Toyota Tundra Service Manual: System Description

SYSTEM DESCRIPTION

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 ID codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the transponder key ECU assembly sends a signal to the ECM to prohibit fuel delivery and ignition, effectively disabling the engine.

FUNCTION OF MAIN COMPONENTS

Component

Outline

Transponder key ECU assembly

  • When a key is inserted into the ignition key cylinder, the transponder key ECU assembly checks if the key ID code received from the transponder key coil and registered key ID code match.
  • When the engine is started, the transponder key ECU assembly checks if the engine ID codes stored in the ECM and transponder key ECU assembly match.

Transponder key coil

When a key is inserted into the ignition key cylinder, the transponder key amplifier receives the key ID code from the transponder chip in the key grip and outputs it to the transponder key ECU assembly.

ECM

The ECM receives key ID code verification results from the transponder key ECU assembly. The ECM also verifies the ECUs. Then judgment of whether to immobilise the engine is made.

Unlock warning switch assembly

The unlock warning switch assembly detects if the key is in the ignition key cylinder and outputs the result to the transponder key ECU assembly.

SYSTEM FUNCTION

(a) When the transponder key ECU assembly detects that the unlock warning switch assembly is on, the transponder key ECU assembly applies current to the transponder key coil and produces a magnetic field around the antenna coil. A transponder chip in the key grip outputs a key ID code signal using electromotive force generated by the magnetic field. The transponder key coil receives the signal and sends it to the transponder key ECU assembly. The transponder key ECU assembly checks if the key ID code received from the transponder key coil matches the registered key ID code.

When the engine is started, the ECM communicates with the transponder key ECU assembly and checks the key verification result. In addition, the ECM checks if the engine ID codes stored in the transponder key ECU assembly and ECM match. If they do not match, the ECM prohibits engine start.

    Security Indicator Light Does not Blink

    System Diagram

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