Suzuki SY413 Service Manual page 2358

8G-24 IMMOBILIZER CONTROL SYSTEM (IF EQUIPPED)
DTC21 ECM/IMMOBILIZER CONTROL MODULE CODE NOT MATCHED
(IMMOBILIZER CONTROL MODULE SIDE)
DTC81 ECM/IMMOBILIZER CONTROL MODULE CODE NOT MATCHED (ECM/PCM SIDE)
(P1623)
DTC84 ECM/IMMOBILIZER CONTROL MODULE CODE NOT REGISTERED
(P1620)
DESCRIPTION:
D DTC21
Immobilizer Control Module checks if ECM/Immobilizer Control Module code transmitted from ECM/PCM and
that registered in Immobilizer Control Module match when ignition switch is ON. If they do not, this DTC is set.
D DTC81 (P1623)
ECM/PCM checks if ECM/Immobilizer Control Module code transmitted from Immobilizer Control Module and
that registered in ECM/PCM match when ignition switch is ON. If they do not, this DTC is set.
D DTC84 (P1620)
ECM/PCM checks if code transmitted from Immobilizer Control Module and that registered in ECM/PCM match
when ignition switch is ON. If there is no ECM/Immobilizer Control Module code registered in ECM/PCM, this
DTC is set.
INSPECTION:
Perform procedure described in "Procedure after ECM/PCM Replacement" section.