Daytime Running Lights Not Working - Top Causes, Fixes & What to Do

Certified Professional Automotive Mechanic – Owner and Editor of VehicleRuns

Last Updated: November 3, 2026

Safety note: Troubleshooting guidance can help you narrow down likely causes, but it cannot replace an in-person inspection. If the vehicle feels unsafe, warning lights are flashing, you smell fuel, see smoke, notice overheating, or have problems with braking, steering, or control, stop driving when it is safe to do so and have the vehicle inspected.

If your daytime running lights are not working, the problem is usually somewhere in the lighting power supply, control side, or the lamps themselves. On many vehicles, DRLs do not act like simple always-on bulbs. They may depend on a relay, a fuse, an ambient light input, a body control module command, or a reduced-voltage headlamp circuit.

That is why the symptom pattern matters. One side out points you more toward a bulb, socket, or local wiring issue. Both sides out at the same time pushes suspicion toward a fuse, relay, module command, sensor input, or shared ground or feed problem.

This guide helps you narrow it down by checking what still works, when the DRLs fail to come on, and whether the fault looks like a simple lamp issue or a deeper electrical control problem.

Start by figuring out whether one DRL is out or both, and whether the regular headlights still work. That split usually tells you whether to begin with the bulb and socket, or the shared fuse, relay, sensor, or control circuit.

What you notice	Most likely cause	What to check first	Urgency
Only one daytime running light is out	Burned-out bulb or socket	Swap or inspect that bulb and socket for heat damage	Diagnose soon
Both DRLs quit at the same time	Blown fuse or bad relay	Check DRL-related fuses and relays in the fuse boxes	Diagnose soon
Headlights work, but DRLs never come on	Control circuit fault	Confirm parking brake, switch settings, and ambient light sensor behavior	Can worsen
DRLs work intermittently over bumps	Loose wiring or connector	Inspect lamp connectors, grounds, and harness routing near the lamps	Can worsen
Dash shows lighting warnings or multiple lights affected	Module or power supply problem	Scan body control module and test system voltage	Can worsen

Best first move: First confirm the DRL operating conditions for your vehicle, then check whether the fault is one side only or both sides before chasing wiring or modules.

Safety note: You can usually drive a short distance in daylight if normal headlights, turn signals, and brake lights still work, but do not ignore a wider lighting or charging problem if other lamps are also acting up.

Table of Contents

Most Common Causes of Daytime Running Lights Not Working

Most DRL failures come down to a few common issues, especially when you match the failure pattern first. A fuller list of possible causes appears later in the article.

Blown Fuse, Bad Relay, or Power Supply Problem: If both daytime running lights stop working together, a shared fuse, relay, or feed circuit is one of the first things to suspect.
Burned-Out DRL Bulb or Failed Lamp Unit: When only one side is out, the most common cause is still the bulb, LED board, or lamp assembly on that side.
Wiring, Connector, or Electrical Ground Fault: Corrosion, heat-damaged sockets, loose connectors, or bad grounds can cause one or both DRLs to fail or work intermittently.

What Daytime Running Lights Not Working Usually Means

Daytime running lights not working usually means the DRL circuit is losing either power, ground, or the command that turns it on. On older vehicles that may be a straightforward bulb, fuse, or relay issue. On newer vehicles, DRL operation is often managed by a body control module and may depend on inputs like ambient light, transmission position, engine running status, or parking brake position.

If only one side is out, think local first. A failed bulb, bad LED driver inside the lamp, melted socket, or broken wire near that lamp is much more likely than a central module failure. If both sides quit together, look first at what both lights share: fuses, relays, common grounds, or a DRL control module or body control command.

It also matters whether the normal low beams and high beams still work. If the headlights work normally but DRLs do not, the problem is often in the dedicated DRL function rather than the entire headlamp circuit. If other exterior lights are acting strange too, widen the diagnosis to charging voltage, grounds, wiring damage, or a control module issue.

