Suzuki Grand Vitara JB416 / JB420. Manual - part 53

1A-161 Engine General Information and Diagnosis: 

DTC Troubleshooting

NOTE
Before this trouble shooting is performed, read the precautions for DTC troubleshooting referring to 
“Precautions For DTC Troubleshooting”.

 

Step

Action

Yes

No

1

Was “Engine and Emission Control System Check” 
performed?

Go to Step 2.

Go to “Engine and 
Emission Control 
System Check”.

2

Starter signal check
1) Turn OFF ignition switch.
2) Remove ECM from its bracket with ECM connectors 

connected.

3) Start engine, measure voltage between “C37-22” 

terminal of ECM connector and vehicle body ground.

Is voltage 0 – 1 V?

Intermittent trouble. 
Check for intermittent 
referring to “Intermittent 
and Poor Connection 
Inspection in Section 
00”. If OK, substitute a 
known-good ECM and 
recheck.

Go to Step 3.

3

Wire circuit check
1) Disconnect starting motor control relay in fuse box No.2 

with ignition switch turned OFF.

2) Check for proper connection to starting motor control 

relay at “BLK/YEL”, “BLK/RED” and “BLK” (for M/T 
model) wire terminals.

3) Disconnect connector from starting motor.
4) Measure voltage between “C37-22” terminal of ECM 

connector and vehicle body ground with ignition switch 
turned ON.

Is voltage 0 – 1 V?

Go to Step 4.

“BLK/YEL” wire is 
shorted to power circuit.
If wires are OK, 
substitute a known good 
ECM and recheck.

4

Wire circuit check
1) Measure voltage between “BLK/YEL” wire terminal for 

coil side of starting motor control relay connector coil 
side and vehicle body ground with ignition switch turned 
ON.

Is voltage 0 – 1 V?

Check starting motor 
control relay. If OK, 
substitute a known-
good ECM and recheck.

Check ignition switch 
referring to “Ignition 
Switch Inspection in 
Section 9C”.
If ignition switch is OK, 
check for short circuit 
between ignition switch 
and starting motor 
control relay to power 
circuit.

Engine General Information and Diagnosis:  1A-162

DTC P0620: Generator Control Circuit

S5JB0A1104090

System and Wiring Diagram

Generator Control System Description
Refer to “Generator Control System Description”.

DTC Detecting Condition and Trouble Area

DTC Confirmation Procedure

1) With ignition switch turned OFF, connect scan tool to DLC
2) Turn ON ignition switch and clear DTC.
3) Make sure that all accessory switches are tuned OFF.
4) Start engine and warm it up to normal operating temperature (ECT approx. 90 – 95 

°C, 193 – 203 °F).

5) Turn ON the following accessory switches.

• Head light switch.
• Blower motor switch (max position).
• Rear defogger switch.

6) Increase engine speed to 4000 rpm and keep it for 10 sec or more.
7) Decrease engine speed to idle.
8) Check DTC and pending DTC.

IG

L

C

FR

E

4

2

BRN/BLK

C37-8

BRN/BLK

C37-28

B

E23

C37

3

4

18

19

5

6

7

10

11

17

20

47

46

49

50

51

21

22

52

16

25

9

24

14
29

55

57

54 53

59

60

58

2

26

27

28

15
30

56

48

32

31

34

35

36

37

40

42

39 38

44

45

43

41

33

1

12

13

23

8

3

4

18

19

5

6

7

10

11

17

20

47

46

49

50

51

21

22

52

16

25

9

24

14
29

55

57

54 53

59

60

58

2

26

27

28

15
30

56

48

32

31

34

35

36

37

40

42

39 38

44

45

43

41

33

1

12

13

23

8

1

3

5

I5JB0A110063-01

1. Generator

3. Field coil

5. Ignition switch

2. IC regulator

4. ECM

6. Charge lamp

DTC detecting condition

Trouble area

• Battery voltage is higher than specification even through 

generator control is maximum regulation (duty 100%).

• Battery voltage is lower than specification even through 

generator control is minimum regulation (duty 0%) and electric 
load is less than 20 A.

Generator and/or its circuit
Electric load current sensor (for J20 engine)
ECM

1A-163 Engine General Information and Diagnosis: 

DTC Troubleshooting

NOTE
Before this trouble shooting is performed, read the precautions for DTC troubleshooting referring to 
“Precautions For DTC Troubleshooting”.

 

Step

Action

Yes

No

1

Was “Engine and Emission Control System Check” 
performed?

Go to Step 2.

Go to “Engine and 
Emission Control 
System Check”.

2

Generator control circuit check
1) Disconnect connector from generator and ECM with 

ignition switch turned OFF.

2) Check for proper connection of wire terminal to 

generator connector and to ECM connector.

3) If connections are OK, check generator control circuit for 

the following.
• Resistance of generator control circuit wire between 

generator connector and ECM connector is less than 
1 

Ω (continuity check)

• Resistance between generator control circuit wire of 

generator connector and vehicle body ground is 
infinity (ground circuit short check)

• Voltage between generator control circuit wire of 

generator connector and vehicle body ground is 0 V 
with ignition switch tuned ON (power circuit short 
check)

Are they in good condition?

Go to Step 3.

Repair or replace 
defective wire.

3

Generator check
1) Check for generator output referring to “Generator Test 

(Undercharged Battery Check) in Section 1J”.

Is check result satisfactory?

For J20 engine, go to 
Step 4.
For M16 engine, 
Substitute a known 
good ECM and recheck.

Repair or replace 
generator.

4

Electric load current sensor check (for J20 engine)
1) Check for electric load current sensor output referring to 

“Electric Load Current Sensor On-Vehicle Inspection 
(For J20 Engine) in Section 1C”.

Is check result satisfactory?

Substitute a known 
good ECM and recheck.

Replace electric load 
current sensor.

Engine General Information and Diagnosis:  1A-164

DTC P0625 / P0626: Generator Field Terminal Circuit Low / High

S5JB0A1104091

System and Wiring Diagram
Refer to “DTC P0620: Generator Control Circuit”.

Generator Control System Description
Refer to “Generator Control System Description”.

DTC Detecting Condition and Trouble Area

DTC Confirmation Procedure

1) With ignition switch turned OFF, connect scan tool to DLC.
2) Turn ON ignition switch and clear DTC.
3) Make sure that all accessory switch is tuned OFF.
4) Start engine and warm it up to normal operating temperature (ECT approx. 90 – 95 

°C, 193 – 203 °F).

5) Turn ON following accessory switch.

• Head lights switch.
• Blower motor switch (max position).
• Rear defogger switch.

6) Increase engine speed to 4000 rpm and keep it for 10 sec. or more.
7) Decrease engine speed to idle.
8) Check DTC and pending DTC.

DTC detecting condition

Trouble area

P0625:
Generator field coil duty is 100% (low voltage) for more than 
specified time even through generator control is maximum 
regulation (control duty 100%) or Generator field coil duty is 100% 
(low voltage) when engine is starting.
P0626:
Generator field coil duty is 0% (high voltage) for more than 
specified time even through generator control is minimum 
regulation (control duty 0%).

Generator and/or its circuit
ECM