Toyota 4Runner: System Description

Toyota 4Runner Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Engine Immobiliser System(w/o Smart Key System) / System Description

SYSTEM DESCRIPTION

1. ENGINE IMMOBILISER SYSTEM DESCRIPTION

(a) The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a 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 COMPONENT

Component	Outline
Transponder key amplifier	When the key is inserted into the ignition key cylinder, the antenna coil receives the key code. Then the amplifier amplifies the ID code and outputs it to the transponder key ECU assembly.
Unlock warning switch assembly	Detects whether the key is in the ignition key cylinder and outputs the results to the transponder key ECU assembly.
Security indicator light	Depending on the operation of the transponder key ECU assembly, the security indicator light turns off or starts blinking.
Transponder key ECU assembly	Checks the ID code received from the transponder key amplifier and if the results match, an EFI operation permission signal is sent through the SFI communication.
ECM	Through the SFI communication, the ECM receives the ID verification results from the transponder key ECU assembly. The ECM also verifies the ECUs. Then the judgment of whether or not to disable engine is made.

3. SYSTEM FUNCTION

(a) When the transponder key ECU assembly detects that the unlock warning switch assembly is on, the transponder key ECU assembly provides current to the antenna coil and produces a weak 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, the signal is amplified by the transponder key amplifier and the signal is transmitted to the transponder key ECU assembly.

(b) The transponder key ECU assembly matches the key ID code with the vehicle ID code, which was previously registered in the transponder key ECU assembly, and communicates the results to the ECM. After the identification results show that the key ID code matches the vehicle ID code and the transponder key ECU assembly has confirmed their match: 1) the engine immobiliser system is canceled and the engine starting controls (fuel injection control and ignition control) enter standby mode; and 2) the transponder key ECU assembly transmits a security indicator light signal that communicates "indicator off" to the combination meter assembly (security indicator light) and the security indicator light turns off.

(c) The security indicator light pattern is as shown below (when changing from the immobiliser set state to the unset state).

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