2016 SLT lights in 14/15 SLT/All Terrain almost done

abominable z71 · April 12, 2017

I bought the headlights brand new and was sent a replacement when I thought it was the housing was bad and causing the flickering DRL. Both driverside housings I had flicker so I have ruled out the housings as bad. I also switched the harnesses sides and the driver side drl still flickers with the turn signal on until truck warms up. The first harness I had did have a loose ground wire on the harnesses plug and once I pushed it back into the plug everything worked fine for 5 days. I thought after I got a new harness there wouldn't be any more issue but I received 2 replacement harnesses from zmnypit but now have the flickering drl until truck is warmed up then it works fine.

I checked both driver side and passenger side grounds on the frame behind bumper. I ground off all rust and wax coating and reattached. When I reattached

the grounds to the frame I got a little spark on the passenger side frame but not on the driverside. I am pretty sure it is a weak or loose ground. The ground that goes to the frame behind the bumper from the headlight wire harness has not cuts I can see and is tight in the trucks plug. Could the pin inside the plug from the truck be bad and when it heats up expands and works again? I was also trying to find if another ground exists for the headlight wire harness somewhere else. Anyone have a wire diagram for the headlight wire harness? I am OCD and want to track it down. Last resort I will tap another ground wire into the harness.

That ground wire is for the entire head assy. If you had an issue on that wire you would have problems on all lights, Park/Turn/DRL/Low beam/High beam. inside of the head assy is a junction where all the grounds come together and exit the head light via pin 1. Pin is connect to the original delphi 280 connector by the adapter harness you got from Vann. From the original connector on pin a the ground wire runs down to the frame location. it sounds like you have a problem with power jumping across from the turn signal to the DRL wire. They share a wiring harness from the fuse block down to the x110 connector. Other wise the DRL and turn signal are different harnesses out of the BCM to fuse block. I have attached a wiring diagram I made while researching and building my harnesses. Not sure if it'll help much.

HEADLIGHT WIRE DIAGRAM LEFT.pdf

pgamboa · April 12, 2017

That ground wire is for the entire head assy. If you had an issue on that wire you would have problems on all lights, Park/Turn/DRL/Low beam/High beam. inside of the head assy is a junction where all the grounds come together and exit the head light via pin 1. Pin is connect to the original delphi 280 connector by the adapter harness you got from Vann. From the original connector on pin a the ground wire runs down to the frame location. it sounds like you have a problem with power jumping across from the turn signal to the DRL wire. They share a wiring harness from the fuse block down to the x110 connector. Other wise the DRL and turn signal are different harnesses out of the BCM to fuse block. I have attached a wiring diagram I made while researching and building my harnesses. Not sure if it'll help much.

HEADLIGHT WIRE DIAGRAM LEFT.pdf

I noticed the Run/Crank Voltage circuit not used in this diagram. Not to go off subject, but do you know what Run Crank is used for? I noticed this on 16/17 Silverado Lights and not being present on 14/15 lights.

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Edited April 12, 2017 by pgamboa

Payton34 · April 12, 2017

That ground wire is for the entire head assy. If you had an issue on that wire you would have problems on all lights, Park/Turn/DRL/Low beam/High beam. inside of the head assy is a junction where all the grounds come together and exit the head light via pin 1. Pin is connect to the original delphi 280 connector by the adapter harness you got from Vann. From the original connector on pin a the ground wire runs down to the frame location. it sounds like you have a problem with power jumping across from the turn signal to the DRL wire. They share a wiring harness from the fuse block down to the x110 connector. Other wise the DRL and turn signal are different harnesses out of the BCM to fuse block. I have attached a wiring diagram I made while researching and building my harnesses. Not sure if it'll help much.

HEADLIGHT WIRE DIAGRAM LEFT.pdf

This makes sense what is happening once the turn signal illuminates the drl goes off for a second then back on. It slike when the turn signal goes on it is taking power from the drl. The weird thing is it happens every morning when the truck is cold and after driving 5-15 min it functions normal. It has never gone more than 10-15 minutes of the flickering. I was thinking if there is a relay maybe it is sticking until it heats up? I just disconnected plug again and used electrical cleaner and made sure there was nothing in the plug pins blew compressed air and applied dielectric grease and reconnected. I though the plug maybe wasn't fully connected and power was jumping pins but then it would continue to flicker even after the truck is warmed up. Whatever is going on it has to be temperature related

zmnypit · April 12, 2017

I noticed the Run/Crank Voltage circuit not used in this diagram. Not to go off subject, but do you know what Run Crank is used for? I noticed this on 16/17 Silverado Lights and not being present on 14/15 lights.

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On the 16-17 X110 Light duty pin out GM has it listed as a vt/gy wire. In all of my harnesses I use it. The only one I dont use is the bulb outage signal wire.

abominable z71 · April 12, 2017

I noticed the Run/Crank Voltage circuit not used in this diagram. Not to go off subject, but do you know what Run Crank is used for? I noticed this on 16/17 Silverado Lights and not being present on 14/15 lights.

