So, I have a 2011 Toyota 4Runner Trail Edition and my fog lights won't turn on. I tested the bulbs with alligator clips from the battery and they turned on so they're good. Then, I checked the bulb sockets with a multimeter to see if there's any power coming through the wires and the passenger side has power and ground but the driver side has nothing. I also checked the fuse with the multimeter and there's power on both sides while it's plugged in so it's good.

Now I'm confused..Why isn't the passenger side lighting up if it's got power? My next step would be to check the relay but supposedly it's contained within the driver side junction box assembly and I don't think you can take that apart??? Is there a way to test the relay then? Should I just replace the entire junction box assembly?

Here is the junction box assembly link to buy from a dealer:
2010-2019 Toyota 4Runner Junction Block 82730-35410 | LaGrange Toyota

Here are actual pictures of the junction box assembly on eBay:
2013 TOYOTA 4RUNNER CABIN FUSE BOX OEM PN: 82730-35410 | eBay

I'm also attaching a diagram and schematics. Please let me know what you think. Any help would be greatly appreciated.

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Basics first:

- Fuses all checked and good?

- Headlights on?

The part that stumps me is that you say you have power at the sockets. If you have power there, you should have lights - unless you have polarity sensitive LED bulbs in backwards.

Yes, headlights are on..lol. No LEDs, regular halogen. I checked the fuse with the multimeter and there's power on both sides while it's plugged in so it's good.

Well, I checked the sockets again and it looks like I made a mistake. The passenger side has power and ground but the driver side has nothing. Sorry about the confusion. I'll edit my post above. But why isn't the passenger side lighting up if it's got power?

You might have a ground problem instead of a power problem on the one side.

As for the other side, I'd start tracing back and checking for power as you go.

So, now I'm extra confused but I think I know what I should do.

This got very confusing very quickly because this has been playing tricks on me and making me second guess myself. Here is a quick list of events:

1st Check: I believe both sides had power but can't remember for sure.
2nd Check: Passenger side had power but driver side did not.
3rd Check: Driver side had power but passenger side did not.
4th Check: Passenger side had power but driver side did not.

On the 4th check, I squeezed the prongs of the multimeter past the rubber on the back of the socket to test if the wires themselves had power. Passenger side had power but driver side did not.

Also, I clipped alligator clips to the terminals of the bulb and to one end of the prongs of the multimeter (the female side). Then I stuck the other end of the prongs of the multimeter (the male side) into the terminals of the socket that had power. But, the bulb did not light up so maybe there's not enough current?

My best guess at this point would be replacing the relay which I guess means replacing the entire driver side junction box assembly? What do you think?

I hate diagnosing weird electrical problems over the internet. It's usually hard enough when I can actually lay my hands on the vehicle.

That said, you still didn't test for a good ground on the side where you had power. Add a temporary ground. The reason I keep coming back to this is because a wise Service Manger at the marina I used to work at once told me, "All weird electrical problems are a bad ground." And he was almost always right. Let's get the one side where you have power working first.

Ok. I'll tackle that part tomorrow and let you know. Thanks for all of your help so far.

On second thought, I knew I wouldn't be able to sleep tonight if I didn't try this last thing.

So......

I tried adding a temporary ground on BOTH sides in TWO different ways just to make sure. The passenger side had power this time and the driver side did not.
NEITHER BULB LIT UP. ☹️

Now what?

Check at the plug instead of the socket.

I'm sorry, I guess I was using the wrong terminology. When I was saying sockets before I actually meant plugs. I was testing the plugs the entire time. Any other ideas?

Also, the relay does make a noticably loud clicking noise when I turn the switch on. Some websites say that means it's bad and others say that means nothing or that means it's working so I just thought I'd mention it just in case it means anything in this case.

So if you have power - and now ground - at the plug, do you have it making it all the way to the socket? You need a complete circuit. Tracking down electrical problems is all about tracing and verifying power from one end to the other.

Well, I would assume the sockets are fine because when I said I hooked up the bulbs directly to the battery and they lit up I actually never removed the bulbs from the sockets. I just put alligator clips on the prongs of the sockets and hooked them up to the battery...

Never assume anything with electricity. You have to test each part of the circuit as well as each connection. Living up here in the rust belt, I've seen sockets and / or bulbs literally rust out and the connection fail.

Well, I would say that's possible but highly unlikely because the sockets came brand new attached to the bulbs from the auto parts store a couple weeks ago..

More info could be helpful. You say it’s a 2011. And now you are trying to get new fog lights to work.
Did you buy the 4Runner used?
Did the fogs used to work but now they just crapped out?
Did the fogs ever work since you had the vehicle?
Are the replacement fogs OEM?