Automatic Headlights Mod

[gsteirer]

I was truly disappointed when I received my new Black '05 Prius with Burgundy/Grey interior - no automatic headlights? This is a celebrated feature in my Stratosphere Mica '04 Sienna XLE Limted AWD and my Garnet Fire '03 Infiniti G35 Sedan! Both with HID headlamps. When will we see a mod for this...perhaps CoastalTech is working on this? Has anyone tried this type of modification?

If I had my druthers and more patience, all my cars would be a Prius!

Thanks - Greg

[engunneer]

By auto-headlights, do you mean DRL? or that the headlights come on autmatically at night/in dim light?

They currently do shut themselves off when you leave the car and turn back on when you start it. That is auto enough for me.

[Tideland Prius]

That's just Auto-Off. Automatic headlights have full on and off functions and automatic dimming of the instrument panel depending on lighting conditions. If I have my headlights on in the day, the dash will not dim until I go into a tunnel or underground lot.

[gsteirer]

Exactly! Not DRL. For those of you that have not gotten to experience the wonderful benefits of automatic headlights, it is similar to automatic air conditioning...as in driving from California to New York and maintaining a perfect 72 degrees of cabin temperature...and thus you will never again touch the headlight switch from dawn to dusk and back. I have to have this feature to be completely happy with my new Prius!!!

We must make this happen!

- Greg

[naterprius]

Okay, guys, this looks doable. I've checked all the pinouts on the headlight computer; it looks like we'll need the following:

-the headlight switch (stalk) out of a Canadian Prius
-the light sensor (goes on dash next to climate control light sensor)
-some wiring and some pins

I suspect that the spiral cable (which allows wiring to go through a turning steering wheel) already has all of the circuitry. Without this, it would be impossible to do this properly.

This is likely about $300 in parts for a "maybe". I'm trying to figure out how to simulate the switches and sensor at the headlight computer to see if this can be done; this one might be late this summer at the rate I'm going on mods these days.

Nate

[DanMan32]

Yes Nate, I thought that too. However, how would you enable it in the body ECU? It doesn't appear as an option in the THHT according to Rick.

If we CAN get it to work though, then we may be able to get the fogs to work as DRL.

And as for the stalk, I would just as well add a switch on the dash.

Now if we can get the specs on the light sensor, then we could build our own. Then maybe the DRL/Auto option will show up in the THHT.

But, as supposedly was done for the alarm, there may be an undocumented disabling wire.

[naterprius]

Dan, the EWD clearly shows the circuit for the Auto headlights. My guess is the Body ECU doesn't run different software for US and Canada.

Grounding pin 18 of connector B5 (19 pin) may provide automatic lights; on the other hand it may throw code B1244. (Malfunction in Light Control Sensor).

The diagnostic manual only mentions that the sensor emits a signal waveform; no mention of whether the body ECU turns the lights on or off when it sees this waveform nor whether the trigger is when the waveform is absent or below/ above a threshold.

On a side note, it looks like DRL's could be totally controlled using pin 2 of connector B7 (26 pin) to ground a relay which goes to either the high beams (on non-HID models) or the fog lights (on HID models).

This would of course require activation in the body ECU with the handheld tester.

Nate

[gsteirer]

What is more practical...building your own circuit or modifying the ECU? It seems to me that a circuit could be built to utilize the dimmer on the dash and to intercept the headlamp switch on the steering column. Using any old photoelectric sensor, we could build a circuit to trip the headlamps and dim the dash and it would stay pretty clean. Although not as elegant as the ECU mod. I just have no ammunition in that area because I have yet to locate schematics. What do you think?

- Greg

[gsteirer]

Also, is it difficult to get parts...like the sensor from a Canadian Prius? How would one go about procuring this part, or could we use one from another Toyota vehicle?

- Greg

[vincent1449p]

If you are looking for schematics, you may like to check this out.

Automatic headlight switch

Nate, I wonder pin 18 of connector B5 has any similarities to the pin 2 (TRIG) of the 555 Timer in the above circuit?

Vincent