Daytime Running Lights Not Working

You get in your car, turn the ignition, and notice something’s off. Your daytime running lights, or DRLs, are not working. This common issue can be frustrating, but it’s often something you can diagnose yourself. This guide will help you understand why your Daytime Running Lights Not Working and what you can do about it.

DRLs are a crucial safety feature. They make your vehicle more visible to other drivers during daylight hours. When they fail, it’s not just an inconvenience—it can be a safety risk. Let’s look at the common causes and fixes.

The first step is understanding what you’re dealing with. Daytime running lights are designed to come on automatically when your vehicle is running and the regular headlights are off. They are usually a lower intensity than your headlights. When they don’t illuminate, the problem could be simple or complex.

Common Reasons Why DRLs Fail

Several components work together to make your DRLs function. A failure in any one can cause the system to stop working. Here are the most likely culprits:

Blown Bulbs: This is the most common cause. DRLs are on whenever you drive, so their bulbs have a high duty cycle and can burn out.
Blown Fuse: A dedicated fuse protects the DRL circuit. A power surge or fault can cause it to blow.
Faulty DRL Module/Relay: Many cars have a seperate control module or relay that powers the DRLs. This can fail over time.
Bad Wiring or Connection: Corrosion, loose connectors, or damaged wires can interrupt the electrical circuit.
Faulty Light Sensor: The system uses a sensor to determine if it’s day or night. A malfunctioning sensor might not activate the DRLs.
Settings or Switch Error: Some vehicles allow you to disable DRLs through dashboard settings or a physical switch that may have been accidentally toggled.

Step-by-Step Troubleshooting Guide

Follow these steps in order. Start with the simplest and cheapest possibilities before moving to more complex ones.

Step 1: Perform a Basic Visual Check

Before you touch any tools, do a quick inspection. Turn on your vehicle and check if the DRLs are truly off. Sometimes, in bright sunlight, they can be hard to see. Also, verify that your headlight switch is in the “off” or “auto” position, as DRLs typically turn off when headlights are manually engaged.

Step 2: Check Your Vehicle Settings

Modern cars have digital menus. Use your steering wheel or dash controls to navigate to the lighting settings. Ensure the DRL function is enabled. Consult your owner’s manual for specific instructions—it’s surprising how often this is the fix.

Step 3: Inspect and Replace the Bulbs

If the settings are correct, the bulbs are the next suspect. Here’s how to check them:

Locate the DRL bulbs. They may be in the headlight assembly or a separate housing. Your manual will show you.
Carefully remove the access cover or the entire headlight assembly if needed.
Remove the bulb socket. Inspect the bulb for a broken filament or dark clouding inside the glass.
If it looks bad, replace it with an identical bulb. Use gloves or a cloth to handle new halogen bulbs—skin oils can cause them to fail prematurely.

Step 4: Locate and Test the DRL Fuse

If both bulbs are out, a blown fuse is very likely. Find your fuse box (usually under the dash or in the engine bay). The lid should have a diagram showing which fuse is for the DRLs.

Use the fuse puller tool (often in the fuse box) to remove the suspect fuse.
Hold it up to the light. The metal strip inside should be intact. If it’s broken or melted, the fuse is blown.
Replace it with a new fuse of the exact same amperage. Never use a higher-amp fuse, as this can cause a fire.

Step 5: Investigate the DRL Control Module

The module is a small electronic box that controls the lights. It’s often located under the dash or in the engine compartment. Finding it can require some online research for your specific car model.

Testing it properly usually requires a multimeter, but you can sometimes identify a faulty module by signs of physical damage, burning smells, or by swapping it with a known good unit (if accessible). This step might be best left to a mechanic if you’re uncomfortable.

Step 6: Look for Wiring Issues

Inspect the wiring harness leading to the DRLs. Look for:

Frayed or chewed wires (pests can be a problem).
Corroded or loose connectors at the bulb socket or module.
Signs of moisture inside the light housing, which can cause shorts.

Cleaning connectors with electrical contact cleaner can sometimes restore the connection.

Step 7: Test the Ambient Light Sensor

This sensor is usually on the top of the dashboard, near the windshield. If it’s covered by an object (like a GPS unit or a dash mat), it might think it’s nighttime. Clean the sensor’s surface. Diagnosing a truly faulty sensor usually requires a professional scan tool.

When to Call a Professional Mechanic

If you’ve gone through all these steps and your daytime running lights are still not working, it’s time for expert help. A certified mechanic has the tools and diagrams to perform advanced diagnostics. They can:

Perform a full scan of your vehicle’s body control module for error codes.
Perform precise voltage and resistance tests on the entire circuit.
Trace wiring faults that are hidden behind panels or in the harness.
Correctly program a new control module if needed.

Investing in a professional diagnosis can save you money on unnecessary parts and a lot of time.

Preventive Maintenance Tips

To avoid future problems with your DRLs, consider these simple habits:

During regular car washes, visually check that all exterior lights are working.
When you replace a headlight or signal bulb, consider replacing the DRL bulb on the same side if they’re the same age.
Keep your vehicle’s fuse box diagram in a safe place; it’s invaluable for troubleshooting.
Address moisture in light housings immediately to prevent corrosion and bulb failure.

Following these tips can help you catch a small problem before it leaves you driving with impaired visibility.

FAQ: Daytime Running Light Problems

Can I drive with my DRLs not working?

While it’s not illegal everywhere, it is strongly discouraged. DRLs significantly improve your vehicle’s visibility to others. Driving without them increases your risk of a collision, especially at dawn, dusk, or in poor weather. Check your local laws, as some regions mandate their use.

Are daytime running lights the same as my headlights?

No. DRLs are a separate, dimmer system that operates only during the day. They are not designed to illuminate the road. Your headlights, fog lights, and high beams are for actual driving illumination in dark conditions.

Why did only one DRL stop working?

This almost always points to a problem isolated to that side. The most common causes are a single blown bulb, a bad connection in that specific socket, or a wiring issue on that circuit. Start by checking and replacing the bulb on the non-working side.

How much does it cost to fix DRLs?

Costs vary widely. A DIY bulb replacement might cost $20-$50. A fuse is just a few dollars. If you need a professional, labor rates apply. Replacing a control module or repairing complex wiring could cost anywhere from $150 to $500 or more, depending on the vehicle and the shop.

Can a dead car battery affect DRLs?

A very low battery can cause all sorts of electrical gremlins, including DRL failure. However, if the car starts and runs, the battery is likely not the direct cause of only the DRLs not working. It’s more likely a specific component in the DRL circuit has failed.

Figuring out why your daytime running lights are not working can feel like a puzzle. But by starting with the simple checks—like settings and bulbs—you can often solve the problem quickly and cheaply. Remember, keeping these lights functional is a simple step toward safer driving for everyone on the road. If the issue proves to complex, don’t hesitate to seek a professional opinion to get your safety features back in working order.