Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

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HOMESERVICE MANUALSSUZUKI2013SX4 CROSSOVER, AUTOMATIC CVT TRANSREPAIR AND DIAGNOSISBODY & FRAMEDOOR LOCKSIMMOBILIZER CONTROL SYSTEMDIAGNOSTIC INFORMATION AND PROCEDURESDTC P1621: IMMOBILIZER COMMUNICATION LINE ERRORTROUBLESHOOTING

2013 Suzuki SX4 Crossover, Automatic CVT Trans

DTC P1621: Immobilizer Communication Line Error: Troubleshooting

2013 Suzuki SX4 Crossover, Automatic CVT TransSECTION Troubleshooting

P1621: TROUBLESHOOTING CHART

Step	Action	YES	NO
1	Was "Immobilizer Control System Check" performed?	Go to Step 2.	Go to IMMOBILIZER CONTROL SYSTEM CHECK .
2	Fuse check Check fuse for ICM circuit. Is fuse in good condition?	Go to Step 3.	Replace blown fuse(s) and then, check for short to power circuit.
3	Voltage check at power and ground terminal Check power and ground terminal voltage of ICM connector referring to INSPECTION OF ICM AND ITS CIRCUIT . Is each terminal voltage in good condition?	Go to Step 4.	Repair circuit.
4	ICM and ECM connector check With the ignition switch at OFF position, check intermittent and poor connection of ICM connector and ECM connectors referring to INTERMITTENT AND POOR CONNECTION INSPECTION . Is each connector in good condition?	Go to Step 5.	Repair poor connection.
5	Communication circuit check between ICM and ECM Check for open, short and high resistance in serial communication and clock circuit between ICM and ECM. Is each communication circuit in good condition?	Substitute a known-good ICM and recheck. If DTC P1621 is still detected, substitute a known good ECM and recheck.	Repair circuit.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.