These instructions apply to the Audi A3 Mk3 (8V) 2012-2020.
For other models, please choose your vehicle here.
A flagging remote on your Audi A3 8V (2012–2020) — short range, a button that needs repeating, or no response — is almost always the fob’s coin cell rather than a fault in the car. The swap takes a few minutes, and the A3 lets you re-pair the remote at the driver’s door if it has lost sync. Here is the complete procedure, and the one job that still belongs to Audi.
Try the Battery First
The 8V A3 (Sportback, Saloon and Cabriolet) uses Audi’s switchblade key with a CR2032 cell. Because a weak cell is behind the vast majority of remote problems, fit a fresh one before suspecting anything deeper. The metal blade folds out to open the door, so a dead fob never locks you out.
Replacing the Fob Battery
- Pull the key blade out using the catch to expose the case seam.
- Carefully part the two halves of the fob with a small flat screwdriver.
- Press a button on the remote to discharge it, then lift out the old CR2032.
- Fit the new cell the same orientation as the original, touching only the edge.
- Reassemble, refit the blade, and check the buttons respond.
Re-synchronising the Remote
If the remote stays unresponsive after a new cell, re-register it at the door:
- Remove the door-handle lock cover on the driver’s side.
- Insert the blade into the exposed lock.
- Press unlock on the remote, then turn the key within one minute.
- The key re-registers — verify normal operation.
Lost Key or Adding a Spare
The above is for a key the A3 already knows. Coding a new key — replacing a lost one or adding a spare — involves the immobiliser and needs Audi dealer or specialist equipment. There is no owner button-sequence that pairs a fresh transponder.
If a New Cell and Resync Don’t Work
- Recheck polarity and the contacts — the usual culprits when a swap doesn’t take.
- Advanced-key (keyless) A3s use a comfort fob that still takes a CR2032 and opens the same way.
- Still nothing? A convenience-system or receiver fault may store a code you can look up on autodtcs.com.
Frequently Asked Questions
What battery does the A3 8V key fob use?
A CR2032 coin cell — confirm against the old one.
Do I need to recode the key after the battery change?
No. Coding is kept; only a remote that lost sync needs the door resync above.
Can I program a new Audi A3 key myself?
No — a new key must be coded to the immobiliser with Audi/VAG equipment.
Is the keyless “advanced key” fob different?
It opens the same way and uses the same CR2032; only the comfort features differ.
If the fob stopped after a battery disconnection, our A3 8V battery disconnect/reconnect guide covers the resync in context.
Independent guide — not affiliated with Audi. Always follow your official service manual and safety precautions. Read our full disclaimer.