Audi A4 key fob battery
13 of the 29 model years listed for the Audi A4 have a proven battery. The most common answer is CR2032. Rows below run oldest to newest; a year can appear twice when the car came with more than one kind of key.
- 1996-1997Unknown
Not confirmed yet
- 1998-2003Key-head remote
CR2032
FCC ID MYT8Z0837231Two sites agree: uhs-hardware.com and americankeysupply.com (checked Nov 1, 2026)
Find CR2032 on Amazon - 2004-2005Unknown
Not confirmed yet
- 2006-2010Key-head remote
Not confirmed yet
- 2009-2015Smart key
CR2032
FCC ID IYZFBSB802Two sites agree: uhs-hardware.com and bestkeysupply.com (checked Nov 1, 2026)
Find CR2032 on Amazon - 2016-2019Unknown
Not confirmed yet
- 2020Smart key
Not confirmed yet
- 2021-2024Smart key
Not confirmed yet
Changing the battery
Key with remote in the head
- This type has the buttons built into the key head. The cell is inside that head, between two clipped halves.
- Work a thin flat tool into the seam near the blade and twist; go round slowly if it does not open at once.
- Inside you may find a small circuit board in a tray. Lift the board out if the cell is underneath, swap the cell with the same side up, and refit the board.
- Press the head together until it clicks and test the buttons. The transponder chip that lets the car start is separate from the battery, so starting should not change.
A CR2032 is 20 mm across and 3.2 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.
Smart key (push-button start)
- Find the small release on the edge or back of the fob and hold it while you pull out the metal emergency key.
- Use the slot where the metal key sat. Twist, do not lever hard, and work along the seam until the halves separate.
- Before you take the old cell out, look at its face. Put the new cell in with the same side showing, and avoid touching both faces at once.
- Reassemble, refit the emergency key, and check that the car sees the fob when you press start.
A CR2032 is 20 mm across and 3.2 mm thick. CR2032, CR2025 and CR2016 share the same width but not the same thickness, so a swap between them can leave a loose contact or a case that will not close.
Keep spare coin cells away from small children. A swallowed coin cell can burn the throat within hours; if it happens, go to an emergency room at once.