How to Fix Fading or Broken Daytime Running Lights on Your 2018-2020 Mercedes-Benz W222: Step-by-Step Replacement

TL;DR

On the 2018-2020 Mercedes-Benz W222, the daytime running lights often fail due to a burned-out LED board or a yellowed, cracked light guide strip inside the headlight. Replacing the DRL light guide strip and LED board restores full brightness without replacing the entire headlight assembly.

What Goes Wrong with W222 DRLs

The W222's DRL system uses a flexible light guide strip that channels light from an LED board. Over time, heat cycling from the LEDs causes the light guide to yellow and develop micro-cracks, while the LED board itself can suffer from solder fatigue or moisture ingress. The result: one or both DRLs appear dim, patchy, or completely dead. A DRL light guide strip and LED board is the internal component that distributes and emits the daytime running light—it is not the outer lens or the main headlight bulb.

Diagnosing the Issue

First, check if the DRL is completely out or just dim. If one side is noticeably brighter, the other side's LED board or light guide is likely failing. Inspect the headlight housing for condensation, which points to moisture ingress. A quick voltage test at the DRL connector can confirm power is reaching the unit. If power is present but the light is weak or absent, the internal LED board or light guide is the culprit. No fault codes are typically stored for this, so visual and electrical checks are key.

Step-by-Step Replacement

1. Disconnect the battery negative terminal. 2. Remove the front bumper or access the headlight from the wheel well, depending on your tools. 3. Unbolt the headlight assembly and pull it forward. 4. Remove the back cover of the headlight to access the DRL module. 5. Unplug the old LED board and carefully detach the light guide strip. 6. Install the new light guide strip and LED board, ensuring all clips and connectors seat fully. 7. Reassemble in reverse order. Approximate DIY time: 1-2 hours per side. On the Mercedes-Benz W222 the connector is factory-matched and no wiring is touched. If a warning appears it comes from the car's lamp monitoring, not the part.

Fitment Tips

This DRL light guide strip and LED board is designed specifically for the 2018-2020 Mercedes-Benz W222 S-Class. Confirm your model year and headlight type (LED or higher) before ordering. Handle the light guide by its edges to avoid fingerprints or scratches. During reassembly, check that the rubber seals are properly seated to prevent future moisture ingress. A little dielectric grease on the connectors can help keep corrosion at bay.

Fix vs Replace

Fit and go on most Mercedes-Benz W222 cars. Where a warning does appear it is the lamp self-check, cleared by coding rather than by swapping parts. The table below compares the two options: | Option | Cost Scale | Install Time | What You Keep | |--------|------------|--------------|---------------| | DRL Light Guide & LED Board | A fraction of the cost of a new headlight assembly | 1-2 hours | Original housing, lens, and main beam | | New Headlight Assembly | Dealer/OEM: high (often $1,500-$3,000+ per side) | 2-4 hours + coding | Nothing—full replacement | For most W222 owners, replacing just the DRL components is the smarter fix.

Recommended Part

For a direct fit and reliable performance, we recommend the Mercedes-Benz S-Class W222 DRL Light Guide Strip & LED Board (2018-2020). The Mercedes-Benz W222 needs nothing beyond the swap in most cases; the exception is cars that monitor their lamps and log a fault until the check is disabled. Restore your S-Class's signature daytime running lights without the expense of a full headlight replacement.

FAQ

Q: Is any coding involved?

A: Most Mercedes-Benz W222 cars are plug-in and done. A few log a fault until the lamp check is coded off; ask us if your car is particular about lamp diagnostics.

Q: Is this an afternoon job or a weekend one?

A: Typically 1-2 hours per side for a DIY install, depending on your tools and experience.

Q: Can I replace just the light guide without the LED board?

A: It is recommended to replace both together, as they are designed to work as a set and wear similarly.

Q: Does the part carry any cover?

A: A one-year warranty applies, covering defects.

Standards reference: for the Mercedes-Benz W222, the daytime running lamp is governed by UN ECE Regulation 148 (which superseded R87) in most markets and by FMVSS 108 in the United States - these define when the lamp runs and at what output. Fresh board or guide, same regulated function the car left the factory with.