some thin adhesive foam (3M brand) tape and applied to the underside of the main module, the relay socket, and the relay. The purpose of this is to prevent any rattle or buzz when these parts are installed. Well, that's the end of Part I. In Part II, I'll provide details as to how I began the disassembly of the car. In Part III, I'll discuss how I hooked everything up. PART II - Disassembling the insides of your brand new car 1. Safety First! I removed the negative battery terminal of my accessory battery following the instructions in the owner's manual. (Note that disconnecting this terminal will reset some settings in the car and may require the reinitialization of some features. The manual is very detailed in this regard, so review it so you understand what will happen when you disconnect the battery terminal.) 2. Remove the bottom portion of the steering wheel column cover. a. Adjust the steering wheel so it is in the upmost position. b. Push the right side of the lower housing in to disengage the two claws. c. Do the same for the left side. d. At the bottom of the hole for the tilt lever, closest to the passenger side, there is a snap that can be removed with your finger and some downward pressure. e. Rotate the steering wheel so that the top of the wheel is facing the drivers side door. You will see a small rectangular hole in the front of the lower housing. Find something that fits in it and push inward to release the claw. f. Spin the wheel 180 degrees clockwise and repeat step "e" for the right side. g. The cover will come right off exposing the headlight wire harness and the wiper wire harness. Remove these harnesses for ease of access by pushing on the little release lever on the plug. Note that the wiper harness is actually two seperate plugs taped together. 3. Remove the inner door sill panel - this is the plastic trim on the floor as you enter in the vehicle, just behind the weather stripping, between the weather stripping and the seat. There are a few clips holding it in. Just pop it out and toward the seat. 4. Remove the driver's side cowl cover. this is the plastic piece that is just to the left of the brake pedal, on the floor. Alternatively, it is the roundy, curvy, plastic piece that touches your left foot when it is on the floor footrest. a. Remove the plastic retaining nut. It will probably be hand tight. b. Pull the cover away from the body to remove (mostly toward the passanger seat, but also lift it toward the driver's seat just enough to clear the screw where you removed the nut). The two blue clips may stay stuck in the body. If they do, just pull them out with pliers and snap/slide them back into the cover before reinstalling. 5. Remove the lower instrument panel finish panel assembly - this is the plastic piece that has the controls for the side mirrors on it, as well as the 4 slots for the switches (one of which is the control for the dimmer of the inerior lights). a. Remove the screw at the bottom closest to the door. It will be exposed when you removed the piece in step 4. b. There are 6 claws holding it in. Just carefully pull it out. No real trick or angle. I started with the bottomm and when those claws were released, i pulled it back toward the seat. c. Remove the hood lock cable. While looking up at the white plastic behind the latch (with the back of your head comfortably against the floor of the footwell), you'll see a clip centered in it. You will have to disegage that clip (by pulling it outward) and then slide the whole assembly back (in the direction away from the front of the panel you are removing and toward the brake pedal. It will slide out. d. Remove the remaining wire harnesses attached to the buttons. If you make sure to depress the release clips on each wire harness plug all the way in, the plug will slide out easily. Do not force it. 6. Technically speaking, there may be more disassembly required based upon where one would decide to place the light sensor. I, for example, put it on the front center dash, behind the instrument cluster, out of sight and with unobstructed access to the sun. I would never actually recommend doing this as removal of the dash requires removing EVERYTHING - from the cup holder to the passenger air bag system, the NAV unit, glove compartment, all trim pices in the front of the dash, the front speakers, a handful of bolts, and the trim pieces over the front portholes, including the ones that expose the side curtain airbags. I only installed it there because I was taking it all out anyway as I wanted to see what was there. (I took some great pictures!) The sensor can be installed in any well lit, unobstructed place. Some locations may require additional dissasembly. While I won't give advice on where else to install it, as I can't really speak from expereince here, I would say that IF I was not planning on removing the whole dash, then I probably would have installed it on the dash, toward the windshield directly in front of the driver, and just to the right of the front driver's side speaker. In that location, it is mostly out of view of the driver, is unobstructed, and is much easier to install. I will include the steps that I would have taken had i decided to place