Electrical/Headlight Issues After Delete

[73556085455]

Hey everyone, I’m having some weird electrical problems with my 2021 GMC 3500 Denali and hoping someone out there might have dealt with something like this before.

 

Background
I just had my truck deleted (DPF/EGR) recently. Everything ran fine at first, but right after the delete, I started getting a bunch of issues related to my headlights and turn signals.

 

What’s happening

• My left turn signal blinks super fast and stays stuck on sometimes

• My left headlight is mostly dead except for one small LED

• When I turn on the left signal, my right headlight will blink

• I’m also getting a “Service Charging System” warning

• The shop that did the delete said it was due to a bit of condensation inside the left headlight and told me to replace the whole assembly

• But I don’t buy that condensation was minimal, and the timing lines up exactly with the delete work

 

What I’ve done so far

• Visual inspection of the headlight, no heavy moisture or obvious damage

• Checked connections, nothing seemed loose or corroded

• Haven’t replaced any fuses or swapped parts yet

 

I’m not super confident it’s a headlight failure, more likely something electrical got messed with during the delete. Has anyone else had similar issues? Any ideas on what to check next?

[Another JR]

I can’t imagine the delete itself done properly causing those lighting issues, but if they disconnected things to do the work they could have caused it by not getting everything reconnected the same way. Maybe ask if they can tell you what wiring they disturbed in doing the work. If they won’t tell you, try looking in the areas they would have worked. I would especially look for loose or disconnected grounds.  

Edited April 16, 2025 by Another JR

[73556085455]

1 hour ago, Another JR said:

I can’t imagine the delete itself done properly causing those lighting issues, but if they disconnected things to do the work they could have caused it by not getting everything reconnected the same way. Maybe ask if they can tell you what wiring they disturbed in doing the work. If they won’t tell you, try looking in the areas they would have worked. I would especially look for loose or disconnected grounds.  

I took it back the day after the delete when I noticed the issue and they basically told me to kick rocks and to buy a new headlight

[newdude]

5 hours ago, 73556085455 said:

Hey everyone, I’m having some weird electrical problems with my 2021 GMC 3500 Denali and hoping someone out there might have dealt with something like this before.

 

Background
I just had my truck deleted (DPF/EGR) recently. Everything ran fine at first, but right after the delete, I started getting a bunch of issues related to my headlights and turn signals.

 

What’s happening

• My left turn signal blinks super fast and stays stuck on sometimes

• My left headlight is mostly dead except for one small LED

• When I turn on the left signal, my right headlight will blink

• I’m also getting a “Service Charging System” warning

• The shop that did the delete said it was due to a bit of condensation inside the left headlight and told me to replace the whole assembly

• But I don’t buy that condensation was minimal, and the timing lines up exactly with the delete work

 

What I’ve done so far

• Visual inspection of the headlight, no heavy moisture or obvious damage

• Checked connections, nothing seemed loose or corroded

• Haven’t replaced any fuses or swapped parts yet

 

I’m not super confident it’s a headlight failure, more likely something electrical got messed with during the delete. Has anyone else had similar issues? Any ideas on what to check next?

 

 

Any codes?  Need something to scan all the modules.  

[silveradosid]

it is probably the light, our 2021 3500 denali started having problems with the left headlight. the module that control the headlight is mounted on the bottom of the light and had water in it. there no cracks, so i dont know how the water got in. the fix is to replace the headlight. i did find later that you can buy the module separate on ebay

[carkhz316]

Its the light, and has nothing to do with the deletion of your emissions control devices.