Mercedes Active Headlamps Highbeam Light System Inoperative

Mercedes Active Headlamps Inoperative means the car has found a fault in the Intelligent Light System (ILS), so the adaptive functions, such as headlights that swivel into corners, automatic leveling and adaptive high beam, may stop working. The headlights themselves usually still turn on. At startup, Mercedes-Benz vehicles may display an error message stating that Active Headlamps are Inoperative.

Example of active headlamps inoperative warning.

Symptoms

Common error messages that come up on the instrument cluster:

• Active headlamps inoperative
• Intell. Light system inoperative
• Active light system inoperative
• Intelligent Light System Inoperative

The headlights will turn on, but they are not working properly.

This warning is common on Mercedes-Benz vehicles with Lighting Packages such as bi-xenon high-intensity discharge (HID) active headlights with headlight washers and corner-illuminating foglights. The active headlights progressively pivot toward the driver’s intended path, derived from how far the steering wheel has been turned left or right.

Corner-illuminating foglights throw a fixed beam of light in the direction the steering wheel is being rotated or whenever a turn signal is activated. These foglights function when the vehicle is traveling at speeds below 25 mph.

Possible Problems

The most common problems that trigger Active Headlamps Light System Inoperative.

Faulty Reflector Motor

It is likely that the motor that moves the low-beam reflector has failed or is not receiving power. Inside the headlight, you will notice one small motor and gear that connect to the low beam/projector lamp. When the motor is turned on, it moves the low beam, which is what is called the Active Light System.

The motor can fail due to high heat and water intrusion and trigger the active headlamp inoperative message. A short circuit can also cause the Active Light System to stop working. Check that 12-volt power is going to the headlight to power the motor. Check the motor for continuity to verify the motor isn’t defective.

If the motor has failed, it is not easy to replace. First, the headlight assembly must be removed. Then, you will need to open the headlight to access the motor. A temporary solution would be manually adjusting the low beam reflector/project to the proper position. The low beams will function as they do on cars without active headlights.

Blown Fuse

Check the fuses for the active headlight system. Depending on the model, the fuses will most likely be in the fuse box located in the trunk or side of the dashboard.

Bad Wires Harness

Check that the low beams are working. If they aren’t, there may be a problem with the wire harness that goes to the headlight or the wires inside the headlights. Make sure the wire harness is pressed firmly into the headlight assembly. The wires inside the headlight may also be damaged or shorted.

Headlight Module

A faulty headlight module can also be the reason why you may get active headlamps to stop working. The hardware inside the module can fail, most commonly due to corrosion or a software glitch that can prevent it from working properly. For further troubleshooting, read the fault codes with a Mercedes-Benz scanner. 

How do I know if my Mercedes has Active Headlamps?

The active headlamp system adjusts the low-beam reflector for better visibility and light projection based on vehicle speed and steering wheel position. Not all Mercedes-Benz vehicles have this feature. It is part of the Lightning Package, an add-on option for most models.

Mercedes vehicles that have active headlamps have the following code in the Datacard.

• 615: BI-XENON HEADLIGHT W.ACTVIE CURVE LIGHT RIGHT-DRIVE

Read the code before removing a headlight

Getting a headlight unit out of a modern Mercedes is most of the labor on this job, so it is worth knowing what you are going in for. The message itself does not distinguish between a failed reflector motor, a dead module, a blown fuse and a wiring fault, but the stored code does. These faults sit in the headlight and front SAM modules, which a basic engine code reader cannot reach, which is why so many of these cars scan clean at a parts store. A tool that addresses every module, such as the YOUCANIC UCAN-II Pro, will name the circuit and often the specific motor, and it will tell you which side before you take anything apart.

Water intrusion is the usual root cause

These headlight units are sealed with a breather, and when the seal perishes or the breather blocks, condensation sits inside and kills the stepper motors and the module electronics. If you find moisture or a tide mark inside the lens, fixing the electronics without fixing the seal just means doing it again next winter. Check that the drain and breather at the bottom of the housing are clear while the unit is out.

Repair is usually cheaper than a new headlight

A complete Mercedes active headlight assembly is one of the most expensive single parts on the car, and a replacement module has to be coded to the vehicle. Where the fault is in the control module or the ballast rather than the housing, having the original unit rebuilt returns your own module with its coding intact and costs a fraction of the assembly price. Worth pricing both before committing.

A failed bulb can set this message too

Before assuming the worst, check that both low beams actually light. The system monitors its own output, and a failed xenon bulb or igniter will report as a system fault rather than simply as a dead bulb. Xenon bulbs dim and shift color as they age, so a bulb that still lights but has gone pink or dim is near the end and can trigger intermittent warnings before it fails completely.

Frequently Asked Questions

Can I drive with the Mercedes active headlamps malfunction message?

Usually yes, since the headlights still work. But the beams may be aimed wrong and the swiveling may not work, so have it checked soon.

What causes the active headlamps warning?

A failed headlight swivel motor, a headlight control module, water inside the headlight or a bulb fault are common causes.

Will the message clear after a restart?

Sometimes. If it returns after switching the engine off and on, read the codes to find which headlight and part is at fault.

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