it there, you know, for informational purposes. a. Remove the grill covering the speaker. There are 6 clips, 3 on the left and 3 on the right. Using a small screwdriver, I would have sliped it in between the left side where it meets the side wall of the dash. I would NOT have started on the dash side because of the design of the clips. Working in the front most corner of that side, I would have popped out the clip. Force is not a good idea here as you don't want to bend or break the thin grill. Be careful not to scratch the carpeted area by the porthole as it scratches VERY easily. It is not the easiest piece to lift up. It requires some patience. After that first clip or two is up, one would need only slide their finger under it to pop up the remaiing clips exposing the front speaker. (it is a sight by the way!) Be careful not to damage the delicate membrane that covers the speaker. b. From here, the sensor can be installed just to the RIGHT of the grill, toward the front of the grill, but positioned on the dash itself. There is a crease in the molded plastic of the dash at this point that would hide the tiny black wire well. You may have to gently notch or sand a small grove in the grill or dash to make room for the wire when you reinstall. This notch would need to be VERY small to accomidate the thin wire, so I wouldn't overdo it. Just enough to get everything back nice and flush. I suppose with additoinal thought, one could figure out an alternative location to put the sensor. Naturally, the alternative location may required some further dissassmbly, or who knows, perhaps none at all. Creativity is key here. That's it, the disassembly is complete. In Part III, I'll detail how to wire it up. Part III - Wiring it all up. 1. Decide how I will make the conenctions. Now that I have access to everything, wiring is pretty simple. The first decision I had to make was how to connect the wires. My options were: a. Buy plastic wire connectors that clip on. The advantage is ease of use. I've also never had one fail. The disadvantage is that the wires are all different diameters. Sizing is important since a clip that is too small could cut a larger wire, and a clip that is too large would make a poor (or worse) intermittant connection. At the very least I would need a multipack. b. Solder everything up and cover it up with electrical tape. The advantage is a long term permanent conenction. The disadvantage is a more obvious modification to the stock Prius as well as being more difficult and time consuming. I chose option (a). 2. A word on electrical tape - I would never use cheap $0.99 electrical tape. Not for anything. It has (at best) a temporary adhesion. That being said, even good quality electrical tape tends to want to unstick in extreme temps (the sort you might find in your car on a hot day). I would use it to wrap a bunch of loose wires together (pulling on the tape to give it a SLIGHT stretch as the tape is applied). But I woudl NEVER use it to cover a bare wire or solder connection. For that, heat shrink tubing of the correct diameter is essential. It slips over the xposed wire, and with the heat from a heat gun, hair dryer, or solder iron tip, will shrink and form a snug fit that can handle the vibration and heat of a car. Electrical tape is good to wrap around it, but not in place of it. 3. Below are the wires connection points I made for the main unit of the kit: Violet (12v+Wipers) - The large white wire in the harness under the wiper switch. Pin 4 of connector L48 (see picture). Yellow (12V+ ignition) - I didn't use an ignition source becuase I wanted a switch override (that is, an on-off switch for the auto headlight feature). I connected this to the red wire (constant 12V+ wire below). if I didn't want a switch, I would conenct this to a 12V+ ignition wire. Black (12V - Ground Wire) - I connected this to the bare metal of the car. Used a bit of sand paper to sand a small area of the paint off the chassis under the dash, cimped on a wire connnector, and screwed it in for a good ground connection. Red (12V constant power) - This would be connected to a 12 volt constant source (like the big white wire going into the body ECU). HOWEVER, I did not do that becuase it really only needs constant power to monitor alarm activity, and I did not use that feature. As such, I connected it (with the yellow wire above) to one side of a switch. the other side of the switch was connected to a 12V+ source when the car was on. I chose the big black wire on the back of the fuses under the dash. I could have chose anything really, including the 12V power receptacle wire. 4. Lastly, i needed to connect the relay. I connected the two wires from the relay to pins 20 and 12 of connector L47 attached to the headlight switch under the steering wheel. 5. I connected the main harness, the relay harness, and the sensor harness to the main auto-headlight ECU from the kit, and attached the kit in the space in front of the main body ECU (by the 4 switches left of the steering wheel). There is a lot of room behind that panel. That's it. Everything works and I couldn't be happier. If anyone has questions feel free to ask me anything. I'll be glad to try and help you out.