How to replace 2018 Hyundai Elantra high mounted brake light?

The high-mounted brake light on a 2018 Hyundai Elantra is typically an LED module integrated into the light housing, so you generally replace the entire assembly rather than a single bulb.

This article walks you through how to identify whether your CHMSL is LED or bulb-based, locate it on your car, gather the right tools, and perform a safe replacement or upgrade. It covers both common scenarios and practical tips to avoid damage or moisture intrusion, with step-by-step guidance and testing afterwards.

Understanding the CHMSL on the 2018 Elantra

The Elantra’s third brake light is positioned at the high point of the rear end, often mounted in the trunk lid area or integrated into a rear glass/roof line depending on the exact trim. Most 2018 models use an LED CHMSL module that is not designed for bulb replacement; when the unit fails, the typical repair is to replace the entire light assembly. Some very early or rare configurations might still use a replaceable bulb behind a lens, but LED modules are far more common in this generation.

Tools and safety considerations

Prepare these basic tools and safety steps so you can work efficiently and avoid damaging trim or wiring.

• Trim removal tool (or a plastic pry tool) and a small screwdriver set


• Socket wrench (likely 8 mm or 10 mm) or appropriate driver for trunk-hinged screws


• Gloves and a flashlight for better visibility


• Replacement high-mounted brake light assembly (or LED module, if applicable)


• Optional: multimeter for checking electrical continuity and a few zip ties or electrical tape

With the right tools ready, you can proceed to identify the correct replacement path for your CHMSL and begin the removal process.

Step-by-step replacement paths

Two paths cover the most common configurations: LED-type CHMSL (the typical 2018 Elantra setup) and bulb-type CHMSL (less common but possible on some trims). Follow the path that matches your unit.

LED-type CHMSL (common for 2018 Elantra)

Note: LED CHMSLs are often not serviceable at the bulb level; most replacements require installing a new light assembly. The steps below outline the typical process for swapping the entire unit.

1. Park the car on a flat surface, engage the parking brake, and open the trunk. Remove the interior trunk liner around the CHMSL to access mounting screws or clips.


2. Disconnect the negative battery terminal to minimize the risk of shorts while you handle wiring.


3. Unclip or unscrew the CHMSL housing from its mounting position. Use the trim tool to release any clips without breaking the surrounding trim. Gently pull the light housing away from the vehicle while supporting the wiring.


4. Carefully unplug the electrical connector from the back of the CHMSL. Inspect the connector and wiring for any corrosion or damage.


5. Remove the old LED light assembly and compare it to the replacement part for compatibility (shape, mounting holes, and connector). Install the new light by reconnecting the harness and guiding the unit into place.


6. Secure the new CHMSL with the original screws or clips. Reinstall the trunk liner, ensuring no wires are pinched.


7. Reconnect the battery negative terminal. With the trunk open, have a helper press the brake pedal to verify the new light functions correctly (all LEDs should illuminate steadily when braking).


8. Close the trunk and confirm alignment and brightness from outside the vehicle. If the light is dim or inconsistent, recheck the connector and mounting.

Once installed, an LED CHMSL replacement typically restores full brake light functionality and may come with a warranty from the part manufacturer or dealer.

Bulb-type CHMSL (if applicable)

Some older or less common configurations might use a replaceable bulb behind a lens. If your Elantra uses a bulb, follow these steps to replace just the bulb rather than the entire unit.

1. Open the trunk and remove the interior trim from around the CHMSL to expose the lens and bulb housing.


2. Twist or pry off the lens cover to gain access to the bulb socket. Note the bulb type and its orientation for a correct replacement.


3. Remove the old bulb by gently pulling it straight out or twisting counterclockwise, then insert a fresh bulb of the same specification. Avoid touching the glass with your fingers; use gloves or a clean tissue to handle the new bulb.


4. Reinstall the lens, ensuring a secure seal against moisture. Reassemble the trunk liner and verify the light with the brake pedal press.


5. If you notice flickering or no light after replacement, check the bulb seating, socket contacts, and connector integrity. Replace the housing if internal components are damaged.

Bulb-based CHMSLs are generally cheaper upfront but might require more frequent maintenance due to bulb lifespan and moisture ingress in the lens seal.

Testing, resealing, and what to do next

After completing the replacement, test the system thoroughly. Confirm that the new light illuminates during braking, and verify that the other rear lights and turn signals remain functional. Recheck the trunk seals and trim installation to prevent water intrusion, and keep a spare replacement bulb or module in the vehicle in case of future faults.

Summary

For the 2018 Hyundai Elantra, the high-mounted brake light is most often an LED module that requires replacing the entire assembly rather than a bulb. Start by identifying whether your CHMSL is LED-based or bulb-based, gather the appropriate tools, and follow the corresponding replacement path. Whether you replace the whole unit or swap a bulb behind a lens, careful disassembly of the trunk area, secure reconnection of electrical plugs, and a final testing round will ensure a safe, functional result and restore the vehicle’s brake-light performance. If in doubt, consult an authorized Hyundai technician or refer to the vehicle’s service manual for model-specific instructions and part numbers.