Antitheft and Alarm Systems: Description and Operation

THEFT DETERRENT / KEYLESS ENTRY: ENGINE IMMOBILISER SYSTEM: SYSTEM DIAGRAM






1. ENGINE IMMOBILISER SYSTEM DESCRIPTION

The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses the transponder key ECU assembly that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ECU sends a signal to the ECM to prohibit fuel delivery and ignition, effectively disabling the engine.

2. FUNCTION OF MAIN COMPONENTS





3. SYSTEM FUNCTION

(a) When the transponder key ECU assembly detects that the key unlock warning switch is ON, the ECU provides current to the transponder key coil and produces an electric wave. A transponder chip in the key grip receives the electric wave. Upon receiving the electric wave, the transponder chip outputs a key ID code signal. The transponder key coil receives this signal, which is amplified by the transponder key amplifier, and the signal is transmitted to the ECU.

The ECU matches the key's ID code with the vehicle's ID code, which was previously registered in the ECU, and communicates the results to the ECM.

After the identification results show that the key's ID code matches the vehicle's ID code and the ECU has confirmed their match: 1) the immobiliser system does not immobilise the engine and the engine starting controls (fuel injection control and ignition control) enter standby mode; and 2) the ECU transmits a security indicator off signal to the clock. Then, the clock turns off the security indicator light.

(b) The security indicator pattern is as shown below (when changing from immobiliser set status to unset status):