It usually means there's a fault in the daytime running light circuit—most often a burnt-out DRL bulb, a blown fuse, or a faulty control module. Start by inspecting the bulbs and fuses, and if the problem persists, have a technician diagnose the system.
What the warning means
Daytime running lights (DRLs) are designed to stay on during daylight to improve visibility. In modern cars, the DRL function is monitored by the vehicle’s lighting control system, and any abnormal condition can trigger a check DRL message on the dashboard. The warning indicates the DRLs may not operate as intended and should be inspected to ensure safety and compliance.
Below are the most common causes cited by technicians and vehicle manufacturers.
- Burnt-out or incompatible DRL bulb (LEDs or halogen)
- Faulty fuse or blown fuse in the DRL circuit
- Loose, corroded, or damaged wiring/connector
- Faulty DRL control module or body control module
- Aftermarket DRL installation or incorrect bulb wattage
- Battery or charging system issues causing voltage instability
In most cases, replacing a bulb or correcting a fuse resolves the alert. If the message persists or you notice DRLs not illuminating, professional diagnosis is recommended.
How to diagnose and fix
To identify and address the issue, follow these steps. Do not attempt invasive work if you're unsure; safety first and consult your owner's manual for model-specific guidance.
- Check the vehicle’s DRL bulbs: locate the DRL bulbs or the front headlight assembly. If DRLs are separate bulbs, inspect them; if the DRL shares the low/high beam bulb, ensure the other functions still operate.
- Inspect fuses and relays: locate the fuse box diagram in the owner’s manual, check the DRL fuse and associated relays for continuity or signs of a blown fuse.
- Inspect wiring and connectors at the front of the vehicle: look for damaged wires, loose connectors, corrosion, or moisture in the headlight area.
- Test the battery and charging system: a weak battery or failing alternator can cause voltage dips that trigger DRL warnings. Use a multimeter to check voltage (approximately 12.6V when the car is off, 13.5–14.7V when running).
- Check for diagnostic trouble codes: with an OBD-II scanner or dealership-level diagnostic tool, check for codes related to lighting or body control modules. Some cars store DRL faults as codes even if the warning disappears.
- Consider software/firmware updates or reprogramming: some DRL issues are resolved by a module software update at a dealership or service center.
- If you have installed aftermarket DRLs, ensure they are compatible with your vehicle and properly wired, or remove them temporarily to test if the warning clears.
After performing these steps, recheck DRL operation by turning on the ignition or starting the engine to ensure DRLs illuminate normally and the warning does not reappear. If the DRLs still fail or you’re unsure about parts replacement, seek professional service.
When to seek service
Schedule service if you observe any of the following: DRLs fail to illuminate, a warning remains after replacing bulbs or fuses, the message returns intermittently, or you notice dimming or flickering lights, which may indicate voltage issues or a failing module.
Notes for LED DRLs and aftermarket setups
LED DRLs and aftermarket kits require precise matching with the vehicle’s electrical system. Mismatched voltage, resistors, or wiring can trigger faults or fail to meet safety standards. If you have aftermarket lights, consider professional installation and, if needed, revert to OEM equipment to restore proper signaling and warnings.
Regulatory and safety considerations
In many regions, DRLs are either mandated or commonly required on new cars; functioning DRLs improve daytime visibility and reduce accidents. If your car fails the DRL system check, it could impact roadworthiness or insurance conditions, so addressing the issue promptly is prudent.
Summary
The DRL warning usually signals an issue in the daytime running light circuit, most often a bulb, fuse, or wiring problem, or a control module fault. Start with the simplest checks (bulbs and fuses) and move to electrical diagnostics or professional service if the warning persists. Keeping DRLs functioning not only maintains visibility but also helps meet safety and regulatory expectations.