Only Fog Lights work, No high or Low Be

I just recently picked up an 08 Tundra 5.7 SR5 from a guy who had the truck sitting for about a year. Tried turning truck over and she wanted to but didn’t. I checked fuses for starting system and saw it was blown along with some chewed wires along side the fuse box under the hood. Replaced a 7.5 amp fuse for starting system and spliced the wires and she fired up.

Fast forward to now after tinkering with the truck to prepare her for inspection I noticed the headlights were out. Fog lights and DRL works. High beam and low beam do not work. When turning on the headlights via the headlight switch on the steering wheel, the bulb symbol comes on signifying that a bulb/fuse is out.

First instinct of course was check fuses. All fuses were fine. Checked bulbs and they looked fine but I bought new ones anyway. No dice. Took a regular automotive fuse tester light and checked headlight fuses and I am not getting power to the fuses. Checked connector side for headlights and no power with switch on or off. I took out a multimeter and checked continuity to the connectors on headlights and no continuity with the headlight switch on or off.

As far as I’m aware there is a headlight relay along with a DIM relay that I have not tried yet. I’ve tried looking up what the DIM controls with no success.

Any thoughts? Maybe mister mouse ate more than what I could see? Could my headlight switch be bad, possible to test it?

Thoughts gentlemen? Much appreciated.

 

I would think either a fuse or some critters got in there in the time it was sitting and went to town on some of the wires.

 

Welcome to the forum. Have you checked anything? Fuses? Bulbs? How to operate them?

 

Fuses and bulbs check out from what I’ve seen. I’ve tried new headlights along with new fuses. No success

 

You won't believe how complicated the headlight wiring is. Go here to download the 2008 wiring diagram: https://www.tundras.com/attachments/2008-tundra-ewd-em08h0u-pdf.544196/

Do a search for "headlight" until you get to this page. It's not really page 4. There are multiple pages for headlights.

If you're not getting power to the fuses then you'll need to work your way up from the fuses. Check if that 40A fuse is supplying power. Check if the relays are working. Check if wiring to/from relays are good. Etc...

 

Went ahead and downloaded the PDF. Very helpful. The 40A fuse you are referring to says Main next to it on the diagram. Is that part of the main fuse linkage or is a standard 40A fuse I can pull out?

 

Is this not the indicator on the dash board to show that the headlights are on? Meaning the body control module thinks they are one and is telling the cluster to light this up so you the driver know they are on.



40A Main is part of the main fuse block.
The blue HRLY wire is a ground trigger from the Body Control Module for the headlights to come on. The HEAD relay is where I would check. First do you have power on Pin#1 (Coil side). If not your 40A Main fuse is bad. Second do you get a ground trigger on Pin#2 (coil side) when the headlight switch comes on? You would check for continuity to ground, you should only get it when the headlight switch is on. If this is the case, the switch and all the wiring is good.

You just might not have power to the HEAD and DIM relay.

 

This is the man!

 

You are correct it is the indicator that lights are on, my mistake. I’m going to follow your troubleshooting and give an update when I test. Much appreciated. Loving the truck so far.

 

For additional wiring inspection pull the bottom portion of the dash panel. 12mm X2 console side with an extension to reach it. Once you pull out the bottom portion there will be additional rats nest there. Check the wire harness on the lower right side. There will be like 4 blocks of clips, make sure you push all of them in all the way just in case. Last resort would be the stalk. Should be like 2 screws to remove it, in addition to the steering column screws.

Edit: Post #17 will have a picture of what I'm talking about.
no power to under dash fuse panel | Toyota Tundra Forum (tundras.com)

 

Was just going to say, if we summon Jeff, he can help you!

Also, alldatadiy.com has an interactive schematics, you click on a wire or wires and it highlights them to the next location.

And as Jeff pointed out, one thing I've learned about Toyota is they don't run hot wires all over the place, they pull stuff to ground at a relay keeping power local to relays and running it short distances.
I'd say mouser did more than you have found.

If your headlight main relay downstream of the 40A fuse, has power, there is a pink wire (2010 schemo) supplying 4 15A fuses. Powering those fuses should help you isolate where the open is.

You'll find this quick...

GL

 

Update after many days of hunting and replacing wiring…


It was a blue HRLY(Headlight Relay) wire. Anyone else in the future with issues like this I hope you come across this post. Much appreciated to all who commented to help me narrow down the problem.



Wife thinks I should get vanity plates to honor the mouse.

 

Good job!

 

Ah yes a break in the trigger to the relay will do it. Without the ground signal here the relay never closes and the lights won’t come on.

Nice work narrowing it down and getting it fixed. Sometimes these bugs are hard to track down and get fixed.