How to Replace the Key Fob Battery in a GMC Sierra 2500HD/3500HD

1. Press the button on the side of the remote key near the bottom 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 seal's tab to 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 facing up.
6. Set the seal back in the groove, snap the battery cover on, and reinsert the mechanical key.

• Replace the battery soon when the DIC displays REPLACE BATTERY IN REMOTE KEY.
• Reassemble properly so the remote key stays sealed against liquids.

Source: 2026 GMC Sierra 2500HD/3500HD owner's manual, PDF pages 20, 21. 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.