High beams stuck on

Another symptom of this issue for me, is that with the headlights on the off position, the headlight indicator on the dash will sometimes be dimly lit.

I just finished replacing the headlight switch and that hasn't resolved the problem. Next step is the body control unit, which is part of the fuse block under the driver's side knee bolster. Dig, dig, dig...

 

Swapped the switch and the fuse block with no major changes in the issue.

Back to the drawing board...

 

@BadDNA sounds like something is getting wet and shorting wires. Start looking at the wiring. There may be some chaffing of the harness going on somewhere.

 

Yeah, that's my next step, it's just incredibly detailed and time consuming. Not looking forward to it.

 

You really need to look at the schematic and do your testing from there. Basically, the headlight switch tells the BCM what to do, the BCM turns the 2 relays on, and the relays send power to the headlights. If the relays are turning on, there’s no point in looking at the wiring between the relays and the headlights. In any case, you should consider bad grounds. When there is a bad ground, power can backfeed in all kinds of strange ways from totally unrelated circuits.

 

I'll add that add a fuses installed backwards will do strange things too.
I used one for a DC per outlet. The fuse I pulled was for the wipers. That fuse blew and I didn't know it until a charger was plugged in that power outlet I installed. Then the wipers turned on during a bright sunny day... wtAf...lol that was good for a laugh..

 

So...here we are again. The problem resolved itself in January before I could find the cause, now it's back today after some heavy rain the past couple of days. Hopefully this time I can get into it more before it goes away on its own.


I'm guessing something near the firewall bulkhead got nicked at some point, probably when I was fishing wires through it. Could there be a harder spot to try and find a nick in a wire...

 

Spray the area down with WD-40. See if you can narrow it down a bit.
You could be looking under the dash... Let's hope you don't have to.

 

So, I didn't have time to work on this over the weekend, but I got a few minutes at lunch today and I've narrowed it way down, now I just have to get in there, find the damage and repair it. I removed the trim around the drivers feet and started wiggling the harness around some. The headlight indicator was on the whole time with the switch and ignition both off. When I grabbed the harness at the firewall and gave it a little wiggle, I was able to get the indicator to go off and then come back. Sucks that I'm going to have to dig way in there to find and fix the problem, but at least now I think I have found it, after several years of dealing with this crap. I'll probably take advantage of this to tear the whole dash off and clean up all the years of small projects that have added a pile of spaghetti to the wiring under there.

 

Found it! Now to clean up the corrosion, slap a little dielectric grease in there and put it all back together.

 

Well...fuck.

 

What was the final resolution here? I'm having same issue but my vehicle spent a night in the ocean so it could be any number of connections.

 

OMG. I wish you well with that nightmare on steroids.

 

I daily drive it.

 

Just wait until the real corrosion starts.

How deep was it submerged and for how long in salt water?

What connections you ask. All of them that were remotely near the salt water or any water.

 

The roof was 2 feet under as long as the high tide lasted. This happened 5 years ago. Every ecu and harness connection was cleaned and reassembled 5 years ago. This is the only current electrical gremlin I am having. That's why I asked the guy who posted a pic of corrosion which connector it was. I appreciate the warnings and all, but this truck belonged to my ride or die homie, and he died so it's not going anywhere and I'll deal with whatever comes my way.

 

https://www.tacomaworld.com/media/kendos-tacoma.403550/

That's the truck and that's me sitting in the passenger seat and my wife in back. Kenny (kendo) was my homie over 25 years, I'm not letting a little salt water kill his truck.

 

Holy hot damn. Mind sharing the story that goes along with the truck being in 8 feet of ocean!? If you havent already

 

Living next to salt water I can say I have never seen anything but a limited parts car after a submersion.

 

It wasn't any old salt water. The Sea of Cortez is extra salty!