Silverado Headlight Relay Location

[iCryWheniGoPoop]

Title pretty much says it all... where are they?

 

Thanks in Advance

[tbarn]

Low beams are wired direct from bcm. High beam control relay is in the underhood fuse box which are "non-serviceable Printed Circuit Board (PCB) relays and are internal to the block".

[iCryWheniGoPoop]

Ok... so non serviceable relays on Headlights but are you sure about the BCM supplying ground to a 10-15amp load. That is just not a common electrical practice because I'm sure the IO on the BCM has to be is the sub 1 amp range or the BCM would be twice the size.

 

Thanks for the help

[Spurshot]

Check the ground schematic at GM Upfitters page. Lots of grounds on the body. I'd ground to chassis before putting that high a load thru the BCM.

Edited June 29, 2015 by spurshot

[tbarn]

Allow me to rephrase it Low beams are powered by bcm directly. Rely is High beam only.

 

The headlamps may be turned ON in 3 different ways:

•When the headlamp switch is placed in the ON position, for normal operation
•When the headlamp switch is placed in the AUTO position, for automatic lamp control
•When the headlamp switch is placed in the AUTO position, with the windshield wipers ON in daylight conditions, after a 6 second delay
The BCM will also command the low beam headlamps ON during daylight conditions when the following conditions are met:

•Headlamp switch in the AUTO position
•Windshield wipers ON
•Vehicle in any gear but PARK
When the BCM commands the low beam headlamps ON, the vehicle operator will notice the interior backlighting for the instrument cluster and the various switches with backlighting control will dim to the level of brightness selected by the instrument panel dimmer switch.

The body control module (BCM) monitors three signal circuits from the headlamp switch. When the headlamp switch is in the AUTO position, all three signal circuits are open. When placed in the AUTO position, the BCM monitors inputs from the ambient light sensor to determine if headlamps are required or if daytime running lamps will be activated based on outside lighting conditions. When the headlamp switch is placed in the OFF position, the headlamp switch headlamps OFF signal circuit is grounded, indicating to the BCM that the exterior lamps should be turned OFF. With the headlamp switch in the PARK position, the headlamp switch park lamps ON signal circuit is grounded, indicating that the park lamps have been requested. When the headlamp switch is placed in the HEADLAMP position, both the headlamp switch park lamps ON signal circuit and the headlamp switch headlamps ON signal circuit are grounded. The BCM responds to the inputs by illuminating the park lamps and headlamps. When the low beam headlamps are requested, the BCM applies B+ to both low beam headlamp control circuits illuminating the low beam headlamp

 

 

Grounds to the frame near front body mount. Right and left respectivly.

Edited June 29, 2015 by tbarn

[Dan Volpe]

I have a 2014 Silverado.  I installed LED light on the low beams and it worked fine.  I decided to purchase LEDs for my high beams.  I installed the DS and it worked fine.  Installed the PS, and it wouldn't work.  Also now my PS low beam will not work,  I replaced the PS LEDs with the OEM bulbs.  Nothing works on the PS only. I checked the fuse in maybe 26 under the hood.  3 prong 10 amp.  It was not blown.   Any ideas or suggestions?

 

Regards

Dan

[Synnyztet]

2015 Sierra 1500.  Just ran into the same issue, we went to see a late movie last night, when I started to drive home I noticed it was so dark so I pulled over and sure enough, both headlights were out.  I pulled the driver side bulb and it was fine, not burned out and today I tested the plug and it was showing 6v, yet no light.

 

My first instinct was the BCM but no one had one in stock so instead of doing nothing, I figured it has 70k miles and a new set of bulbs couldn't hurt.  Once I removed the air box and got to the passenger bulb I noticed the filament was gone, burned out.  I did that one first since it's kind of a pain to get to.  So....both had voltage yet the good bulb still did not work, yet replacing the bad one made them both work.  I don't understand how that is possible but, this was exactly the case... I tested everything twice to ensure I wasn't losing my mind.

 

Perhaps the good one only had voltage without a bulb in it is the only logical thing I can think of although I don't see how that's possible either, maybe the BCM just gets confused?  It still confuses me lol.

 

Spend 60 bucks on some LED's and save yourself the trouble and headache.