Suzuki Grand Vitara JB416 / JB420. Manual - part 421

10C-14 Immobilizer Control System: 

Troubleshooting

Step

Action

Yes

No

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 P1618 still detected?

Go to Step 2.

The troubleshooting is 
completed.

2

Diagnostic Trouble Code (DTC) check in ECM

Is any DTC other than P1618 detected in Step 1?

Perform the 
troubleshooting 
referring to the 
corresponding 
flowchart.

Go to Step 3.

3

Poor connection check at ECM, ABS and keyless start 
control module connectors
1) With the ignition key at OFF position, check each 

connector and wire terminal at ECM, ABS and keyless 
control module for secure connection.

Is each connector and wire terminal connected securely?

Go to Step 4.

Repair poor 
connection(s).

4

Check for open and high resistance in CAN 
communication wire circuits between ABS and keyless 
start control module
1) Disconnect connector “E03” from ABS referring to “ABS 

Hydraulic Unit / Control Module Assembly Removal and 
Installation in Section 4E”.

2) Disconnect connector “G42” from keyless start control 

module referring to “Keyless start control module 
Removal and Installation in Section 10E”.

3) Measure resistance at the following wire terminals.

• Between “E03-12” wire terminal at ABS connector 

and “G42-19” wire terminal at keyless start control 
module connector

• Between “E03-6” wire terminal at ABS connector and 

“G42-18” wire terminal at keyless start control module 
connector

Is each resistance 1 

Ω

 or less?

Go to Step 5.

Repair open or high 
resistance in 
malfunctional wire 
circuit.

5

Check for short between CAN communication wire 
circuits between ABS and keyless start control module
1) Disconnect connector “G31” from BCM connector 

referring to “BCM Removal and Installation in Section 
10B”.

2) Disconnect connector “G28” from combination meter 

referring to “Combination Meter Removal and Installation 
in Section 9C”.

3) Measure resistance between “E03-12” wire terminal at 

ABS connector and “G42-18” wire terminal at keyless 
start control module connector.

Is resistance infinite?

Go to Step 6.

Repair short between 
CAN communication 
wire circuits.

Immobilizer Control System:  10C-15

DTC P1621: Immobilizer Communication Line Error

S5JB0AA304007

Detecting Condition and Trouble Area

6

Check for short to ground wire circuit in CAN 
communication wire circuits
1) Measure resistance at the following wire terminals.

• Between “E03-6” wire terminal at ABS connector and 

body ground

• Between “E03-12” wire terminal at ABS connector 

and body ground

Is resistance infinite?

Go to Step 7.

Repair short to ground 
wire circuit in CAN 
communication wire 
circuits.

7

Check for short to power supply wire circuit in CAN 
communication wire circuits
1) Measure resistance at the following wire terminals with 

the ignition switch at ON position.
• Between “E03-6” wire terminal at ABS connector and 

body ground

• Between “E03-12” wire terminal at ABS connector 

and body ground

Is voltage 0 V?

Go to Step 8.

Repair short to power 
supply wire circuit in 
CAN communication 
wire circuits.

8

Check of keyless start control module power and 
ground wire circuits
1) Check keyless start control module power and ground 

wire circuits referring to “Keyless Start Control Module 
Power and Ground Circuit Check in Section 10E”.

Are they in normal?

Replace keyless start 
control module with a 
known-good one and 
recheck.

Repair malfunctional 
wire circuit.

Step

Action

Yes

No

Detecting Condition

Trouble Area

Communication error between immobilizer control module 
(ICM) and ECM is detected by ECM.

• Related fuse(s) blown
• Poor connection at immobilizer control module (ICM) 

connector

• Poor connection at ECM connector
• Open in power supply wire circuit
• Open in ground wire circuit
• Open in communication wire circuits
• Short to ground wire circuit in communication wire 

circuits

• Short to power supply wire circuit in communication 

wire circuits

• Short of communication wire circuits
• Immobilizer control module (ICM) faulty
• ECM faulty

10C-16 Immobilizer Control System: 

Troubleshooting

Step

Action

Yes

No

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?

Go to Step 2.

The troubleshooting is 
completed.

2

Fuse check
1) Check if any related fuse is blown.

