Circuit Description

How 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 disables the car from starting.

Battery voltage is supplied at all times through fuse 23 (in the under-hood fuse/relay box) to the Immobilizer-Keyless Control Unit and the gauge control module. With the ignition switch in ON (II) or START (III), the Immobilizer-Keyless Control Unit and the ECM/PCM receive battery voltage through fuse 2 (in the under-dash fuse/relay box).

If the proper ignition key is used, the Immobilizer-Keyless Control Unit sends a coded signal to the ECM/PCM and illuminates the immobilizer system indicator LED for 2 seconds. The coded signal informs the ECM/PCM that the proper ignition key is being used. The ECM/PCM grounds the PGM-FI Main Relay 2, energizing it to provide power to the fuel pump (DX, DX-G, LX, EX, Si). The PCM grounds the Injector control Module Relay, energizing it to provide power to the Fuel Pressure Regulator Shut-off Solenoid Valve and Fuel Tank Internal Solenoid Valve (GX). Following the first 2 seconds after the ignition switch is turned to ON (II) with the proper ignition key, the immobilizer system indicator LED turns off and the engine will run under normal operating conditions.

Normal operation
- When the ignition switch is turned ON and a programmed immobilizer code is identified, the immobilizer indicator comes on for 2 seconds and then goes out.
- The immobilizer system will allow the car to start normally.
- When the ignition switch is turned OFF, the immobilizer indicator does not come on. (Please note, this is different from previous systems.)

Immobilizer system detects a problem
- When the ignition switch is turned ON and a programmed immobilizer code is not identified, the immobilizer indicator comes on for 2 seconds and then blinks continuously.
- The immobilizer system results will vary depending on how quickly the key is turned. If the key is turned quickly from the OFF (0) position to the START (III) position,the car will start and run for approximately 1 second and shut off. If the key is turned to the ON (II) position, delayed there, and then turned to the START (III) position, the starter will turn the motor over, but it will not start.
- When the ignition switch is turned OFF, the immobilizer indicator blinks ten times. (Please note, this is different from previous systems.)