The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu 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.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then 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 then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingTorque converter and drive plate
Inspection
Inspect torque converter clutch assembly
Inspect the one-way clutch.
Install sst to the inner race of the one-way
clutch.
Sst 09350-32014 (09351-32010)
Set sst so that it fits in the notch of the
converter hub and in the outer race of the oneway
clutch.
...
Diagnostic trouble code chart
If a dtc is displayed during the dtc check, check the circuit
listed in the table below and proceed to the page given.
Hint:
*1: "Comes on" means the malfunction indicator lamp
(mil) illuminates.
*2: "Dtc stored" means the ecm memorizes the
malfunction code if the ecm ...
On-vehicle inspection
Check battery condition
Notice:
If the battery is weak or if the engine is difficult to
start, perform the following procedures.
Check the battery for damage and deformation. If
severe damage, deformation or leakage is found,
replace the battery.
Check the electrolyte quantity of e ...