These instructions apply to the Volvo S40 Mk2 (544) 2004-2012.
For other models, please choose your vehicle here.
When the S40’s remote only works up close, or the dash warns of a low key battery, the fix is a fresh CR2032 coin cell you can fit in a couple of minutes. The remote keeps its coding — you are only swapping the battery.
Replace the S40 key fob battery
- Slide the metal emergency key blade out of the remote (this is often what holds the case together).
- Remove the small screw(s) and gently prise the two halves of the case apart.
- Lift out the old CR2032 coin cell.
- Fit the new cell the same way up (+ side as it came out), handling it by the edges — do not touch the flat faces or the contacts.
- Clip the case back together, refit the screw(s) and slide the key blade home.
Programming a brand-new remote needs Volvo diagnostic equipment, but a battery change like this needs nothing more than the coin cell.
Frequently asked questions
Which battery does the S40 remote use?
A single CR2032 3 V lithium coin cell, sold in any supermarket. Buy a fresh one rather than using a loose cell from a drawer.
The remote still will not work after a new battery — why?
Check the cell is the right way up and seated firmly, and that you did not touch the faces. If it still fails, the remote may need re-syncing at a dealer, but a flat cell is by far the most common cause.
Can I still get in if the remote is dead?
Yes — the metal emergency blade in the remote unlocks the driver’s door; use it and then start the car as normal.
If a key or immobiliser warning appears on the dash, you can check the code on autodtcs.com.
Independent guide — not affiliated with Volvo. Always follow your official service manual and safety precautions. Read our full disclaimer.