Audi Key Fob Battery Replacement – Audi A4/S4/RS4 2005.5-2008 Model Years

If you’re anything like me, the battery died on your first key fob a long time ago, and then you switched to your second backup key fob and now its battery has run out too – so it’s well past time to change the batteries.

You could have the dealer do it, where I’ve heard estimates range between $80-150 per key…or you could do it yourself for about $5 in under 5 minutes. Needless to say, I took the later route, and I’m here to tell you it’s very easy to do – simply press in two tabs on the key, pop off the back cover, replace the battery, and then press the rear cover back into place. You’ll also need to re-program the key, which is as simple as turning the car on/off 5 times.

This article applies to any keys that look like the one pictured above, most notably the B7 platform Audi A4, S4 or RS4, which was produced from 2005.5-2008. Other Audi models from this date range also share the same key, and the instructions should apply to those models too (although reprogramming the key for your car may differ slightly), however I can’t confirm which other models this applies to.

Supplies Needed:

  1. 1 CR2032 Battery (per key fob) – I purchased a 5 pack on Amazon for $5 which allowed me to replace the batteries on both of my key fobs as well as have a few extras for down the road, but you really only need 1 per key.
  2. A small flat-head screwdriver – those for eyeglasses work great, but any screwdriver should be fine. A pen would probably work if you’re in a pinch, but be careful not to do anything that would leave a mark or print on the key.
Step 1 - Press in Tab Where Key collapses
Step 1 – Press in Tab Where Key collapses

Step 1 – Press in the tab located along the side of the battery where the key folds in using your small flat head screwdriver. You’ll want to press it hard enough that the back cover starts to pop out.

Step 2 - Press in Tab on bottom of key
Step 2 – Press in Tab on bottom of key

Step 2 – Press in the second tab, located on the bottom of the key. You’ll want to press hard enough that the rear cover is pretty much completely popped off, and then you can simply just remove the cover with your fingers.

Step 3 - Pop out back cover
Step 3 – Pop out back cover, replace battery

Step 3 – Replace the battery, making sure the positive side of the battery is facing up.

Step 4 – Pop the rear cover back on the key fob, which can be done just by pressing the key back together (no tools needed)

Step 5 – You will probably need to reprogram the key. To do this simply insert your key into the car’s ignition, then turn it on/off 5 times (do not start the car, just turn it to the ON position right before a full start). This will reprogram the key.


  • If you do not see a red light when you press lock/unlock on the key fob, either the battery is installed incorrectly, the battery is dead, or there is some other issue with your key fob (e.g. water damage) preventing it from sending a signal. Replace the battery and be sure to have the positive side of the batter facing outward, and then order a new key fob if that does not work.
  • If a red light appears when you hit lock/unlock on your key fob, but the doors do not lock/unlock, you need to reprogram your key to the car. The reprogramming process may vary by your specific model, so if you do not have a B7 platform Audi A4, S4 or RS4, try Googling the instructions for your specific car.

Nick Roshon

Nick has been an Audi owner and fanatic for the last 10 years, and started Nick's Car Blog in 2009 to share DIYs and pictures of his A4. Currently he drives a 2012 Audi TT-RS, and has previously owned a B7 S4, B7 A4, and an 82 Audi Coupe (GT) LeMons race car. In his day job, Nick is a digital marketer and lives in San Diego, CA, USA.


  1. In the owner’s manual it tells you to place a quarter under the backside lip under the key loop, then pry the back cover open using the key loop as the fulcrum. It worked easily for me.

  2. Do you by chance know how to get a replacement key without paying $150 bucks for it plus programming?

  3. You can find the key pretty cheap on eBay or sometimes in the classifieds, but you’ll still have to get it cut & programmed by the dealership unfortunately.

  4. Nick, I have an 02 a4 Quattro, having locked the car then not being able to get back in via the fob, I assumed it was the battery. I replaced the battery, then as according to the handbook locked & unlocked the car with key to re-sync. This was ineffective. After reading your post, I also tried the ignition on/off turn 5 times….still nothing. Any ideas?

  5. Yes….my second key works ok, the first one hasn’t been dropped or gotten wet….so I assumed it must’ve been battery. Just don’t want my spare to do the same. Thx for response anyway Nick.

  6. Tried this, but didn’t work, at first. Then, after the 5 on/off cycles described, pressed and held the unlock button for a few seconds while the car was on – that appeared to be the final step – 2008 A4 Cab.

  7. Nick I have an A4 Quattro estate 2005. The rear windscreen wiper motor has packed up. How easy is it to remove the tailgate interior trim so I can replace the motor

  8. Nick,
    You are a star, I found on other site, the instructions how to change the fob battery.
    I followed instructions and the little red light on the fob flashed, but did not lock / unlock.
    I checked my spare key did the same, now this key not work, so now x2 keys neither working.
    I found your web details with the little extra detail being “Step 5 – You will probably need to reprogram the key”
    I love you, now x2 fully working keys. YOU’RE THE MAN

  9. Nice writeup, but cant seem to get this to work for one of my keys. 06 a4. Fresh battery, lights up but no action on button push.

  10. Yeah i tried that too, no dice. Both ways. Few times over past few days. Think the chip is bad?

  11. Nick! i was just reading your article like it was my bed time story, and i ran downstairs to do the 5-time key recoding thingie and it worked just fine!
    now i can have happy dreams! hehe! thanks a bunch! goodnight!

    love from Egypt.

