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

[Nick Correll]

This is a cool idea in my opinion and works most of the time. I just hate that the headlights now come on when it’s remote started vs the led strip and the headlights are on while the parking lights are on. (I rarely use that but usually during Christmas looking at lights. Now it’s all or nothing. Biggest thing is when it’s remote started. Anyone ever come up with a solution for this?

never mind I read through the thread. Emailed Matt.

 

[Emotionz101]

Hello,
Has anyone heard from cmatt? Does he still make the harnesses?

 

[bholloiu]

@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)
View attachment 327166


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.

View attachment 327167


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.

Sir,
I was wondering if you still build these pigtails and if so would you be willing to sell one?

Regards,
Bobby

 

[SSpinball]

great write up, and information. exactly what I was looking for ! Thanks !

 

[rddixon]

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.


Sent from my iPad using Tapatalk

I have a 2018 Suburban Premium that had the passenger side headlight replaced and the led drl comes on but it is dim. Would your mod correct this problem? I think they put a headlight in for a LT instead of LTZ.

 

[RST Dana]

I have a 2018 Suburban Premium that had the passenger side headlight replaced and the led drl comes on but it is dim. Would your mod correct this problem? I think they put a headlight in for a LT instead of LTZ.

Matt’s mod was for the purpose of making the DDL change from the low beams to the strip. It didn’t make it brighter.

 

[MainahBob]

CMatt

I just saw your wiring harness mod. Very nice job. What did you sYou can access the drivers side without any disassembly

Passenger side is just the air box.

About as easy a “mod” as can be luckily

@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)
View attachment 327166


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.

View attachment 327167


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.

I’m still here guys and still building harnesses. I’ve been snowed under with my day job. Round two of the SBA’s Payroll Protection Program starts Monday. Hopefully it will go smoother and I’ll have more time to respond here and other avenues.

BTW I’ve developed a new DRL harness that gives LTZ like headlight behavior with exception of the LED strip brightness (the LTZ’s strip is a different part). It corrects the headlight behavior issues with the park lamps and remote start.


Sent from my iPad using Tapatalk

Hi CMatt-I have been following this string now for a while. I have a 2016 LT (that I bought new) and swapped the Halogen headlights for LEDs. since the LED is my DRL, they don't seem to last very long (2 years). I would be very interested in the connector pigtails you have made and will email you for details.