These instructions apply to the Audi A4 Mk5 (B9/8W) 2015-Present. For other models, please choose your vehicle here.
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Short range or a “key battery low” message on your Audi A4 (B9/8W, 2015–present) almost always means a tired coin cell. The A4 key uses one CR2032 and you can swap it in a couple of minutes.
What You Need
One CR2032 3 V coin cell — the standard Audi key battery.
Swapping the Cell
- Slide out the emergency key blade using the release catch.
- Use a coin in the slot to lift off the button-cell cover.
- Lift out the old CR2032, noting which way it faces.
- Fit the new cell positive (+) side up and refit the cover.
- Slide the blade home.
Check the lock and unlock from a few paces.
If It’s Still Dead
- You can still start it — hold the key to the start button as you press; the car reads the chip directly.
- Lock by hand with the blade in the driver’s door (behind a small cap).
Frequently Asked Questions
What battery does the Audi A4 key take?
A single CR2032 3 V coin cell, positive side up.
Reprogramming needed after the swap?
No — the key re-links the moment it has power.
How do I open the A4 key?
Remove the emergency blade, then lift the cell cover with a coin.
Keyless start still failing?
Hold the key against the start button while pressing it.
No-start with a dash light? Check the code on autodtcs.com. If the car’s flat, see our A4 battery guide.
Disclaimer: The information on this page is provided for general guidance only. Always follow your official service manual and safety precautions when working on your vehicle. We are not responsible for errors, omissions, or any damage resulting from the use of this information.
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