On older Passats, the immobilizer module is built into the back of the instrument cluster. Solder joints inside the cluster often crack.
Before attempting fixes, confirm the immobilizer is the actual issue. immobilizer active vw passat
: Replacing the key fob battery usually won't fix this specific error, as the immobilizer chip is passive and powered by the antenna's magnetic field, not the fob's battery. Common Causes for "Immobilizer Active" On older Passats, the immobilizer module is built
The wiring harness that runs from the body into the driver's door often frays and breaks inside the rubber boot. On older Passats
: A small RFID transponder chip inside your key communicates with an antenna (reader coil) located around the ignition cylinder.