How to Replace the Key Fob Battery in a Hyundai Sonata

Steps from the 2026 Hyundai Sonata owner's manual (smart key).

Insert a slim tool into the slot (1) and gently pry open the rear cover.
Take out the old battery.
Insert a new CR2450 battery, making sure its position is correct.
Reinstall the rear cover of the smart key.

Battery type: CR2450.
An improperly positioned battery may discharge and cause smart key failure.
A "Low key battery" cluster message may appear when the Engine Start/Stop button is pressed to OFF.

Source: 2026 Hyundai Sonata owner's manual, PDF pages 137, 118. Steps are summarized in our own words (AI-assisted, checked against the cited pages 2026-10-18). Other model years can differ; your manual has the final word.

Confirm with your own manual, dipstick or door-jamb label.
Report a problem with this page →