Another common mistake is diagnosing a working system as failed because the DRLs only operate under certain conditions. Some vehicles turn them off when the parking brake is set, when the headlight switch is in certain positions, or when the ambient light sensor commands full headlights instead.

Possible Causes of Daytime Running Lights Not Working

Blown Fuse, Bad Relay, or Power Supply Problem

Most DRL systems have a shared fuse, relay, or power feed. When that shared supply fails, both daytime running lights usually stop working at once even though other lighting functions may still operate.

Symptoms to Watch For

Both DRLs stopped working together
No power at both lamp connectors
A recent jump start or electrical issue preceded the failure
Other low-current body electrical functions may also act odd

Moderate Severity

A simple fuse or relay issue is not usually dangerous by itself, but it reduces visibility to others and can also point to a deeper short or electrical fault if it returns.

How to Confirm: Check the owner's manual or fuse-box legend for DRL, headlamp, BCM, or exterior lighting fuses and relays.

Typical fix: Replace the failed fuse or relay, and repair any shorted power feed or related supply issue if the replacement fails again.

Burned-Out DRL Bulb or Failed Lamp Unit

Many DRL systems still use dedicated bulbs or a bulb filament shared with another lighting function. On newer vehicles, an internal LED board or driver can fail inside the lamp assembly. Either failure usually affects one side first.

Symptoms to Watch For

Only one DRL is out
The other side still works normally
The failed side may have a dark, clouded, or moisture-damaged lamp
A bulb replacement may bring the DRL back immediately

Low Severity

One failed DRL is usually not an immediate safety emergency in daylight, but you still need to correct it because it affects visibility and may indicate lamp or socket heat damage.

How to Confirm: Inspect the failed lamp closely and compare it to the working side. Remove the bulb if serviceable and look for a broken filament, darkened glass, or heat damage. If it uses an integrated LED lamp, verify power and ground at the connector; good power and ground with no DRL output points to a failed lamp unit.

Typical fix: Replace the failed DRL bulb, LED module, or complete lamp assembly depending on how the vehicle's DRL is built.

Wiring, Connector, or Electrical Ground Fault

DRL circuits live in an exposed area near the front of the vehicle where heat, moisture, vibration, and road splash can damage connectors, corrode terminals, or weaken grounds. That can cause a dead lamp, intermittent operation, or dim output.

Symptoms to Watch For

DRLs flicker or work intermittently
The problem changes over bumps or after rain
A socket looks melted or green with corrosion
One side is dimmer than the other

Moderate Severity

Wiring faults can stay minor for a while, but corrosion and heat damage usually get worse and can eventually affect more lighting functions or blow fuses.

How to Confirm: Inspect the lamp connector, harness, and nearby ground point for corrosion, looseness, broken insulation, or overheated terminals.

Typical fix: Repair the damaged wiring, clean or replace the connector, and restore the ground connection or terminal tension.

Ambient Light Sensor or Control System Fault

On many vehicles, the DRL function depends on light sensor input and body control logic. If the system thinks it is dark, in park, or in a mode that disables DRLs, the lamps may never come on even though the bulbs and wiring are fine.

Symptoms to Watch For

Headlights behave oddly in auto mode
DRLs do not come on only in certain switch positions
The issue started after battery service or module reset
No physical damage is visible at the lamps

Moderate Severity

This is usually not immediately hazardous in daylight, but it can be frustrating to diagnose and may affect other automatic lighting functions too.

How to Confirm: Verify the exact DRL operating conditions for the vehicle first, including engine running status, gear position, parking brake release, and headlight switch position. Then use a scan tool that can read body control data to see whether the ambient light sensor and DRL command states make sense. Incorrect sensor data or a missing DRL command with correct conditions supports this cause.

Typical fix: Replace the failed ambient light sensor or correct the control-system issue, then perform any needed module reset, relearn, or programming procedure.

Body Control Module or DRL Control Module Fault

Some vehicles use the body control module or a dedicated DRL module to switch power, modulate voltage, or decide when the DRLs should operate. Internal module faults can disable DRLs even when fuses, bulbs, and wiring look normal.

