Circuit Description
Immobilizer SystemHow the Circuit Works
The immobilizer system is designed to prevent the car from being started without the owner's ignition key. If an attempt is made to start the car with any other key, the immobilizer system will disable the car's fuel supply system.
The immobilizer system consists of the ignition key, immobilizer control unit-receiver, immobilizer system indicator, PGM-FI main relays, fuel pump, and the PCM.
Battery voltage is supplied at all times through fuse 13 to the immobilizer control unit-receiver. With the ignition switch in ON (II) or START (III), the immobilizer control unit-receiver and the PCM receive an "ignition on" signal through fuse 1 (in the driver's under-dash fuse/relay box) and the PGM-FI main relay 2.
The ignition key transponder examines the ignition key, then sends a coded signal back to the PCM through the immobilizer control unit-receiver. If the ignition key signal is correct, the PCM will enable the car's fuel supply system by energizing the PGM-FI main relay 2. The immobilizer system indicator flashes a code to indicate that a correct ignition key has been inserted. If the ignition key signal is not correct, the PCM will not energize the PGM-FI main relay 2, which will not enable the car's fuel supply system. The immobilizer system indicator then flashes a code to indicate that an incorrect ignition key has been inserted.