Where is the immobilizer located - 2000 Volkswagen Jetta TDI

The immobilizer stays active until you actually try to start. To start (and turn the immobilizer off) the key needs to be in the ignition, the code in the fob read by the security system and the ignition switched to start - this is when the immobilzer LED goes off.

If the car was unlocked and had the correct key the car would still not start unless the key was attached to the correct fob.

Question edited to remove abbreviations.

https://www.google.com/search?q=toyota+isis+immobilizer+module+location

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I'm led to believe by another source that this immobilizer ECU may be located on the firewall behind the HVAC case which would require removal of the entire dash assembly and discharging the A/C system and engine coolant system to also remove the entire HVAC case assembly.

It should be located under the dash on the driver's side. It will be wired into the ignition switch.

Anti-theft system problem , possibility ! Do you have a security light blinking ? Security Indicator
The security indicator is located in the clock on the top of the instrument panel. The light emitting diode (LED) displays the immobilizer system status. The immobilizer contains the LED driver hardware for direct connection of the LED.
Vehicle Theft Deterrent (VTD) Operation
The immobilizer system design prevents vehicle theft by interrupting the engine operation. The immobilizer system prevents the vehicle from starting. The engine operating functions interrupt if the immobilizer system does not recognize the transponder identification code of the ignition key. The immobilizer system and the content theft deterrent system do not interact. The system includes the following components:
?€¢
The ignition key

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The column-mounted theft deterrent module with integrated antenna

?€¢
The transponder

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The engine control module (ECM

in trunk, left side

what country
ISIS ?
not here. so cant help.
get your cars FSM from the dealer, and read that.
its all there, and is very complex.
he IMMO is married tot he PCM and BCM.
so.... lots of issues dealing with that.

get the FSM.

are you using a key copy, w/o a chip in it? if so, it will immobilize. if it's a new key "with" a chip, it needs to be programmed.

Sounds like starter, especially if it is clicking. However, i have run into problems where the aftermarket security was an issue because it disables the starter when actiated, try a starter first, if that doesnt work remove the aftermarket alrm/immobilizer and wire it back to stock.