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)
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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
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.