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 troubleshootingRemoval
Disconnect cable from negative battery
terminal
Caution:
Wait at least 90 seconds after disconnecting the
cable from the negative (-) battery terminal to
prevent airbag and seat belt pretensioner activation.
Remove front fender liner lh
Remove front fender liner lh
Remove the ...
If the vehicle battery is discharged
The following procedures
may be used to start the
engine if the vehicle's battery
is discharged.
You can also call your
Toyota dealer or a qualified
repair shop.
Restarting the engine
If you have a set of jumper (or
booster) cables and a second
vehicle with a 12-volt battery,
you can jump start you ...
Replacement
Replace timing chain cover oil seal
Hint:
There are 2 methods to replace the oil seal.
If the timing chain cover is removed from the
cylinder block:
Using a screwdriver and hammer, tap out the
oil seal.
Apply multi-purpose grease to the lip of a new
oil seal.
Notice:
...