Low beams and fog lights stopped working 2021 4x4 SR5

Good evening. I'm not sure when this started. Either yesterday or today. The high beams work but not the low beams and also no fog lights. I've tried the switch in the auto and manual position. The dash indicators light up. No mods to the truck or anything. We had some hot weather the last few days. I found the fuse block under the hood but I'm not sure witch one to swap out to test it. I thought someone here might be able to help. I thank you for your time.

 

Check the 15A H-LP LO fuse

 

FWIW, I am shooting blindly at the logic of the Body ECU.
But knowing that 2nd Gen fog lights will NOT come on unless the Low beams are on, I'm going with checking the Lo beam fuse first.
The Dimmer and Low Beam relay are controlled by the Body ECU. Which are operated off inputs from the headlight switch.

Keep us posted OP.

 

Thank you. I'm going to try replacing that H-LP LO fuse in the morning. Also what you said about the fogs only coming on if the low beams are working makes sense. I'll find a good parts store. Thankfully I don't have to work whiles it's dark. I wanted to go to the desert this weekend but that might have to wait.

 

Do you have a voltage meter?
I'd rather test a fuse than just replace it. (for cost savings).
I like to know, before I replace.

Also, check under the fuse box. Some times they give you extra fuses.
If not, swap the fog fuse and Lo beam fuse. They are both 15A. I seriously doubt they are both blown.

 

Okay yes. I'm assuming I would just check it for continuity, right?

 

I'd check for power on both sides of the fuse.
I like to check the fuse installed. That way I know i have power to the fuse.....

The fuse has 2 little bare spots on top of it, just for that reason.

A test light to check them is even better.

 

Oh got it. Okay.

 

Remove the Mirror Heater fuse (15A) and place in the suspected blown position (H-LP LO), test function.

 

Well I checked the fuse and it looked fine. I pulled both headlight bulbs and both fog bulbs and all four were shot. They must have all gone within hours of each other. Hard to tell though since I haven't been doing any night driving. Thank you again for your help.

 

If all 4 bulbs were blown on a 3 yo truck, I’d suspect something else is wrong.