Hey everyone! Hoping someone can help

My wife was driving her 2014 Limited home from hockey practice the other evening and she said her headlights flipped over to night mode, then flipped back to daylight mode, but since then her headlights do not work at all.
No DRLs, no low beams, no high beams unless we pull back on the stalk.
Going from Auto to headlights on has no effect, except the parking lights do turn on.

Here's what I've checked so far

• Battery voltage good.
• No CEL.
• Covering the light sensor has no effect. No dimming of instrument cluster, no lights coming on.
• Checked all fuses for continuity with multimeter; all good.
• Checked low beam bulbs direct to 12v; both good;
• Swapped low beam relay with heater relay since they're the same; no change.
• Checked relay input for 12v; 12v showing on both hot legs.
• Jumped the low beam relay with a wire and lows turn on then
• Unplugged battery for a couple of hours to reset ECU; no change.
• Pulled the stalk out and tested all pins against this page (everything is good here too): Toyota 4Runner: Headlight Dimmer Switch Circuit - Lighting System - Service Manual

At this point, I'm running out of ideas. I'm wondering if it's the light sensor somehow but not ruling out the main body ECU either.

Anyone have any ideas where I can look next?

Thanks!

Did you check to see if you're parking brake is on? Some vehicles have headlights/DRL disabled if parking brake is on, even a little. Might be the case here?

The parking brake is not engaged (this happened while she was driving), but I won't rule out a grounded parking brake wire. I'll chase it down in the schematics!

Jumping the low beam relay and then having low beams turn on may indicate a bad socket or pushed pin.

If its the emergency brake related. Had a 2013 F150 where the emergency brake lever didn't retract far enough to fully push the plunger switch.

I think it was Toyota that at least used to have a plastic knob pressed into the brake lever to push the switch. Not uncommon for that plastic piece to fall out or get off kilter.

So what's the reason for even involving lights with parking brake function?

Helps when camping. If you are car camping and get cold at night, push your emergency brake and turn the car on and lights stay off.

Do parking lights still work?

I've never heard of the parking brake thing either, but definitely worth checking for continuity across the switch when there shouldn't be, at minimum.

If you don't have the FSM already you should download that, lights start around page 5848. You've got the fault down to signal side rather than supply by jumping the relay. The new FSM wiring diagrams are so piecemeal (or does someone know where there's an overall that gives colors and all that, like they used to?) but it seems like the main body ECU provides ground across the headlight relay. So I'd check for continuity to ground from that ECU terminal, with switch on, then voltage to ground just to be safe. If neither, repeat the test at the pin for your headlight switch input at body ECU (although probably not in that order, I haven't checked the diagram though).

A Techstream dongle would probably be a big help too.

I wouldn't think that the photocell would be the problem since manually turning the lights on should override the photocell. Depending on how Toyota engineers the lighting circuit, I'd look into the headlight switch and photocell.

Parking lights do turn on

That's my next step us to start looking for grounds from the ECU for the relay. But I'm camping for a bit so this will have to wait till I get back.

I've seen a lot of references to Techstream in the FSM but do you have a good source on where I can get this? Seems like an expensive dealer software suite.

I'm not convinced on the photocell either but there doesn't seem to be a way to test it without an oscilloscope. I ordered one for $20 off ebay so it's not a big loss if that doesn't resolve it.

Only reason I an leary of the photocell is that I don't even get dash lights dimming when I cover it. Totally agree that the switch should override it but who knows what the computer is actually doing.

The switch itself tests out fine so I'm suspecting something in the main body ECU.

You can get a knockoff on Aliexpress, or you can pay several hundred for something that's less of a PITA to setup, but I forget the names of those. The genuine is thousands

The question on parking lights was for @A10MileHusker since you mentioned before that yours turn on, and he was familiar with what the parking brake did when depressed, from camping.

Sounds like the low beam relay, but you swapped that out...

Unplug one head light and test the power at the plug with head lights on. Is there power? How much power?

Steve

When you jumped the low beam relay, was there a voltage going to pin 85 when you toggle from park to headlight mode ?

If no, I would trace back why pin 85 is not going high. This needs to go high for the relay to switch. setting the stalk to light on mode should drive this.

Yes, parking lights will still work. It is designed to only keep your DRLs off but the moment the stock is switched to parking light or low beams, those will still turn on.