Symptoms to Watch For

Both DRLs are inoperative with good bulbs and fuses
Lighting warning messages are present
Other body electrical features may also act up
The fault may begin after low voltage or water intrusion

Moderate to High Severity

A module problem is usually not a stop-driving issue by itself, but it can affect multiple lighting functions and often needs proper electrical testing before parts are replaced.

How to Confirm: Scan the body control module for stored lighting-related trouble codes and check whether it is commanding the DRLs on under the correct conditions. If the module command is missing or the output circuit does not respond despite verified powers, grounds, and inputs, the control module or integrated driver becomes the likely fault.

Typical fix: Replace or reprogram the faulty body control module or DRL control module and correct any related low-voltage or water-intrusion issue.

Headlight or Lamp Housing/Lens Problem

Some DRL systems are built into the headlamp assembly, and internal damage from moisture intrusion, broken circuit boards, or overheated components can disable the DRL portion while other lights still work.

Symptoms to Watch For

Condensation or water inside the lamp
Burn marks inside the housing
Integrated LED DRL strip is dark
Connector power and ground test good

Moderate Severity

This is not usually urgent from a driveability standpoint, but moisture inside the lamp tends to worsen and can damage more of the lighting assembly over time.

How to Confirm: Inspect the housing for moisture, cracks, and internal heat damage.

How to Diagnose a Foggy or Moisture-Filled Headlight

Typical fix: Replace the damaged headlight or lamp assembly and correct any sealing or mounting issue that allowed water entry.

How to Diagnose the Problem

Confirm the DRLs are actually supposed to be on under the current conditions, including engine running, parking brake released, and the correct switch position.
Check whether one DRL is out or both are out. That single clue changes the diagnosis more than most owners realize.
Verify whether the low beams, high beams, parking lights, turn signals, and other front lighting functions still work normally.
Inspect the affected lamp or both lamps for obvious bulb failure, moisture, melted sockets, or physical damage inside the housing.
Check the DRL-related fuses first, then test or swap the relay if the system uses one.
Measure voltage and ground at the affected lamp connector or at both connectors if both sides are out.
Inspect harness routing near the radiator support, headlamp mounts, and front bumper area for rubbing, corrosion, or collision-related damage.
If the wiring looks good, verify system voltage and battery condition, especially if other electrical functions are acting strange.
Use a scan tool that can access body or lighting modules to look for lighting codes, sensor data, and DRL command status.
If power, ground, and operating conditions all check out but the DRLs still do not work, move toward a control module or integrated lamp failure diagnosis.

Can You Keep Driving if the Daytime Running Lights Are Not Working?

Important: The guidance below is general and cannot confirm that your specific vehicle is safe to drive. If a symptom affects braking, steering, handling, fuel, overheating, smoke, visibility, or vehicle control, treat it as potentially serious and have the vehicle inspected before continued driving when appropriate. For more context, see our Automotive Safety Disclaimer.

In most cases, a DRL problem does not affect how the engine or brakes work, so this is mainly a visibility and legal-compliance issue rather than a mechanical driveability problem. Still, how safe it is to continue depends on whether the fault is limited to the DRLs or part of a larger lighting or electrical problem.

Okay to Keep Driving for Now

Usually acceptable for short daytime driving if the regular headlights, brake lights, turn signals, and other required exterior lights still work normally and there are no broader electrical issues.

Maybe Okay for a Very Short Distance

Use caution if you are not sure whether only the DRL function is affected, or if one lamp works intermittently due to a loose connector. Limit driving until you confirm that full headlight operation is still normal.

Not Safe to Keep Driving

Do not keep driving if the failure is part of a wider electrical problem, multiple exterior lights are out, fuses keep blowing, wiring is overheating, or battery and charging symptoms are showing up too.

How to Fix It

The right fix depends on whether the failure is in the lamp itself, the shared power supply, the wiring, or the control side. Many DRL problems are straightforward once you confirm whether the issue is one-sided or system-wide.

