Automatic Headlights Mod

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.

 

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

 

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.

 

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

 

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

 

Or for DRL to the fog lights how about:
Use auto headlight circuit above plus a line FROM the parking lights(to sense when there're on) combined into inverters and a AND gate to drive a relay to the FOG lights. Thus when the parking lights are off and the auto headlight circuit is off the fog lights(DRL) will be on.

 

I didn't realize the light sensor emitted a waveform. I just checked the repair manual, I am not seeing a waveform from the sensor. Where did you see it Nate?

Again, according to Rick, the DRL/Auto option doesn't display on the THHT.

 

I'm so glad to find this thread! I got my Prius on Tuesday and already miss the DRLs from my last car (and the Auto headlights from my wife's). I hope you guys have great success working this out. For the entrepreneurial types, please know there are folks like me out there who would be willing to pay for such a kit, especially if it uses factory parts from other markets (like Canada).

Thanks!
Gary

 

Nate:

Geez that sounds like a giant PITA!

I'll never again take for granted the DRL and auto headlamps on my Prius. When the salesguy gave me the "orientation tour" of my Prius, he carefully pointed out the Auto setting of the headlight switch.

I rotated it to Auto and it has never moved since.

Though if you can figure out an easy way to perform this mod, good for you.

Jay

 

It seems the biggest problem will be figuring out what the part numbers are for the pins in the Body ECU connectors. Toyota's out of date wiring harness repair manual doesn't list these connectors, so I don't know how to look up the part numbers for the pins. I keep thinking Toyota will release an updated Wiring Harness Repair Manual but don't hold your breath...

Maybe Rick can help figure this out?

The other option is to extract an adjacent pin and try to match it up with the pictures the Wiring Harness Repair Manual. (Tedious and uncertain).

Nate

 

I think your suggestion is workable. To reduce chip count, you can also use a single NOR gate.

For those without fog lights and if your headlights are non-HID, I think it is possible to reconfigure the above 555 Timer as an Astable Multivibrator. The output can be duty-cycle controlled to get your desired brightness. This way, you get DRL when it is bright and headlights fully on when it is dark.

I guess it would make this mod much easier if any owner that has the DRL module can provide some details on the waveforms at the light sensor and the headlights.

 

There is no DRL module. The body ECU handles the DRL and AUTO headlight function. The USA car has the same components as the Canada Car, except the light sensor.

Therefore, it seems all we may need is the light sensor and activation with the scan tool (although this option is reported as being absent in the scan tool menu; very strange since it's mentioned in the repair manual). Also, we will need a switch that can ground the AUTO pin on the body ECU.

Nate

 

I think I was thinking of the DRL relay, which the wiring diagram shows as a box, rather than a relay. Also, as you mentioned, the sensor shows as a box with 3 connections to body ECU. Body ECU may be looking for sensor impedance before it shows DRL/Auto features in THHT. That, or US THHT doesn't have code to implement it.

There could also be an undocumented 'enable' or 'disable' link like some have said there is for the alarm.

Anyone in Canada take some voltage readings fron the sensor, or from pins 14,15,16 on B6?

 

If you got to this thread and haven't seen the thread posted by PROBLEMCHILD, please look at that. He found an aftermarket kit from DEI called the Nite Lite System that automatically operates the headlights with a photocell. I had it installed on my 2005 prius and it is SWEET because I really missed that feature.