Front fog lights come on when brake pedal is pressed

[Javier Rodriguez Tinoco]

Hi, I have a 2012 Hilux 3.0 D4D and when I press on the brake pedal, the fog lights turn on, as soon as I release the pedal, they turn off.

Has anyone had this same problem?

Thanks in advance!

 

[toyotafan]

That's a short, those types of electrical problems can be hard to track down. By fog lights, you mean the front fog lights? When you hit the brake pedal. Does this happen when the lights are on or off or both? Check your wiring under the dash to see if there's anything loose under there.

these fog lights?

 

[kennythewelder]

No, but what is going on, is you are back feeding the fog lights from the brake light wiring, or the BCM. If there is a module for trailer wiring, it could be the cause also. You will need to trace the brake wiring with a test light, back from the brake light switch ( under the dash board) to the BCM and find the fog light wiring at the BCM also if it goes there. If not, then you have a shorted out fog light wire against the brakelight wiring. All of this can be traced down with a test light.

 

[toyotafan]

or you've got a friend playing a joke on you.

 

[Javier Rodriguez Tinoco]

That's a short, those types of electrical problems can be hard to track down. By fog lights, you mean the front fog lights? When you hit the brake pedal. Does this happen when the lights are on or off or both? Check your wiring under the dash to see if there's anything loose under there.

these fog lights?

Hi, yes exactly those little fog lights on the pic right above the wheels.
I was driving today to work and noticed the dash light was on as if I had turned on the lights, so my reflex was to turn them off, but I noticed they were already off, so I turned them on and noticed the dash light was a bit brighter as soon as I turned them on. after some testing, I noticed it was due to me pressing the brake pedal and also noticed one of my brake bulbs is bad, so I'll have to replace it, do you think that bad bulb could be the culprit?

 

[Javier Rodriguez Tinoco]

No, but what is going on, is you are back feeding the fog lights from the brake light wiring, or the BCM. If there is a module for trailer wiring, it could be the cause also. You will need to trace the brake wiring with a test light, back from the brake light switch ( under the dash board) to the BCM and find the fog light wiring at the BCM also if it goes there. If not, then you have a shorted out fog light wire against the brakelight wiring. All of this can be traced down with a test light.

Hey,

I dont have a trailer wiring, or any accessory using extra wiring.
I do have a broken bulb on my right brake light, but not sure if that could be the problem, I will replace it today and check again.

 

[toyotafan]

Hi, yes exactly those little fog lights on the pic right above the wheels.
I was driving today to work and noticed the dash light was on as if I had turned on the lights, so my reflex was to turn them off, but I noticed they were already off, so I turned them on and noticed the dash light was a bit brighter as soon as I turned them on. after some testing, I noticed it was due to me pressing the brake pedal and also noticed one of my brake bulbs is bad, so I'll have to replace it, do you think that bad bulb could be the culprit?

There are some safety things that manufacturers do to help let you know that a brake lamp has gone out. I wonder if this is one of them. Replace the bulb and report back if the issue has gone away.

 

[rickc5]

IMHO, definitely a wiring problem. If you can't/don't want to mess with it, it might get expensive to have a shop try & find the problem. Has the truck ever been in a serious wreck? I only ask because many times the body shop(s) will simply hook up wires to just about anything so they can claim "it's fixed!"

 

[Javier Rodriguez Tinoco]

Update: I opened the lights and removed one bulb from my brake lights and stepped on my brake pedal, and the issue did not come up. Put the bulb in the socket again and removed the bulb from the other side, same thing, issue was gone. So I swapped the bulbs, the old ones seemed ok, side by side with the new ones they seemed exactly the same, but I replaced them none the less and now everything works perfectly.

Maybe the contacts inside the bulb were screwed up.

 

[toyotafan]

Update: I opened the lights and removed one bulb from my brake lights and stepped on my brake pedal, and the issue did not come up. Put the bulb in the socket again and removed the bulb from the other side, same thing, issue was gone. So I swapped the bulbs, the old ones seemed ok, side by side with the new ones they seemed exactly the same, but I replaced them none the less and now everything works perfectly.

Maybe the contacts inside the bulb were screwed up.

That's really odd. I did a search for this and came up with nothing so not really sure where to go from here, just watch it and see if it repeats.

 

[rickc5]

Agree--that's VERY strange. Just goes to show that you never know WTF is going on with the wiring in old trucks. BUT, a 2012 isn't that old? Very strange indeed.

 

[tibadoe]

Glad you got the issue sorted out. I can't explain that one .

 

[BuffaloBill]

That's a short, those types of electrical problems can be hard to track down. By fog lights, you mean the front fog lights? When you hit the brake pedal. Does this happen when the lights are on or off or both? Check your wiring under the dash to see if there's anything loose under there.

these fog lights?

No such thing as rear fog lights!

 

[toyotafan]

No such thing as rear fog lights!

Rear fog lights are actually a thing. Just brighter red lights.

 

[rickc5]

Rear fog lights are actually a thing. Just brighter red lights.

Yes they are. At one time, add-on rear fog lights were very popular in Europe. Usually one centered light that was a very bright red, but sometimes a pair of them. For some reason they never became popular in the US. But then Europe had/has much more fog than we do, and Europeans pay MUCH more attention to driving too, while we just get multi-car crashes when the fog gets thick.