Automatic Headlights / DEI 545t install

I created a .pdf file of the information I found on automatic headlights and my installation of the DEI 545t. I've done my best to recreate it here, but have also attached the .pdf if you wish to download it.

Background:

Unfortunately it is not possible to add OEM automatic headlights to our trucks. I tried adding the sensor and changing the headlight switch and checked all options in Toyota’s TechStream software and there is no way to enable it. However, I did discover that installing the light sensor did cause the multi-information display to only dim with the lights on if it’s dark enough outside, so I’ll describe adding that sensor at the end of this document. The solution I came up with to get automatic lights working was to install the DEI 545t Nite-Lite system.

The DEI 545t is designed to be very universal and therefore, has pretty vague instructions. Installing it requires an understanding of how our headlight system works and how the DEI 545t operates. Because of its universal design, the DEI 545t has many wires we don’t need. Since the Tacoma’s headlight switch simply sends a ground signal to the BCM and the DEI 545t normally uses a ground signal to activate relays that handle high current load of the light system directly, we can eliminate all the high current wiring and simply splice the ground signals into the headlight switch harness and the DEI 545t will simply simulate the headlight switch. However, we do need a relay to disconnect the DRL wire when the headlights are triggered by the DEI 545t otherwise the BCM will turn on the DRL and the low beam headlights only, no dash lights and no tail / marker lights. Also, it is possible to have the DRL position (or the Auto position, if you replace the headlight switch) control the DEI 545t on/off via relay instead of with the provided toggle switch. I chose not to hook up the wiper input; it should be possible, but I found it unnecessary and if I did hook it up I would have wanted a delay before the headlights activated, which would have required adding a time delay relay. Also, to have them work with low and high speed would appear to require diodes to prevent feedback.

DEI 545t Installation:

I removed all unneeded wires from the DEI 545t wiring connectors. To remove, just push down on the tabs from the side and pull the wires out. The photo on the left was taken before I removed the wiper input wires; the right photo shows the 5 wires left.



The 5 remaining wires that we need are:
Red: Battery positive
Yellow: Ignition input positive
Black: Ground
Blue: Parking lights output negative
Green: Headlights output negative

Here is a wiring diagram I created; the black DRL wires are actually white:

I connected the red, black and yellow wires to the radio harness, as I felt it was the easiest, but I'm sure there are other options (I have an aftermarket head unit and related wiring. If yours is factory, you might not have an ignition wire there). I spliced the blue and green wires into the headlight switch harness on the steering column near the headlight switch plug. Access to this area is gained by removing the lower steering column cover. To remove it, you have to turn the wheel half left and remove a screw and then half right to remove the second.



The DRL wire is where it gets more complicated. The white DRL wire needs to be cut and 2 wires spliced to the switch side. One goes to the auto enable relay coil and the other goes to the DRL disconnect relay and the harness side needs to be extended to the DRL disconnect relay. This setup allows the DRL/Auto position to control the on/ off of the DEI 545t and allows the DRL wire to be disconnected when the DEI 545t triggers the headlights. The DRL disconnect relay coil also needs to be connected to the headlight wire.

Relay wiring details:





The auto enable relay and its wiring can be omitted if you don’t wish to control the DEI 545t with the factory switch. However, you will still need the DRL disconnect relay to prevent malfunction. I chose to wire the DEI 545t with this auto enable relay so that DEI 545t will operate nearly identical to the OEM system. (With the switch in the auto position, DRL in daylight and headlights at night, the DEI 545t is disabled in all other switch positions).

Toyota auto light sensor installation:

This is completely optional and will only affect the dimming of the multi-information display. To do this, you will need a few Toyota parts:



To install the light sensor, remove the passenger side dash speaker grill and replace the blank plug with the sensor. Push the 3 repair pins/wires into the sensor plug housing in the correct positions and extend the wires long enough to reach the BCM, which is located under the drivers side of the dash, and feed the wires down through the dash and connect to the auto light sensor. Then reinstall the speaker grill. At the BCM, you will need to unplug connector M6 and separate the layers to add the 3 new wires. Your new wires will need to be spliced to the BCM repair pins/wires.

 

I decided to go back and add the wiper input after all. I used a time delay relay, set at about 10 seconds, to keep the lights from being activated by the mist or wash functions. Added the purple positive wiper input wire back to the DEI 545t plug, it connects to terminal 87, blue wire from the wiper switch connects to terminal 30, green wire from the wiper switch connects to terminal 15 and with white/black wire connects to terminal 31.

Here is the updated diagram:

 

Tacomaworld, solving your first world problems.

Good work OP

 

@Pickupman2007 can you confirm, adding the Toyota light sensor and wiring it to the BCM will automatically dim the infotainment display at 'night' and automatically brighten the display into day mode during 'day' conditions? This may be worth the almost $200 in parts.

