Dtc P1621: Immobilizer Communication Line Error - Suzuki Swift Sport 2004 Service & Repair Manual

Step
3 DTC check of BCM
Check BCM for DTC referring to "DTC Check in Section
10B".
Is DTC U1073, U1100 and/or U1144 detected?
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?
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?
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?

DTC P1621: Immobilizer Communication Line Error

Detecting Condition and Trouble Area
Detecting Condition
Communication error between ICM and ECM is detected
by ECM.
DTC Confirmation Procedure
1) Ignition switch turn to ON position.
2) Check DTC for ECM.
Troubleshooting
Step
1 Was "Immobilizer Control System Check" performed?
2 Fuse check
1) Check fuse for ICM circuit.
Is fuse in good condition?
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?
Action
Action
Immobilizer Control System:
Yes
Go to applicable DTC
diag. flow.
Go to Step 5.
Go to Step 6.
Substitute a known-
good keyless start
control module and
recheck.
Trouble Area
• Related fuse(s)
• Circuit between ICM and ECM
• ICM
• ECM
Yes
Go to Step 2.
Go to Step 3.
Go to Step 4.
10C-12
No
Go to Step 4.
Intermittent trouble.
Check for intermittent
referring to "Intermittent
and Poor Connection
Inspection in Section
00".
Repair circuit.
Repair keyless start
control module power
and/or ground circuits.
S7RS0BA304012
No
Go to "Immobilizer
Control System Check".
Replace fuse and check
for short to power and
ground circuit.
Repair circuit.