Hi, can anyone please tell me how to resynch the key fob after a battery change, for a 2018 A6.

I had the replace key battery replace warning, which I've done but the fob won't now un/lock the car. I can start the car by placing it on the key sensor.

Any suggestions welcome, thank you.

Try leaving the key in the ignition for 5 or so minutes, fixed mine this way. Also check the battery polarity you could have put it in the wrong way.

18 minutes ago, Serrebrro said:

Try leaving the key in the ignition for 5 or so minutes, fixed mine this way. Also check the battery polarity you could have put it in the wrong way.

Its a keyless start/stop system, so no ignition unfortunately, just a wireless connection for the fob when the battery isnt working. Will check the battery though - fairly sure its correct but could be user error. Thank you

I have the same issue. 2019 c8 A6. I can get in by using the physical key, then re sync it by placing it on the wireless synching point (whilst the alarm is going off) and then it starts, alarm stops howling and all is good. It’ll then be fine for a day or so and then it seems to ‘forget’ it’s key again. If anyone has managed to solve this problem, any help would be greatly appreciated!

Hi Gareth,

just asking to see if you got to the bottom of this issue all be it more than three years plus later? I have a 2021 C8 A6 with exactly the same issue.

Many thanks 

Mike 

On 1/28/2026 at 1:58 PM, Mike Laird said:

Hi Gareth,

just asking to see if you got to the bottom of this issue all be it more than three years plus later? I have a 2021 C8 A6 with exactly the same issue.

Many thanks 

Mike 

Have you tried the spare key to at least rule out key issue? 

On 1/28/2026 at 1:58 PM, Mike Laird said:

Hi Gareth,

just asking to see if you got to the bottom of this issue all be it more than three years plus later? I have a 2021 C8 A6 with exactly the same issue.

Many thanks 

Mike 

On 1/30/2026 at 10:32 AM, Steve Q said:

Have you tried the spare key to at least rule out key issue? 

I've got the same issue, and now I'm praying that the battery on the spare key will last forever.

Well if the spare key is the same then that makes me think it's an issue with the car.

On 3/25/2026 at 5:15 PM, Steve Q said:

Well if the spare key is the same then that makes me think it's an issue with the car.

Can't see how that can be, as it doesn't open any doors, but it starts the car.

Could it be an issue with the driver's door module? As this controls the rest of the door modules I believe.