  12. Just replaced my key’s battery! Thank you for the DIY instructions. Very helpful and cheaper than anything Audi would have offered me.

  13. Nick where can I get a second key from without getting raped? my Avant only came with one…..
    any thoughts?

  14. Sorry, not too familiar with that thankfully – the issue is that even if you buy the key aftermarket, you need a dealership to cut it for you. There are very few options here…

  15. hi Nick.
    I have an Audi A4 2006. I have changed the battery on the remote key.. The red light turns on the key when hiting any buttons, but it doesnt open the car doors. The key doesnt however turn on the engine when used though.. any step by step help you can provide?

    thanx for help..

  16. I think you mean the key does turn on the engine, just not remote lock/unlock, right? If so, it sounds like it needs reprogrammed. Try sticking the key in the ignition and going from off to accessory on (not start the car, just turn the radio & accessories on) and do that on/off 7 times. It should do the trick…

  17. Hi Nick I have a 2008 audi a4. When i press the lock or unlock buttons, the red light doesn’t turn on, but when i put the key in the key place in the back seat, it starts blinking. Why is this? And just to be clear I’m talking about the key placement thingy in the rear seats.

  18. I have an S4,so it’s a little different than the pics shown above. I can get it apart, but where the heck is the battery? Haha

  19. Hi, thanks for sharing this. Both my keys have been flat for ages. I got 2 batteries and mini screwdrivers on ebay for under $10 delivered. I didnt even need to do the reprogramming trick. Audi’s replacement price is a blatant rort.
    Really prefer doing the one remote click to open just the driver’s door and hop straight in at night- seems safer and being able to get all the shopping out and not have to go and manually lock the driver’s door is life changing!!
    Thanks for taking the effort with this- appreciated! XD

  20. In order to reprogram the key there is also an another way. You just insert the key, turn it on (do not start the engine) press & hold the unlock button for 5-10 seconds, release the unlock button, then turn off, remove the key and your are done.

  21. I changed my battery and made sure the positive side was up, but my key fob still doesn’t blink red when I press a button. The key fob flashes when I use the key to open up the trunk, why is this? Thanks

  22. Thanks Nick. This worked great with my 2007 Audi A4. The key was still flashing red when I pushed the button, but the battery must have been too weak. The new battery worked. One note, the first time I programmed the key it didn’t work. The second time I programmed the key I turned the key (but not the motor) on for about a one second count and it worked. Also, I was able to pop the key open by just putting another key in the depression on the end of the key.

  23. Ok so how do you reprogram the battery to the key if your car is in the locked position and you can not stick your key in the ignition changed my old battery because it didn’t unlock my doors. Could someone help please

  24. Hi Nick my name is Brandie and I have a 2011 S4. Been having issues with my car. Comp told me that my battery on fob was low so I grabbed my other fob that had rarely been used. Still got that message ( I had both on me) I replaced both batteries and still get that message from time to time. Now my car has told me that I can’t lock my doors because my car is not in park. My computer says its in park though. My mechanic says my gearbox needs to be replaced but I don’t think that is the issue since my baby shifts like a dream. Do you think I could be having these problems because I have not reprogrammed / synced my fobs? Thanks for your time. Brandie

  25. I am not sure if it is your keys per se, or something with the locking system. I agree it doesn’t sound like a bad gearbox just because it won’t lock but otherwise drives fine, sounds more like an electrical glitch.

  26. Hey Nick,
    I replaced thermostat in 2007 Audi A4 B7, I unplugged negative cable from the battery. After I put everything together, radio/clock got reset, everything else works except for remote controls on both of my keys. I followed Audizine tutorial on reprogramming the keys and I tried valant key or fob keys in ignition and programming the other – the car reacts as if everything went fine (lights blink, then when I press unlock on fob the doors unlock) but the moment I pull out valant key fobs don’t work anymore…

    I checked owner’s manual – it tells that to synchronize a fob you have to get in the car, press unlock one time on a fob, put the fob in ignition and turn the motor on, then off, pull out the key and press again unlock – Didn’t work, lol, even though I can clearly hear a clicking noise as if the car performed some registering operation.

    One more thing is that since none of my remote controls work as of now, when I lock the car mechanically with fobs or valant key, the alarm is armed and red diode flashes, but after 20-40 seconds the alarm starts to ring – just the sound, not the emergency lights…efficiently preventing me from locking my own car..

    I will try the 5x on/off tomorrow

  27. Hi Nick
    I have a 2004 a4 1.8t(B6) I have a problem with locking/unlocking the car with the remote key. sometimes it does and other times it doesn’t. if you manually open it with the key then its fine. look forward to your suggestion/fix

    regards and thanks for any help you can afford

  28. Hi Vinesh – hard to say exactly, it could be that the battery is going bad so the signal is pretty weak. You might want to try replacing the battery and see if that helps.

  29. Your instructions were so simple and easy to follow that I had my second key working in two minutes.
    Love your work!

    A4 B7 Avant

  30. Just got the battery replaced and FOB reprogrammed based on your instructions. Very helpful indeed, thanks!

  31. 2007 A4 – A fob-less spare key starts the car and immediately dies. Fobbed key works fine. Fob-less key does have a transponder inside but no battery or electronics (just the tiny glass tube). Fob-less key unlocks the doors etc. just fine. Tried the multi on-off ignition trick and nothing. The fob-less doesn’t work if the fobbed key is next to it. Any ideas?

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