How to Replace the Key Fob Battery in a Cadillac CT4

1. Press the button on the side of the remote key and pull out the mechanical key.
2. Use the mechanical key blade in the slot to pry off the battery cover by hand.
3. Pull the tab to remove the seal and reach the battery.
4. Remove the old battery without using a metal object.
5. Insert a new CR2450 Lithium or equivalent battery with the positive side toward the back cover.
6. Set the seal back into the groove, snap the cover on, and reinsert the mechanical key.

• Replace the battery when the DIC displays REPLACE BATTERY IN KEY.
• Do not touch the circuitry, and reassemble properly so the key stays sealed against liquids.
• Never pull the mechanical key out without pressing the button.

Source: 2026 Cadillac CT4 owner's manual, PDF pages 13, 14. 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.