DIY-friendly Checks

Check the owner's manual for DRL operating conditions, inspect bulbs and lamp housings, test fuses, and look for obvious corrosion or heat damage at the lamp connectors.

Common Shop Fixes

A repair shop will commonly replace failed bulbs, sockets, relays, lamp assemblies, or damaged front-end wiring once power and ground testing points to the bad component.

Higher-skill Repairs

Module diagnosis, scan-tool command testing, voltage-drop testing, and body control module replacement or programming are the deeper repairs when the simple lamp and fuse checks do not solve it.

Related Repair Guides

Typical Repair Costs

Repair cost depends on the vehicle, the DRL design, and whether the failure is a simple lamp issue or a control-side electrical fault. The ranges below are typical U.S. parts-and-labor estimates, not exact quotes for every make and model.

DRL Bulb Replacement

Typical cost: $20 to $120

This usually applies when the DRL uses a serviceable bulb and access is straightforward.

Fuse or Relay Replacement

Typical cost: $15 to $80

This is the lower-cost fix when the issue is limited to a failed fuse or a plug-in relay.

Socket or Wiring Repair

Typical cost: $100 to $300

Cost rises if corrosion has spread into the harness or the front bumper and lamp area need disassembly.

Headlight or DRL Lamp Assembly Replacement

Typical cost: $250 to $1,200+

Integrated LED headlamp units can get expensive fast, especially on newer vehicles with sealed assemblies.

Ambient Light Sensor or Control Input Repair

Typical cost: $100 to $350

This range usually covers diagnosis plus replacement of a failed sensor or correction of a related input fault.

Body Control Module Diagnosis and Replacement

Typical cost: $300 to $1,000+

Module work often includes electrical testing, programming, and in some cases relearn procedures.

What Affects Cost?

Whether the DRL uses a replaceable bulb or an integrated LED lamp
How much front-end disassembly is needed to access the lamp or wiring
Local labor rates and diagnostic time
OEM versus aftermarket lamp or module pricing
Whether the failure is isolated or part of a larger electrical issue

Cost Takeaway

If only one side is out, the repair often stays in the lower to middle cost range unless the lamp is a sealed LED unit. If both sides quit together, expect to start with inexpensive fuse and relay checks, but costs climb if testing leads to wiring repair or module work.

Symptoms That Can Look Similar

Parts and Tools

FAQ

Why Would Both Daytime Running Lights Stop Working at the Same Time?

When both sides fail together, look first for what they share: a fuse, relay, common power feed, shared ground, or a control module or sensor input problem. Dual bulb failure at the exact same time is possible, but less common.

Can a Bad Battery Cause Daytime Running Lights Not to Work?

It can, especially if system voltage is unstable or low enough to confuse the body control module. If other electrical issues are showing up too, check battery condition and charging voltage along with the DRL circuit.

Do Daytime Running Lights Have Their Own Fuse?

Some vehicles do, and others combine DRL protection with a broader exterior lighting or body control circuit. The fuse-box legend and wiring diagram are the best way to confirm how your vehicle is set up.

Why Do My Daytime Running Lights Work Sometimes but Not Always?

Intermittent DRLs often point to a loose connector, corrosion, wiring movement, or a control input issue such as an ambient light sensor or parking brake switch signal. Temperature and bumps can make the symptom appear and disappear.

Can I Get Pulled Over for Daytime Running Lights Not Working?

That depends on local law and whether the vehicle still meets required lighting rules. Even where DRLs are not strictly required, a nonworking lamp can still lead to reduced visibility or attention from law enforcement if other lighting problems are present.

Final Thoughts

The fastest way to narrow down daytime running lights not working is to split the problem into one side versus both sides, then confirm whether the rest of the lighting system still works normally. That keeps you from jumping straight to expensive module guesses when the fault is often a bulb, fuse, connector, or ground.

Start with the simple checks that match the symptom pattern, then move into voltage, ground, and control testing if those basics do not explain it. DRL faults are often minor, but a broader lighting or electrical problem deserves quicker attention.