How do you check the DRL system on an Acura?
Most Acura models use daytime running lights (DRLs) that come on automatically when the ignition is on. If you don’t see DRLs, use this practical diagnostic guide to identify common issues, from bulbs and fuses to wiring and control modules.
Understanding Acura DRLs
Daytime running lights are designed to improve daytime visibility. In many Acura vehicles, DRLs are either dedicated LED modules or the low-beam headlights that operate at reduced power. Depending on the model and year, DRLs may behave differently when you switch to Auto headlights or when other lighting systems are engaged. This section explains how the system is typically wired and what you might expect to see on your specific Acura.
Model variations you should know
Acura DRLs can vary by generation and trim. Some models use separate DRL modules inside the headlight assembly, while others rely on the same bulbs used for low beams. If you replaced a bulb or module, ensure the part is compatible with your exact model year and that any required wiring harnesses or control modules are correctly connected.
Checklist: Visual and Initial Checks
Start with a quick visual assessment to catch obvious problems before diving deeper.
- Inspect DRL bulbs or LED modules for signs of burn marks, dull illumination, moisture, or physical damage inside the headlight housing.
- Look for loose or corroded connectors, damaged wiring, or melted insulation around the DRL harness.
- Verify that the ignition is on and the vehicle is in a mode where DRLs should be active; on some models, DRLs behave differently when Auto headlights are selected.
Conclusion: If you find a burnt-out bulb, water intrusion, or a loose connector, address that issue first. LED DRLs may require a full assembly replacement if individual LEDs fail.
Electrical Diagnosis: Fuses, Relays, and Modules
When visual checks don’t reveal the culprit, inspect the electrical components that govern DRLs. This section covers where to look and how to test safely.
- Check the DRL fuse(s) in the vehicle’s fuse box according to the owner's manual; replace any blown fuse with the correct amperage.
- Inspect related relays or the DRL control module; listen for a relay click when you turn the ignition on if the system uses a relay.
- Ensure the 12-volt battery is healthy, as low voltage can cause DRLs to underperform or fail to light.
Conclusion: If fuses and relays are intact but DRLs still don’t operate, the issue may lie with the DRL control module or wiring, which often requires diagnostic software or professional inspection.
Testing the DRL Circuit (Safe, Non-Invasive)
These steps help you verify operation and identify where the circuit might be failing without disassembling headlight assemblies.
- With the ignition on, observe whether DRLs illuminate; if not, test the voltage at the DRL connector with a multimeter during the period DRLs should be active.
- Check for approximately 12 volts at the DRL harness when the vehicle should have DRLs on; absence of voltage points to a power supply or wiring fault.
- For vehicles with LED DRLs, some models require a service scan or firmware check to reset the system after replacement; consult the dealer or service manual if LEDs are not lighting despite power.
Important: If you’re not comfortable testing live circuits or accessing the DRL connector, seek professional assistance to avoid damage or injury.
When to See a Technician or Dealership
Persistent DRL failures often indicate a deeper issue in the lighting circuit, body control module (BCM), or related wiring. A professional diagnosis ensures proper repair and helps protect warranty coverage.
What a technician may check
A technician will typically verify BCM integration, read OEM diagnostic codes, test the DRL circuit for continuity and resistance, and inspect headlight assemblies for moisture or seal failures. They may also reprogram or update the DRL system if required by a service bulletin.
Maintenance Tips to Prevent DRL Failures
Preventive care can keep DRLs reliable and reduce future outages.
- Keep headlight housings clean and dry; address condensation or water intrusion to prevent corrosion or short circuits.
- Regularly inspect fuses and connectors for corrosion or looseness; apply dielectric grease where recommended by the manual.
- Use OE-recommended bulbs or modules; incompatible parts can trigger lighting faults or improper DRL operation.
Bottom line: Routine checks and using proper parts help maintain DRL performance and daytime visibility.
Conclusion and Takeaways
DRLs are a safety feature on Acura vehicles designed to boost daytime visibility. A structured check—visual inspection, fuse/relay verification, and, if needed, voltage testing or professional diagnostics—covers most common problems. If in doubt, consult an Acura dealership or a qualified automotive lighting specialist to avoid incorrect repairs or warranty issues.
Summary: Acura DRLs typically light automatically with ignition; if they don’t, begin with a visual inspection, then move to fuses/relays, and finally consider professional diagnostic steps. Address any moisture, damaged components, or incompatible parts promptly to maintain reliable daytime visibility.
