How to Replace the Key Fob Battery in a Volvo S40

1. Place the remote key with the keypad downward and pry open the cover with a small slotted screwdriver.
2. Remove the cover.
3. Note how the + and – sides of the battery are positioned on the inside of the cover.
4. Pry out the old battery and put in the new one, avoiding touching the battery and its contact surfaces with your fingers.
5. Press the cover back into place.

• Battery type is CR 2450, 3V.
• Avoid touching the electrical circuitry in the other half of the remote key.
• A weak battery shows KEY BATTERY LOW VOLTAGE in the information display.

Source: 2011 Volvo S40 owner's manual, PDF page 124. 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.