2021 Kia Seltos Headlight DRL Not Working? Step-by-Step Diagnosis of a Failed LED Assembly
Introduction
If you’ve ever run into a situation where part of a headlight just doesn’t work—especially on a newer vehicle—it can be frustrating. Not only does it affect appearance, but it can also raise safety concerns and lead to inspection issues.
In this case, we’re dealing with a 2021 Kia Seltos where the upper LED ring in the right front headlamp never illuminated. The lower portion of the headlamp worked fine, which made this a perfect example of why proper automotive troubleshooting matters.
This is exactly the kind of issue that gets misdiagnosed all the time—leading to unnecessary parts replacement or wasted time chasing wiring problems that don’t exist.
Let’s walk through how to diagnose this the right way.
🔧 Recommended Tools for Diagnostics
When you're diagnosing modern vehicles, having the right tools makes all the difference. A basic code reader will only get you so far—you need tools that let you see what’s really going on and test components properly.
Autel MaxiSys MS906 Pro TS Professional OBD2 Scanner (with TPMS & full system diagnostics)
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This is a high-level scan tool that gives you full system access, including body control modules, along with bi-directional controls and TPMS diagnostics. It’s a must-have if you’re serious about diagnosing car problems.
Power Probe 3 (PP3CSRED) Circuit Testing Tool
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This is one of those tools you’ll use daily. It allows you to quickly verify power and ground and even activate components directly, cutting diagnostic time significantly.
Power Probe ECT3000 Circuit Tracer (Short & Open Finder)
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When you’re dealing with wiring issues, this tool helps you locate opens or shorts without tearing the vehicle apart. It saves time and prevents unnecessary damage during diagnostics.
Vehicle Overview
The vehicle in question is a 2021 Kia Seltos equipped with factory LED headlamp assemblies. Mileage wasn’t a major factor here, as the issue was clearly related to a component failure rather than wear and tear.
This model uses integrated LED lighting systems, meaning individual bulbs are not serviceable—you replace the entire assembly when something fails.
Vehicle Concern
The concern was straightforward:
The upper LED ring on the right front headlamp never worked. From the start, it was completely inoperative. However, the lower portion of the headlamp—low beam, high beam, and other functions—operated normally.
This kind of symptom is important when diagnosing car problems because it immediately tells you the failure is isolated, not a total loss of power to the assembly.
Initial Inspection & Observations
The first step in any good automotive troubleshooting process is a solid visual inspection.
Right away, one major issue stood out:
There was a visible crack in the right front headlamp housing.
That’s a big red flag.
Anytime you see physical damage to a sealed component like a headlamp assembly, you have to consider moisture intrusion. Water and electronics don’t mix, and modern LED assemblies are especially sensitive to contamination.
Aside from that, all other exterior lighting functions appeared normal.
Diagnostic Trouble Codes
A full system scan was performed to check for any related faults.
Result: No diagnostic trouble codes were stored.
That’s not unusual. Many lighting circuits—especially those involving LED driver circuits—won’t always set a fault code when there’s an internal failure.
This is where a lot of less experienced technicians get thrown off. No codes does NOT mean no problem.
Step-by-Step Diagnostic Process
Now we move into the real diagnostic work.
The goal here is simple: determine whether the problem is in the wiring/control side of the system or inside the headlamp assembly itself.
Step 1: Compare Left and Right Circuits
Whenever possible, always compare a known good side to the faulty side. It’s one of the most effective used car inspection tips and diagnostic strategies out there.
The left headlamp was fully functional, so it became our reference.
Both headlamp connectors were disconnected, and voltage and ground checks were performed on each side.
Step 2: Verify Power Supply
Power was checked at the connector for both the left and right headlamp assemblies.
Result: Both sides had identical voltage readings.
That tells us the power feed is good.
Step 3: Verify Ground Integrity
Next, ground circuits were tested.
Result: Grounds were solid and matched on both sides.
This eliminates one of the most common causes of lighting issues.
Step 4: Evaluate Control Signals
Depending on the system design, LED lighting may be controlled by the Body Control Module (BCM) using either constant voltage or a form of pulse-width modulation (PWM).
In this case, the behavior matched on both sides, indicating the control side of the circuit was functioning properly.
Step 5: Analyze the Results
At this point, we’ve confirmed:
Power is present
Ground is good
Control signals are working
Opposite side operates correctly
Yet the LED ring on the right side never illuminates.
This is where experience comes in.
When all external inputs are correct and the component still doesn’t function, the failure is internal.
Key Findings
Two key factors led to the final conclusion:
The upper LED ring never worked, while other functions in the same assembly did
There was a visible crack in the headlamp housing, allowing for potential moisture intrusion
This combination strongly points to an internal failure within the headlamp assembly—most likely damage to the LED circuit or driver module caused by moisture.
Final Diagnosis & Repair Recommendation
The right front headlamp assembly has an internal failure affecting the upper LED ring.
Because the LED components are not serviceable separately, the only proper repair is to replace the entire headlamp assembly.
There is no reliable or professional way to repair internal LED circuitry in these sealed units.
Common Causes of This Problem
From years of diagnosing car problems, here are the most common causes of issues like this:
Cracked or damaged headlamp housing allowing moisture intrusion
Internal LED driver failure
Manufacturing defects in LED assemblies
Corrosion on internal circuit boards
Thermal damage from prolonged heat cycles
Lessons for DIYers & Used Car Buyers
This is a perfect example of why a thorough inspection matters.
A cracked headlamp might seem like a cosmetic issue, but it can quickly turn into an expensive electrical problem. LED headlamp assemblies are not cheap, and many people don’t realize they can’t just replace a bulb.
If you’re looking at a used vehicle, always check:
Headlamp condition (look for cracks or moisture)
Proper operation of all lighting elements
Signs of condensation inside lenses
Catching something like this early can save you hundreds—sometimes thousands—of dollars.
Don’t Get Burned on Your Next Used Car
If you’re thinking about buying a used car—or even if you already have one—this is exactly the kind of problem that can slip through the cracks and cost you big money later.
After 35+ years in the automotive field, I’ve seen firsthand how often people end up with vehicles that have hidden issues just like this.
That’s why I put together a simple Used Car Guide to help you understand what to look for and how to avoid making a costly mistake.
It’s a quick, practical guide designed to give you the right mindset and approach before you buy.
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It’s a smart first step toward making a better used car decision.
Disclaimer: Some of the links in this post may be affiliate links, which means I may earn a small commission if you purchase through them—at no additional cost to you. I only recommend tools and products that I personally use or trust in real-world diagnostics.
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