The 2018 Hyundai Elantra’s center high-mount stop lamp sits at the top of the rear hatch. Depending on the trim, it may be a replaceable bulb or an integrated LED module; replacement procedures differ accordingly. This guide covers both scenarios, plus safety tips and when to seek professional help.
Identify your CHMSL type
Before beginning, determine whether your Elantra’s third brake light is a replaceable bulb or a sealed LED module. If brake light activation shows individual diodes, it’s an LED unit; if there’s a bulb socket or you can replace a bulb, it’s bulb-based. The owner’s manual or a Hyundai parts dealer can confirm the exact type for your VIN.
Bulb-based third brake light
If your CHMSL uses a replaceable bulb, follow these steps to swap it out. Gather a few common tools and prepare for trim removal.
- Park on a level surface, switch off the vehicle, engage the parking brake, and (for extra safety) disconnect the negative battery terminal.
- Open the trunk and carefully remove the interior trim panel around the CHMSL. Use a trim tool or a plastic prying tool to release plastic clips without scratching the surface.
- Disconnect the electrical connector from the back of the light housing and set the housing aside.
- Twist the bulb socket counterclockwise to unlock, then pull it out to remove the old bulb.
- Install a new bulb of the same type and size as the original. Reinsert the socket into the housing and twist clockwise to lock it.
- Reconnect the electrical connector, reattach the CHMSL housing, and snap the trunk lining back into place.
- Test the brake light by having someone press the brake pedal while you observe the light to ensure it illuminates steadily.
After replacing, recheck the interior trim fit and weather seal to guard against water intrusion, and verify the light remains reliable during regular use.
LED third brake light
On many 2018 Elantra models, the CHMSL is an LED module and is not designed for field servicing. If the LED array fails, the standard path is to replace the entire CHMSL assembly. Follow these general steps if you’re replacing the full unit.
- Park and, for safety, disconnect power. Open the trunk and inspect the CHMSL mounting area for screws or brackets.
- Remove any trim pieces or the tailgate liner as needed to access the CHMSL mounting screws or bolts.
- Disconnect the electrical harness from the LED module. Keep track of any washers or spacers for reassembly.
- Remove the old CHMSL assembly by unfastening screws or clips and carefully pulling it clear of the tailgate.
- Install the replacement LED CHMSL, align with mounting holes, reconnect the harness, and secure with screws or bolts.
- Reinstall the trim and test the light by applying the brake with the engine off and again with the engine running to confirm proper operation and brightness.
Note that LED replacements may require part compatibility checks for your VIN, and, in some cases, dealer programming or calibration may be referenced by the seller or a qualified technician. If in doubt, consult a professional to ensure proper fit and electrical compatibility.
Electrical checks and fuse considerations
If the CHMSL fails to illuminate after replacement, run through basic electrical checks to identify simple causes before replacing components.
- Locate the fuse box and check for a CHMSL, STOP, or Center High Mounted Stop Lamp fuse. Replace any blown fuse with the correct amperage as specified in the owner’s manual.
- Inspect the CHMSL wiring harness and connectors for corrosion, bent pins, or loose connections at the lamp and at the fuse panel.
- Look for water intrusion or condensation inside the light housing or trunk area that could cause intermittent operation.
- Test the light again after reassembly to verify persistent illumination and stability.
If issues persist, consider having a Hyundai technician or automotive electrician diagnose possible wiring faults or control-module involvement.
When to seek professional help
Replacing the third brake light is usually straightforward, but if you encounter persistent electrical problems, water leaks, or a non-serviceable LED module, professional assistance can prevent damage to the tailgate and electrical system.
Summary
For the 2018 Elantra, the third brake light may be bulb-based or LED-based depending on trim. Bulb-based units let you swap the bulb by removing rear hatch trim and the light housing, typically a quick and inexpensive fix. LED units generally require replacing the entire CHMSL assembly. Always follow safety steps, verify fuses and wiring, and consult a professional if you’re unsure about the type or compatibility of replacement parts. Keeping the CHMSL functioning is essential for visibility, safety, and compliance with regulations.