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I can't find anywhere what it's used for. I originally put a wire in my harness to connect it. I then tapped a run1/ign source from inside the cab and ran it to the headlight just for testing purposes. Long story short the headlights didn't behave any differently with it connected or not so i'm not sure what it's there for, I don't believe it does anything. While looking at different T4L headlights on ebay there were a few pictures posted of the male connector on the back of the headlight. And some of them only had 6 or 7 pins instead of all 8, and the pins that were missing were the bulb out and run1/ign pins. The diagrams for the 2016 only show this wire on the pinouts for the headlights and the fuse block connector as circuit 3139 but it never shows up in any of the wiring diagrams including the pinouts for the LED controllers. now the 2017 upfitters diagrams are out and it's shown in the headlight diagram both lights are fed from the same 10 amp fuse in the underhood block and it shows circuit 3139 going into the LED controllers but only on the LED headlights in the sierra not the silverado and not into the HID version of either.

abominable z71 · April 12, 2017

On the 16-17 X110 Light duty pin out GM has it listed as a vt/gy wire. In all of my harnesses I use it. The only one I dont use is the bulb outage signal wire.

What do you connect it to? There isn't a run1/ign signal coming down on the 14/15 harness.

This makes sense what is happening once the turn signal illuminates the drl goes off for a second then back on. It slike when the turn signal goes on it is taking power from the drl. The weird thing is it happens every morning when the truck is cold and after driving 5-15 min it functions normal. It has never gone more than 10-15 minutes of the flickering. I was thinking if there is a relay maybe it is sticking until it heats up? I just disconnected plug again and used electrical cleaner and made sure there was nothing in the plug pins blew compressed air and applied dielectric grease and reconnected. I though the plug maybe wasn't fully connected and power was jumping pins but then it would continue to flicker even after the truck is warmed up. Whatever is going on it has to be temperature related

Do you have a multimeter?

Payton34 · April 12, 2017

I dont have multi meter but could get one.

I was just looking up part#s and GM has a few differnt parts for the LED left hand side headlight a couple parts show discontinued. Maybe they changed the pins on the housing? I am going to try reach down and take pics of pins

https://www.gmpartsonline.net/auto-parts/2016/gmc/sierra-1500/slt-trim/6-2l-v8-gas-engine/electrical-cat/headlamp-components-scat

Payton34 · April 12, 2017

I just emailed GEN5 to see if they know of a pin design change from 2016 to 2017 headlamp parts.

abominable z71 · April 12, 2017

I dont have multi meter but could get one.

I was just looking up part#s and GM has a few differnt parts for the LED left hand side headlight a couple parts show discontinued. Maybe they changed the pins on the housing? I am going to try reach down and take pics of pins

https://www.gmpartsonline.net/auto-parts/2016/gmc/sierra-1500/slt-trim/6-2l-v8-gas-engine/electrical-cat/headlamp-components-scat

The 17 upfitter shows the same pin out as the 16. If the pins had changed the head light wouldn't function properly right from the get go. I'd get a multimeter and check the resistance from the X50a connector to the x110 connector, and from the turn signal wire to the drl. Resistance connector to connector on the DRL wire should be a fraction of an ohm the only resistance should be due to the length of the wire and from the turn to the DRL should show open circuit or something along those lines depending on the multimeter you use.

pgamboa · April 12, 2017

I'm helping a local member with his 14/15 to 16/17 Silverado - Front End conversion. I've omitted the Run/Crank and Bulb Detection circuits. We'll see what happens. Just wondering if this has anything do with y'alls issue.

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zmnypit · April 12, 2017

What do you connect it to? There isn't a run1/ign signal coming down on the 14/15 harness.

Do you have a multimeter?

On the 14-15 its pin E and H. Both are just Park lamp supple voltage. Like I mentioned tho leaving it out makes no difference as long as one of them is used. I tested both ways on my repin of my truck and nothing changed. I just add them mostly out of habit and you never know what kind of scenario you may run across if I left it out. Actually had a guy using that wire for something to do with a snowplow.

Edited April 12, 2017 by zmnypit

Payton34 · April 12, 2017

I really have no idea anymore its only the driver side with this issue. I am going to look through the factory harness for any cut insulation on the turn signal and drl wires but the fact everything works ok after about 10 minutes of driving baffles me. If there was a short with wires it should be happening all the time.

Payton34 · April 12, 2017

I have been looking through upfitter guide to see if one of the relays in the fuse block X50A controls turn signal or DRL. I used to have a HID kit with the stock headlights and the relay on the HID harness would stick sometimes and I had to replace a couple times. This is the only explanation I can think of that would make the DRL flicker only when truck is cold. Anyone now if a relay exists under hood or in the instrument panel fuse blocks?

2SSRS · April 12, 2017

Sounds like it may be an issue with the controller module. Gm gives them 2 different part numbers K166L and K166R. These are the heat sink looking things on the back of the light. Here's one thing I discovered while installing mine expanding on what Vann found while testing his. Without a minimum of a 4700 uF capacitor on the low beam the light functioned fine while the truck was off and being powered strictly by the 12v DC battery, once the truck was started the light would flicker after about 5 seconds then come back on after about a minute and work fine from that point until the truck was shut off and restarted. The problem is with the alternator making ac current and rectifying back to DC, the power just isn't clean enough until the truck has run for a bit and the cap smooths it out to prevent this. While I never saw an issue with the DRL's this might be the case. Perhaps putting a 4700 uF cap on the DRL would prevent this it might not need to be this large for the DRL maybe a 2200 would work but a 4700 should do it? Although my money would be on the K166L controller as the issue. you can find them on ebay.

Thats not whats going on, GM uses a PMW on all there lighting, if you put it on a scope you will see this ---^---^---^----^----^ from 14V UP TO 18V, that is why you need a cap, but use ones with a 4700 MF ant 25V and up.

And we do have the same harness that you guys are sealing, right now we only have them marked as for the HD but they will work.