Hint:

How to proceed with troubleshooting
Terminals of ecuEngine immobiliser system malfunction
Description
This dtc is output when one of the following occurs: 1) the ecm detects
errors in its own
communications with the transponder key ecu; 2) the ecm detects errors in the
communication lines; or
3) the ecu communication id between the transponder key ecu and ecm is different
an ...
Reassembly
Caution:
Wear protective gloves. Sharp areas on the seat frame
(with adjuster) may injure your hands.
Hint:
Use the same procedures for the rh side and lh side.
The procedures listed below are for the lh side.
Install occupant classification ecu (for
driver side) (see page rs-394)
...
If a warning light turns on or
a warning buzzer sounds
Calmly perform the following actions if any of the warning
lights comes on or flashes. If a light comes on or flashes, but
then goes off, this does not necessarily indicate a malfunction
in the system. However, if this continues to occur, have
the vehicle inspected by your Toyota dealer.
Actions to ...