Foglights On With High Beams

WLC · April 4, 2016

All this discussion about keeping fogs on with high beams must involve people in States where there is no yearly safety inspection or States with lax lighting laws. Failure of fog lights to automatically turn off with high beams is an instant flunk in WV, VA and likely a number of other States and even the existence of aftermarket, non OEM, lighting an immediate flunk in others.....had to rip out the aftermarket fogs moving from NY to pass NJ inspection. And automatic means no manual turn off switch, pulling fuses or bulbs either to pass inspection. If the vehicle has a fog light, it has to automatically switch on and off as per State law when switching from low beams to high beams and back.

True but lawmakers have never drove a Sierra ! I put 5202 headlight bulbs in the fogs and they come on with the brights. Added aux lights also to drive at night.Original lights suck on the sierras.

darkfox1 · April 4, 2016

Take the diode out, pass inspection, put the diode in.

Once you know the pins it should take seconds.

Thomcat · April 4, 2016

True but lawmakers have never drove a Sierra ! I put 5202 headlight bulbs in the fogs and they come on with the brights. Added aux lights also to drive at night.Original lights suck on the sierras.

Or worse a '97 era Plymouth Voyager, the only vehicle I ever got rid of solely because of its crappy lights. Best were my Avalanches' with a 4 headlight setup with two of them low/high beams (like my old '60 Impala) so you could operate with 4 high beams. Of course on a pea soup foggy night on the mountain you can't use highs anyway or they'll white out the windshield.

polarys425 · April 4, 2016

All this discussion about keeping fogs on with high beams must involve people in States where there is no yearly safety inspection or States with lax lighting laws. Failure of fog lights to automatically turn off with high beams is an instant flunk in WV, VA and likely a number of other States and even the existence of aftermarket, non OEM, lighting an immediate flunk in others.....had to rip out the aftermarket fogs moving from NY to pass NJ inspection. And automatic means no manual turn off switch, pulling fuses or bulbs either to pass inspection. If the vehicle has a fog light, it has to automatically switch on and off as per State law when switching from low beams to high beams and back.

These mods are easily reversed. And if one does it like I did, I have a hidden switch that deactivates it so they function normally.

No surprise about having issues in NJ, considering they don't allow people to pump their own gas..... Being too dangerous and all.....

jaymiles007 · April 4, 2016

It sounds like the LED strip in your aftermarket light assembly has internal wiring that would need to be changed to do what you want.

Thanks man, I actually had to take out the headlight assembly today because I lost my turn signal switchback bulb into the headlight assembly when I tried taking it out. When I took the headlight out to retrieve the bulb, I spliced a couple wires and now my LED's run with my daytime lights! Thanks for the input, much appreciated..

kgr · April 27, 2016

2014 SIERRA SLT FOG LIGHTS WITH HIGH BEAM HEADLIGHTS MODIFICATION

This mod will let you use the fog lights on low beam same as factory. On and off with the fog light button.

When the fog lights are turned on while on low beam, then the high beams are either flashed or turned on and then off, the fog lights remain on when going back to low beam.

When the high beams headlights are switched on, the fog lights come on also. You cannot shut the fog lights off with the high beams on. When going back to low beam, the fog lights go off if they were off prior to switching high beams on.

Find the BCM under the dash, just to the left side of the steering column, right behind and above the OBD2 connector. It's a black box about 7" square and an inch thick. It will have 7 connectors in the lower edge of various colors.

Pull the BROWN connector loose. There is a little tab you need to squeeze inward to release it.

Look at it closely, there are tiny numbers at the corners to give you pin location reference. Use my attached connector photo and the numbers on the connector, along with the colors of the wires to locate the proper wires.

Locate pin #10 with the Brown and White striped wire. This is the Fog light signal wire for the relay.

Locate pin #18 with the Brown and Violet striped wire. This is the High Beam signal wire for its relay.

Take a 1N4004 diode and push the wire lead of the diode in along side the wires with a pair of needle nose pliers. You need to push hard to get it to slide in about 1/4" so it will stay snug. Make sure the marked end of the diode (stripe) is toward the High Beam.

