Immobilizer Control System: 10C-12
DTC P1621: Immobilizer Communication Line Error
S7RS0BA304012
Detecting Condition and Trouble Area
DTC Confirmation Procedure
1) Ignition switch turn to ON position.
2) Check DTC for ECM.
Troubleshooting
3 DTC check of BCM
Check BCM for DTC referring to “DTC Check in Section
10B”.
Is DTC U1073, U1100 and/or U1144 detected?
Go to applicable DTC
diag. flow.
Go to Step 4.
4 Control module connector check
1) Check connection of connectors of all control modules
communicating by means of CAN.
2) Recheck DTC.
Is DTC P1618 detected?
Go to Step 5. Intermittent trouble.
Check for intermittent
referring to “Intermittent
and Poor Connection
Inspection in Section
00”.
5 CAN communication circuit check
1) Turn ignition switch to OFF position.
2) Disconnect connectors of all control modules
communicating by means of CAN.
3) Check CAN communication circuit between control
modules for open, short and high resistance.
Is each CAN communication circuit in good condition?
Go to Step 6. Repair circuit.
6 Keyless start control module power and ground circuit
check
Check for keyless start control module power and ground
circuit referring to “Keyless Start Control Module Power and
Ground Circuit Check in Section 10E”.
Are they in good condition?
Substitute a known-
good keyless start
control module and
recheck.
Repair keyless start
control module power
and/or ground circuits.
Step Action Yes No
Detecting Condition Trouble Area
Communication error between ICM and ECM is detected
by ECM.
• Related fuse(s)
• Circuit between ICM and ECM
•ICM
•ECM
Step Action Yes No
1 Was “Immobilizer Control System Check” performed? Go to Step 2. Go to “Immobilizer
Control System Check”.
2 Fuse check
1) Check fuse for ICM circuit.
Is fuse in good condition?
Go to Step 3. Replace fuse and check
for short to power and
ground circuit.
3 Voltage check at ICM power and ground terminal
1) Check power and ground terminal voltage of ICM
connector referring to “Inspection of Immobilizer Control
Module (ICM) and Its Circuit”.
Is each terminal voltage in good condition?
Go to Step 4. Repair circuit.
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