Headlights - Low voltage

Hello, First post here, looking for some troubleshooting advice.

2015 Yukon XL SLT, 160k miles.

~3 months ago i installed the LED H11 from Headlight revolution, GTR brand, I didn't have any problems with them until yesterday driving i had issues with both low beams turning off during driving, when turning the headlight switch to off/parking/on/auto it would sometimes resolve, sometimes not.

Today during testing i was able to recreate the problem and noticed it only occurs with driving, ie bumps or some type of change in engine speed/eletrical system load as it does not happen when the vehicle is parked with the headlights on and engine running.

I also noticed at the headlight that was off the voltage was ~7.5VDC, when on it was ~12.5VDC (Measured at the molex connector with bulb unplugged).

Both headlights come back on with turning the vehicle off/on again.

Any thoughts on where to begin trouble shooting would be appreciated, so far it looks like it may be an issue with the body control module (?), is it possible to isolate that or troubleshoot it?

The first thing that I would do is closely inspect all of the connectors that you had to move/connect/disconnect when you installed the new lights, just to make sure that there are no bent pins or dirt on them. Then, I'd wiggle each connector with the lights on to see if the issue occurs. Personally, I doubt that it is the BCM.

Hi Joseph,

The only connector I messed with is the endpoint where it plugs into the headlight, I tried unplugging/replugging, but that still doesnt explain the low voltage I measured at the contacts of that connector, it also didnt resolve the issue.

kqsm52vyc said:

Hi Joseph,

The only connector I messed with is the endpoint where it plugs into the headlight, I tried unplugging/replugging, but that still doesnt explain the low voltage I measured at the contacts of that connector, it also didnt resolve the issue.

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POWER/GROUND/FUSE
it's most likely going to be one of those
the reason for 7.5v vs 12v is "load" if the fuse or wiring is not working properly then it cannot carry the required voltage under a load
if cycling the power fixes it temporarily, same thing, it might work for minute but then craps out.
It could always be something else......
but fuses are cheap and easy to replace. EVEN if they look ok I would replace the low beam fuse's, high beam fuse's, DRL fuse's, and any separate running light fuses.
that will cost you like $10
that's a pretty basic place to start and see if anything changes

Hey thank you for the ideas.. I changed the 2 fuses @ 121/122 labeled lt/rt HID headlight and still no dice.

I did notice it seems to turn off with bumps, and it almost seems to turn back on with RPM in park, as well as the fog lights were on when the headlights were off, but they were flickering/not consistent - It keeps point to a voltage issue for me but when i measure V at the battery/engine on its ~15V...

Any ideas where there could be a loose connection??

kqsm52vyc said:

Hey thank you for the ideas.. I changed the 2 fuses @ 121/122 labeled lt/rt HID headlight and still no dice.

I did notice it seems to turn off with bumps, and it almost seems to turn back on with RPM in park, as well as the fog lights were on when the headlights were off, but they were flickering/not consistent - It keeps point to a voltage issue for me but when i measure V at the battery/engine on its ~15V...

Any ideas where there could be a loose connection??

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Also try the other fuses I mentioned, couldn't hurt. You could also try swapping relays. Any rust where you live? If so then grounds will be next up

Where would i find the grounds?

I swapped back to regular halogen bulbs and the issue goes away, assuming its something to do with the computer thinking a headlight is out and cutting power to that circuit or something going on between the "smart" bulb and the computer.

I'm going to send this thread to headlight revolution and see if they have any advice, Thank you for your help.

Most LED headlights have cooling fans to keep them cool. You can usually hear them when they come on if the truck isn't running. Do you hear the fans? If not, those lights may be overheating and shutting down.

kqsm52vyc said:

Where would i find the grounds?

I swapped back to regular halogen bulbs and the issue goes away, assuming its something to do with the computer thinking a headlight is out and cutting power to that circuit or something going on between the "smart" bulb and the computer.

I'm going to send this thread to headlight revolution and see if they have any advice, Thank you for your help.

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if the problem goes away when you put the stock lights back in then it's pretty likely the led bulb/bulbs have developed a problem.