Reset immobilizer VW Passat Saloon (3C2)

Try the 10-15 minute key-on reset first! Turn key to ON (not start), leave it there for 10-15 min, then turn off and try starting. Worked for me when my Golf had same issue after battery swap.

I had this exact problem with my 2006 Passat TDI! Battery died over winter, new battery in and nothing. Turned out the immobilizer just needed relearn - tried the key-on method 3 times in a row and it finally fired up.

Make sure you're using the original key with working transponder chip. My neighbor had this, turned out he was trying with the spare key that had a dead chip inside.

@user_81143 Check if your dashboard shows the immobilizer light flashing. If it's solid or flashing fast, the system isn't recognizing your key. Could be the key fob or the immobilizer module itself.

my brother's 2008 Passat had this and the simple resets didn't work at all. Ended up needing VCDS scan tool to clear the immobilizer codes and reprogram. Cost him about $200 at independent shop.

@jack.t Yeah but sometimes just disconnecting battery for 30 min and reconnecting helps too. Touching the cables together to discharge any residual power before reconnecting.

@OD23 That's what I was gonna say... if the basic resets fail, it's usually ECU issue. Friend had his Passat ECU sent off for immobilizer delete, around $160 and got it working again.

Before spending money, definitely try all your keys if you have spares! My sister's Jetta started right up with the second key after the first one wouldn't work post-battery change.

@user_81143 Also double check your key fob battery - even if the physical key turns, the transponder needs power to communicate with immobilizer. Replace that little battery first, it's like 2 euros.

Worst case scenario the ECU itself got corrupted during battery failure. I've read about people having to get ECU reprogrammed at dealer or specialist with proper diagnostic tools like VCDS - can run $100-300 depending where you go.

@Charlie 🍫 Wait so disconnect battery, touch cables together for how long exactly? 30 seconds or 30 minutes? Seen different info on this.

@Emily.B.Online I did 30 seconds, then waited a full minute before reconnecting. Just drains any capacitors in the system. Might help reset the immobilizer sync.