Is any fuse blown?

Replace blown fuse(s) 
with new one(s).

Go to Step 3.

3

Immobilizer control module (ICM) poor connection 
check
1) Disconnect immobilizer control module (ICM) connector 

“G24” referring to “Immobilizer Control Module (ICM) 
Removal and Installation”.

2) Check if wire connections are normal at immobilizer 

control module (ICM) connector “G24”.

Is each wire connection normal?

Go to Step 4.

Repair poor 
connection(s).

4

ECM poor connection check
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?

Go to Step 5.

Repair poor 
connection(s).

5

Check for open in power supply wire circuit
1) Connect immobilizer control module (ICM) connector 

“G24” referring to “Immobilizer Control Module (ICM) 
Removal and Installation”.

2) With the ignition switch at ON position, check voltage 

between “G24-1” wire terminal at immobilizer control 
module (ICM) and body ground.

Is voltage about 12 V?

Go to Step 6.

Repair open in power 
supply wire circuit.

6

Check for open in ground wire circuit
1) With the ignition switch at ON position, check voltage 

between “G24-2” wire terminal at immobilizer control 
module (ICM) and body ground.

Is voltage 0?

Go to Step 7.

Repair open in ground 
wire circuit.

7

Check for open in communication wire circuit
1) Disconnect immobilizer control module (ICM) connector 

“G24” referring to “Immobilizer Control Module (ICM) 
Removal and Installation”.

2) Disconnect ECM connector “E23” referring to “Engine 

Control Module (ECM) Removal and Installation in 
Section 1C”.

3) Check resistance between “G24-3” wire terminal at 

immobilizer control module (ICM) connector and “E23-
28” wire terminal at ECM connector.

Is resistance infinite?

Repair open in 
communication wire 
circuit.

Go to Step 8.

Immobilizer Control System:  10C-17

8

Check for short to ground circuit in communication wire 
circuit
1) With immobilizer control module (ICM) connector “G24” 

and ECM connector “E23” disconnected, check 
resistance between “G24-3” wire terminal at immobilizer 
control module (ICM) connector and body ground.

Is resistance infinite?

Go to Step 9.

Repair short to ground 
wire circuit in 
communication wire 
circuit.

9

Check for short to power circuit in communication wire 
circuit
1) With immobilizer control module (ICM) connector “G24” 

and ECM connector “E23” disconnected, turn the ignition 
switch to ON position.

2) Check voltage between “G24-3” wire terminal at 

immobilizer control module (ICM) connector and body 
ground.

Is voltage 0 V?

Go to Step 10.

Repair short to power 
supply wire circuit in 
communication wire 
circuit.

10 Check for open in communication wire circuit

1) With immobilizer control module (ICM) connector “G24” 

and ECM connector “E23” disconnected, check 
resistance between “G24-4” wire terminal at immobilizer 
control module (ICM) connector and “E23-13” wire 
terminal at ECM connector.

Is resistance infinite?

Repair open in 
communication wire 
circuit.

Go to Step 11.

11 Check for short to ground wire circuit in communication 

wire circuit
1) With immobilizer control module (ICM) connector “G24” 

and ECM connector “E23” disconnected, check 
resistance between “G24-4” wire terminal at immobilizer 
control module (ICM) connector and body ground.

Is resistance infinite?

Go to Step 12.

Repair short to ground 
wire circuit in 
communication wire 
circuit.

12 Check for short to power circuit in communication wire 

circuit
1) With immobilizer control module (ICM) connector “G24” 

and ECM connector “E23” disconnected, turn the ignition 
switch to ON position.

2) Check voltage between “G24-4” wire terminal at 

immobilizer control module (ICM) connector and body 
ground.

Is voltage 0 V?

Go to Step 13.

Repair short to power 
supply wire circuit in 
communication wire 
circuit.

13 Check for short of communication wire circuit

1) With immobilizer control module (ICM) connector “G24” 

and ECM connector “E23” disconnected, check 
resistance between “G24-3” wire terminal and “G24-4” 
wire terminal at immobilizer control module (ICM) 
connector.

Is resistance infinite?

Go to Step 14.

Repair short of 
communication wire 
circuits.

Step

Action

Yes

No