You can put a piece of electrical tape over the bare diode leads or you can slip a piece of heat shrink over the diode before you install it and shrink it after pushing it in. But there's really no need as these are switched Ground leads, not power.

Put the BROWN connector back in the BCM.

YOU'RE DONE. THAT'S IT.

Hi spurshot,

Is this mod likely to work on 2015 Sierra SLT also? I'd like to be able to keep the fogs on with highs. As long as it doesn't prevent operation of the fogs with running lights or lows...

Thanks!

Tommy Naron · April 28, 2016

Hi spurshot,

Is this mod likely to work on 2015 Sierra SLT also? I'd like to be able to keep the fogs on with highs. As long as it doesn't prevent operation of the fogs with running lights or lows...

Thanks!

I have a 2015 5.3 SLT and i did the 10 to 22. my fog lights are on when the lights are on, also when you unlock the truck they are on.

i love it set this way i never have to mess with the button, its just on. check in to the 10-22.

Cgeardawg · May 5, 2016

Awesome easy to do. Wired it 10/22 works as I want it too. Great forum.

Edited May 5, 2016 by Cgeardawg

Tommy Naron · May 11, 2016

To those who have tried the 10-18 do the fog lights come on when you unlock, or lock your truck with the remote?

i have the 10-22 and they come on when i unlock, lock the truck... just curious,

im guessing they would since the lights would be on in the 10-18 settings. thanks for the info.

kgr · May 13, 2016

To those who have tried the 10-18 do the fog lights come on when you unlock, or lock your truck with the remote?

i have the 10-22 and they come on when i unlock, lock the truck... just curious,

im guessing they would since the lights would be on in the 10-18 settings. thanks for the info.

I just did this the other day...10-18 so the fogs stay on when the highs come on.

One minor downside is that even if the fogs are off, when I switch the highs on, the fogs come on. But its not really an inconvenience; I just like to be in control of everything

But to answer your question, no, nothing has changed when I remotely lock/unlock - still just the parking lights flash.

adam.busch · June 13, 2016

So this started when I got a Left Rear Turn Indicator Failure on the DIC and the dome light overhead switch not working. I took the truck in today and got it diagnosed. The diode mod, performed exactly like the steps in this forum, somehow shorted out my BCM. I can't believe that would have done it, considering several other things that BCM controls work without issue. Well, new BCM and programming repair will cost one $675 dollars, all because I forgot to take out the damn diode before going to the dealership. Anyone else have a solution for fixing the BCM outside of the dealership for cheaper? Anyone else have an issue with this modification causing things to not work on the truck? Hard life lessons.

sidenote: I also performed the footwell lights modification and I'm certain this somehow factored into the equation.

Edited June 13, 2016 by Adam P.B.

Thomcat · June 13, 2016

So this started when I got a Left Rear Turn Indicator Failure on the DIC and the dome light overhead switch not working. I took the truck in today and got it diagnosed. The diode mod, performed exactly like the steps in this forum, somehow shorted out my BCM. I can't believe that would have done it, considering several other things that BCM controls work without issue. Well, new BCM and programming repair will cost one $675 dollars, all because I forgot to take out the damn diode before going to the dealership. Anyone else have a solution for fixing the BCM outside of the dealership for cheaper? Anyone else have an issue with this modification causing things to not work on the truck? Hard life lessons.

sidenote: I also performed the footwell lights modification and I'm certain this somehow factored into the equation.

Two cents comment:

Change may have had no effect, or in conjunction with another unrelated failure controlled by the BCM may have caused a cascade effect and crapped out other controlled functions of the ECM. Luck of the draw on how it fails...diodes nearly always blow open but if it shorted out instead, and/or in conjunction with another mod may have a damaging effect. Or leaving it in while the dealer did other diagnostic testing could have caused the damage. Even if you buy a new ECM it still has to be programmed by the dealer; a used one from an identically optioned same year, same model vehicle may work without reprogramming.

Why screw around, for less than $100 you can buy the plug and play custom wiring harness using GM connectors and never have to remove anything or play with it again?

gSwift · June 14, 2016

Why screw around, for less than $100 you can buy the plug and play custom wiring harness using GM connectors and never have to remove anything or play with it again?

Have a link by chance? Thanks in advance