Fixed car fab sync issue 2015 Cupra

[BlackThunder]

So my fob stopped working after changing the battery recently. The battery was only low but when I put the new battery in and it didn't work at all. I decided to put the old battery back in and to my surprise it still didn't work! Thinking there was a particular technique to changing it, I gave it to the Seat dealer on my last service. They changed the battery and it still didn't work. It was my spare fob so wasn't massively concerned but when my main key battery indicated as low on the car display recently, I started to worry. I called Seat and asked if there was a technique to changing it and they said no, just swap with the new battery in my old fob. I asked how much it would cost to fix my old fob and they said £82 to diagnose it or £76 to reprogram it! Ouch, off to the forums I went!

Okay so long story short, swapped the battery and it worked. Checked forums for a fix for my old fob and couldn't find anything. I found a way to resync it in the manual and after 2 mins it worked fine.

Remove the key cover on the door handle, with the door unlocked, press lock on the fob then lock the car manually with the key (within 1 min). Then (and I had removed the key from the door) press unlock, insert ket and manually unlock. Key was resynced and now works fine.

Why Seat dealer couldn't do this and wanted to charge me to diagnose, we will leave for another thread!

Anyway, hope this helps a few of you that are struggling. The manual did say the key can become unsynced if the Button is pressed multiple times when out of reach of your car, and obviously in some occasions when the battery is changed, maybe by inadvertently pressing the buttons when doing it.

 

[Syphon]

Thanks for sharing. Potential resource guide for others ? @Lozzy15

 

[black_sheep]

If you look at the other VAG MQB platform marques, then there is a key fob battery change procedure. I can’t find the equivalent in the Leon workshop manuals (in the guide sections).

However, when you remove the battery, you are supposed to press one of the fob buttons prior to inserting the new battery. This is supposed to calibrate the key to acknowledge the new battery. Even though the image is for the previous style key, the Mk3 Octavia has the same key as Mk3 Leon.

 

[Cuprabenwytm]

I just changed mine, it had a varta in amd replaced it with somet from timpsons, charged me a 5a robbing g t**t, anyways i put the plus to the opposite side of the blade and chaged the battery while sat in the car and it worked great, thought i was goi g to have to reprogram it bit nope buzzing

 

[RUM4MO]

I always found that VW Group only ever fitted Panasonic brand of batteries in these fobs, well from 2000 until mid 2019 anyway.

I'm not in any way knocking any of the suggestions given in this thread, I'll save them for possible future use, but so far (dangerous talk) I've never ever had any issues when replacing key fob batteries, okay all but one fob did not have a battery that was failing to work, or was "giving out warnings", 2 X 2000 VW Passat 4Motion and 2 X 2002 VW Polo 1.4 16V both had the same or same looking fob as the Octavia in the picture above, 2 X 2011 Audi S4 and 2 X 2015 VW Polo 1.2TSI, obviously with newer types/profiles of keys, and finally 1 X 2019 SEAT Leon Cupra - it was the only car maybe capable of reporting "low fob battery".
It was always, get organised with "how to open up this type of fob" get tools and new battery - open fob up and immediately fit new battery, close fob and test key for correct operation.

The random single key pad press - maybe that always did happen accidentally! My plan with non-kessy keys is always to replace the batteries early, in the first pair of cars that meant at roughly 8 years from new and with this second pair at roughly 8 years and roughly 6 years.