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10C-8 Immobilizer Control System:
DTC P1621 Immobilizer Communication Line Error
Possible Cause and Trouble Area
Possible Cause
• Temporary error
• Related fuse(s) blown
• Poor connection at immobilizer control module
connector
• "BLK/WHT" wire open
• "BLK/ORN" wire open
• "YEL/BLK" wire open, short to ground circuit, short to
power circuit, or shorted to "YEL/RED" wire
• "YEL/RED" wire open, short to ground circuit, short to
power circuit, or shorted to "YEL/BLK" wire
• Immobilizer control module faulty
• ECM faulty
Troubleshooting
Step
1
Diagnostic Trouble Code (DTC) confirmation:
1) Clear DTC(s) referring to "Diagnostic Trouble Code
(DTC) Clearance: ".
2) Turn the ignition switch to OFF position.
3) Check if any DTC is detected referring to "Diagnostic
Trouble Code (DTC) Check: ".
Is DTC P1621 still detected?
2
Fuse check:
1) Check if any related fuse is blown.
Is any fuse blown?
3
Check for poor connection at immobilizer control
module:
1) Disconnect immobilizer control module connector "G24"
referring to "Immobilizer Control Module Removal and
Installation: ".
2) Check if wire connections are normal at immobilizer
assembly connector "G24".
Is each wire connection normal?
4
Check for poor connection at ECM:
1) Disconnect ECM connector "E23" referring to "Engine
Control Module (ECM) Removal and Installation: in
Section 1C".
2) Check if wire connections at "E23-13" and "E23-28" wire
terminals are normal.
Is each wire connection normal?
5
Check for open in "BLK/WHT" wire:
1) Connect immobilizer control module connector "G24"
referring to "Immobilizer Control Module Removal and
Installation: ".
2) With the ignition switch at ON position, check voltage
between "G24-1" wire terminal at immobilizer control
module and body ground.
Is voltage about 12 V?
Action
Trouble Area
• Related fuse(s)
• Connection at immobilizer control module
• "BLK/WHT" wire
• "BLK/ORN" wire
• "YEL/BLK" wire
• "YEL/RED" wire
• Immobilizer control module
• ECM
Yes
Go to Step 2.
Replace blown fuse(s)
with new one (s).
Go to Step 4.
Go to Step 5.
Go to Step 6.
S4RS0AA304029
No
The troubleshooting is
completed.
Go to Step 3.
Repair poor
connection(s).
Repair poor
connection(s).
Repair open in "BLK/
WHT" wire.
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