How the Circuit Works

How the Circuit Works
The immobilizer system is designed to prevent the car from being started without the owner's ignition key. It an attempt is made to start the car without the correct key, the immobilizer system will disable the car.

The immobilizer system consists of the immobilizer control unit, ignition key, immobilizer receiver, immobilizer indicator light., starter cut relay, powertrain control module (PCM), parking brake switch, and the A/T gear position switch.

The immobilizer control unit receives battery voltage through fuse 6 at all times. For '96-'98 models when the ignition switch is in ON (II) or START (III) and the gear selector is in neutral or park, the immobilizer control unit receives an "ignition on" signal through fuse 20 and sends power to the ignition key transponder through the immobilizer receiver. For '99-'04 model vehicles, when the ignition switch is in ON (II) or START (III), the PGM-FI main relay coils are energized. The contacts close, and with the gear selector in neutral or park, the immobilizer control unit receives an "ignition on" signal through fuse 6 and sends power to the ignition key transponder through the immobilizer receiver. The transponder then sends a coded signal back to the control unit through the receiver. If the signal is correct, the control unit energizes the starter cut relay and sends a "fuel enable" signal to the PCM. The immobilizer indicator light flashes a code to indicate that the correct key is inserted. If the ignition key signal is not correct, the immobilizer control unit disables the starter cut relay and does not send a "fuel enable" signal to the PCM. The immobilizer indicator light then flashes a code to indicate that an incorrect key is inserted.

The ignition key must be programmed to the immobilizer control unit with the special ignition switch key (learning key).