DIY: Make 2015-2017 LS/LT headlights operate like a LTZ headlight (LED as DRL vice low beams)

[NappyBoy]

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@Tylus very well done. I actually just built pigtail harnesses that swap these circuits so the factory forward lamp harness doesn't have to be modified. That way it's plug and play and reversible.


I updated the pic with the finished harnesses (taped & wire loom like the factory harness)



Couple questions:

1. You mentioned the Y91 forward lamp harness is larger to allow for more voltage draw. However, the wire gauge sizes are similar across the suv platforms at the headlamp connectors. The only exceptions are for those with RPO 6J7 (for PPV highbeam flasher) and the Escalade DRL circuit. Both are 18AWG instead of 20AWG in those instances. What am I missing? In 2018, when GM began using the LED strip for DRLs on all Tahoes, the main harness change I see is the wire at position 6 on the headlamp connectors only being 18AWG and only describing it as the DRL Control circuit.




2. I also saw where you said the wiring diagram showed the LTZ LED strip being physically different. Can you expand on which diagram and where it shows that? I'm not seeing it.

Getting the LED strip to have the same brightness as the LTZ version is what I've been working on. What I haven't determined yet is whether the LED strip hardware is different on the LTZ or if it's the circuitry/programming on the components inside the headlamp assembly. The parts catalog I can see doesn't show anything about the LED (only HID/non-HID assembly). Like @Kpwweb mentioned, I wonder if it's a PWM control issue where bypassing it with a relay would work. Although, if that's the case, I would think Gen5DIY's $230 LED DRL harness with its relays would address it. They make a point to state the LED brightness won't change. Maybe that's all their harness does, swap the circuits and use the DRL control to activate relays to provide a constant +12v. They even give the same disclaimer on park lamp/headlamp functionality change that you noted. What are your thoughts?

The only other way I'm currently aware of to do this is with three relays. That allows the LED strip to function as DRLs and keep factory functionality with the other headlamp functions. That's the way @73Vetteman did it.

I'm happy to build the pigtail harnesses with or without the relays for those interested. I'll even do the install with the relays if you'll come to me so I can verify the LED brightness. I'm in Mobile, AL.

where can i buy these harness and how much ?

 

[bradac]

The light behavior with and without my harness makes sense. On 15-17 models, the headlamp DRLs are ran at a reduced brightness via PWM voltage.

You’ve confirmed the LED strip in the 18+ headlights is different from the older models.

When you turn your headlamps on, do the LED strips dim on the 18+ headlights?


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No, without your harness, it does not dim the LED when headlights completely on,

which is concerning as at night it’s almost blinding to look LED strip when the headlights are engaged, since it’s at max brightness. I’m wondering if there is a wiring solution for this.

When I connect the pigtail harness you provided it will only keep the LEDs dim at in all modes except off, and not max brightness. problems with this is you never get max brightness then.

I’ve attached two photos below, one during the day with remote start without the harness. One at night without the harness (not the max brightness, it’s allot worst in person, like looking directly into a headlight.)

 

[cmatt]

No, without your harness, it does not dim the LED when headlights completely on,

which is concerning as at night it’s almost blinding to look LED strip when the headlights are engaged, since it’s at max brightness. I’m wondering if there is a wiring solution for this.

When I connect the pigtail harness you provided it will only keep the LEDs dim at in all modes except off, and not max brightness. problems with this is you never get max brightness then.

I’ve attached two photos below, one during the day with remote start without the harness. One at night without the harness (not the max brightness, it’s allot worst in person, like looking directly into a headlight.)

View attachment 226340 View attachment 226341

Agreed. I can see the increased LED strip brightness being an issue for oncoming traffic.

This makes sense as the non-LTZ LED strip in 15-17 models operates in one mode as it only comes on with the park/headlamps and remote start scenarios.

We need to confirm if the strip dims with headlights on for 18+ Tahoe/Suburbans. I would expect it to.

Regarding the wiring, can you grab a pic of the wires present at your factory headlight connectors? Based on the schematics, I want to confirm if there are 7 or 8 wires present.

My concern with a relay is that it may affect the PWM voltage to the strip and not send the reduced voltage to dim the strip.


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[cmatt]

d

where can i buy these harness and how much ?

Send me an email to [email protected] and I’ll go over the details.


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[NappyBoy]

Send me an email to [email protected] and I’ll go over the details.


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just emailed you

 

[Tylus]

We need to confirm if the strip dims with headlights on for 18+ Tahoe/Suburbans. I would expect it to.

My concern with a relay is that it may affect the PWM voltage to the strip and not send the reduced voltage to dim the strip.

for 2018+ lights on 15-17 models:

the Y91 schematic on page 1 shows the LTZ models control voltage to the LED vice just straight 12v from battery in the -Y91


Maybe install the work-around harness and then put a voltage reducer (technical name lol) on the LED power feeder line? A little tweaking would find the optimal voltage to produce good DRL output without blinding traffic. Then just lock the voltage down at that value. Easiest and simple approach to minimize headaches down the road. Most LED's draw 5v or less for full output.

​

 

[bradac]

Agreed. I can see the increased LED strip brightness being an issue for oncoming traffic.

This makes sense as the non-LTZ LED strip in 15-17 models operates in one mode as it only comes on with the park/headlamps and remote start scenarios.

We need to confirm if the strip dims with headlights on for 18+ Tahoe/Suburbans. I would expect it to.

Regarding the wiring, can you grab a pic of the wires present at your factory headlight connectors? Based on the schematics, I want to confirm if there are 7 or 8 wires present.

My concern with a relay is that it may affect the PWM voltage to the strip and not send the reduced voltage to dim the strip.


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yes it does in does dim on the 2018 models, when the headlight/parking light is engaged, I can confirm this. its only full brightness when the vehicle is in drive and its daytime. let me grab a picture

EDIT

Looks like 7 pins on 2018 and up standard headlight assembly

 

[cmatt]

just emailed you

Thanks. I just responded.


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[cmatt]

yes it does in does dim on the 2018 models, when the headlight/parking light is engaged, I can confirm this. its only full brightness when the vehicle is in drive and its daytime. let me grab a picture

EDIT

Looks like 7 pins on 2018 and up standard headlight assembly

View attachment 226377

Thanks for the pic of the headlight plug. Just to confirm, this is the 2018+ headlight?

The missing pin is position 8. It’s a headlamp bulb outage circuit. It may only be on Yukons/Escalades. My Yukon has all 8 circuits.



How many wires do you have at the harness side of the headlamp plug?


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[cmatt]

I’d like for someone to check the Forward Lamp harness connector at the X50A fuse block. It’s circled in yellow. You’ll have to remove the top of the fuse block to access it.



I want to see if there are wires landed in the H2 & H6 positions. If we can power them correctly, perhaps that can address the brightness on the 18+ LED strip.






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