2013 High beams not working normally

OK folks, fun times ahead..... I'm an aircraft electrician for the USAF so I know how to read a schematic and use a meter. My problem is the only schematics that I can find don't show me exactly what the stalk switch is doing. Anyhow, on to the story.

Replaced the head lights a couple of years back without issue. Fast forward a bit and the headlights would get stuck in High regardless of where the stalk switch was (Here's one problem, I had voltage on both the hi and low legs to the head lights). Hit some washboard once and they dropped back into Low until I pushed the stalk forward again. The Hi indicator only illuminates when the switch is held aft and I can visibly see a change in the lights.

Today, I put a meter on the headlight connectors and the Low gets 12 vdc in Low and when held aft the highs get 12vdc (lows change to zero). Nothing on the high side when the stalk is pushed forward and the lows stay at 12vdc. Pulled out the fuse box to inspect the wiring and everything looks good.

From the schematic, it looks like the Hi side and the intermittent HI (holding aft) use the same wiring to trip the Dim relay. Replaced the stalk switch today and no change. I just find it odd that I have two switches now that have the same problem.

The fog lights never go off even when the Hi beam indicator is lit.

I'm going to see if I can bypass the switch with jumpers to test but these schematics are unlike any I've ever read.

 

Remove the DIM relay and open it up, check to see if it's corroded or arced.

 

Replaced twice already. No arcing/corrosion anywhere along the lines that I can see and if it was bad, the headlights would never go High when the stalk switch is pulled.

 

Played around with the headlights last night.

Everything looked good in Low until I pressed the stalk forward, No change to high. Pulled the stalk aft and the lights go High with the High indicator illuminating (and here's the fun part), drop the stalk back to Low and the High beams stay on without the High indicator on.

Pulled the High fuses and the Highs stay on (while the stalk is in Low). Push the stalk forward and nothing, pull the stalk aft and the lights go out entirely. Seems I have two problems.

 

Sounds like you need the schematic to start with.

 

You didn't read my first post did you?

 

@6 gearT444E is a wizard with this electrical stuff and has schematics out the ass and can read them well. Maybe he can chime in.

 

Thanks! I'm hoping he has the break out for the stalk switch because the ones I have don't show any internals.

 

All the combination switch does is provide a ground.
The Body ECU intercepts the combination switch circuits to negate the ground when they are left ON when the vehicle is turned OFF. If they are cycled OFF n ON while vehicle is off they stay ON (battery drain)
Assemble a jumper for each wire.
For LOW & HI it's one choice or the other, so don't be trying to test at same time.
So the combination switch (light stalk) has off, Tails, Tails and Low Beams. Low or High and tails, Momentary flash HI (vehicle on or off), lock Hi.

 

I just had what I believe to be the same problem on my ‘15 a couple weeks ago, could only turn the high-beams off by turning the lights off and back on, stalk stopped working. It was during a cold snap, and seems to be ok now but I’m monitoring closely.

 

That's the info I needed. I didn't know how to interpret the schematic until then.

I'm going to look at the Red-Green wire coming from B5(A) into pin 11 of C11. That should be the control wire for the High lock (forward position of stalk). Hopefully, it's just a bad wire and not a bad ECU.

 

I jumpered the red/green wire out of the ECU that allows a path for ground through the stalk/combo switch. All good which means its the ECU.....

Now I have to figure out how badly I want the highs to work.

 

They’re only like $100 so I say go for it. LKQ is a very reputable used parts dealer.

 

Time for an old school foot button.

Me personally though I would replace the unit under concern that if there's one failure/issue already who knows what's wrong with it and what's going to unexpectedly die next.

 

Reference: attached Headlights.pdf, Page 2

Challenge would be getting connector point 1A5. (should be able to squeeze a meter probe in next to the wiring)

When the hi beams should be off, but are not, what voltage is measured at 1A5?
It should be >11.5V.
(presuming here Main Body ECU is operating at full range of Supply, rather than 5V)
If it is, the the Dimmer Relay contact is stuck on; swap with another relay to try again.

If point 1A5 is Low (9V to 3V) then we have enough leakage current flowing through the coil to keep the DIMMER Relay on.
This would suggest wiring is making contact to a ground, or Main Body ECU has a problem.

If it is at <3V then the Main Body ECU really does think the hi beam should be on, and is getting some input to that effect.

page 4 gives you the expectation of what the stalk switch is doing.

 

Reference: Headlights.pdf schematic
hmm I may have the wrong schematic here then because if the hi beam fuses are pulled, this interrupts the feed from the dimmer relay output to the hi beam filament.
That eliminates all other control actions prior to the fuse.

For the hi beam to stay on then, then there must be connection between the low beam and hi beam side of the bulb, and the same problem to exist on each of the headlight's connector/wiring. (or i have referenced completely the wrong schematic)
- correct model# of bulb(s)? is something i'd check, very puzzling.

 

All wiring from the firewall forward has been verified good, without shorts of any kind. I even wondered if there was "backfeed" through the bulb from a chaffed wire causing a secondary ground but I'm pretty sure that I'd have a decent electrical fire on my hands if that was the case.

I can easily audibly hear and verify by meter, the Dim relay kick over when the combo switch is pulled aft and see the high indication illuminate. No click over and no indicator when pushed forward.

Once I reinstalled plug 1L (seen here: https://www.tacomaworld.com/media/headlights.660467/ ) the lows would switch back on when the stalk was released back to Low. Highs work when pulled aft but not when locked forward. The truck has never been underwater and the wiring looked fine but I didn't have an inspection mirror to see inside the connector.

I ordered new headlights yesterday.

 

I was thinking that as well, if the ground for the headlights was bad, and finding as you note, a secondary grounding path that should not be there, but in looking at the diagram, that's not feasible, you would end up with two filaments in series, and the light output would be noticeably dim then. Also for both sides to be doing the same thing would be very rare in that case.

 

Before this afternoon, when the High flash was held aft, the lights were dimmer than they were when the stalk was in Low but they were lighting up High. I hope that makes sense.

The only way that it could happen was if the primary ground had a higher resistance than the high coil and possible secondary ground. Now if the Body ECU is screwed up, then sure it's possible. I've seen electronics do some weird shit.

Update: Never mind, I have no Highs whatsoever except for the Lows are actually Highs. We'll see what happens when the new headlights get here.

 

None of those are the Body ECU.
This is: (opened, rear view)

Rear view- buttoned up