I'm trying to get used to not having automatic headlights any more. When you spend this much on a truck you think it should be standard (my '14 Camry SE had auto headlights). I can get over the headlight issue since I can leave parking or headlights on without any chime or draining the battery. The worst part is having to set the infotainment display into and out of day mode manually.

 

Unfortunately I can not, my 2016 I originally did this with came with the Entune Audio Plus system, which I had replaced with an aftermarket system. Since then I traded for a 2017 with Entune Premium but while I did transfer the auto light system I did not get the sensor off the 16 and haven't installed one on the 2017 yet. Been thinking of trying it on the 17 as that functionality was really nice with the muti-information display on the dash cluster and I was hoping maybe it would also do the infotainment display.

 

Gotcha, thanks for clarifying between the multi information display and the infotainment display. I look forward to hearing the results if you purchase another sensor for your 2017.

Another option I'm going to look into next is finding a way to keep the instrument cluster illuminated when running lights in the DRL mode. Part of the reason I run the parking lights during the day is to see the gauges when it is overcast but I have my sunglasses on for glare.

 

Where is the location of the light sensor?

 

In the corner of the right dash speaker grille. Will be the sensor or a flat blank.

 

Does this auto dim/brighten the navigation screen?

 

To my knowledge based on my original question above, I do not think this mod dims or brightens the navigation screen.

I have an idea to try to connect the guage cluster dimming to the navigation unit but haven't been able to troubleshoot it yet. At a minimum I'm going to be wiring a switch into the radio harness to act as a 'day mode' switch to keep the navigation unit bright when I run my headlights during the day. I still haven't installed this yet, but I plan to make a write up of it when I get to it.

 

Sound like a good idea. Sorry I never have gotten around to trying a sensor on my 2017.

 

No worries, that thing isnt cheap. If anyone has a pinout or wiring diagram for the Guage cluster that would help me out. I'll try to do some research soon too.

 

Question about the install:

1. I assume that you used the Toyota Tacoma OEM light sensor rather than the one provided by Directed Electronics?
2. You didn't use the toggle switch in your install? Which way would you recommend going?
3. From my research my impression about the headlight switch is that there is no need to replace it. The only differences are whether the switch says 'auto' or 'DRL'. Is that correct?

Great post and thanks for all of the info!

 

1. No you need the provided sensor for the directed box. I had tried to add the OEM system that’s why I had the Toyota sensor.

2. I added a relay in place of the toggle and tied into the headlight switch so it works like factory.

3. Correct. The 2 are electrically identical. Only difference is label.

 

Had two questions that hopefully will keep me from driving my headlight blaring truck in to a tree... No matter what I do the green wire seems to be grounded as soon as I turn on the key. I think my module is bad and not a wiring issue.

*The auto enable circuit appears to short the two pins by default and only un-short the pins when on DRL based on the drawing. I verified this is how my behaved by hooking the blue plug up to a meter. It seemed to match your behavior. According to the instructions these pins disable auto light turn on when the pins are connected. So I assume your goal here is to disable auto lights on any setting other then DRL? So you would leave the switch on DRL to enable auto lights.

*I pulled the plug with the green headlight wire. I was able to verify it drops to ground even if the plns on the blue plug where shorted together. This doesnt seem correct that this wire is grounded no matter what position my headlight switch is in. <- I guess this really isnt a question, this just seems to be wrong behavior. The only thing i can think of is there is some safety feature that prevents disabling the auto light that I cant figure out how to get around. I did try turning ignition on and off but no matter what the green was grounded at all times

*What is the purpose of the ground wire for the parking lights? I would imagine that if you ground the headlight switch that includes the headlights and the parking lights? Or are they really lit seperatly and putting the switch in headlight just grounds both those wires?

 

1. Yes, the auto lights disable in off, parking or headlight positions. So that effectively make the DRL position the Auto position.

2. Green wire from the DEI module should only be grounded when the module is activating the headlights.

Note this portion of the DEI instructions:

I may have forget to mention this is the original post but if you didn't open the DEI box and cut the red wire loop, then this may explain your issue as it would cause the green wire to ground, since our trucks already have DRL this should be disabled.

3. Yes the parking and headlights are separate circuits and turning the switch to the headlight position grounds both wires.

 

Thanks.... my DEI manual didnt have that part but this 100% sounds like my problem. Thanks so much, will cut that loop tomorrow but I bet this is it as everthing looked good at all the relays etc..

 

Has anyone here successfully executed this. I got the DEI system and im just looking at wire and black boxes. I have no idea whats going on

 

Yes.. I didnt bother with the wiper override but I did do the base setup. just do it one wire at a time. You also need to cut the red loop wire on the dei box. I used solder and shrink tubing rather then crimps. Crimps I dont mind but I have had issues with the tap connectors to I try and stay away from them.