Suzuki Grand Vitara JB416 / JB420. Manual - part 30

1A-69 Engine General Information and Diagnosis: 

8

HO2S heater relay circuit check
1) Measure wire resistance between coil ground terminal of 

relay connector and vehicle body ground.

Is measured resistance lower than 1 

Ω

?

Output wire of relay 
connector is open or 
short to ground.

Repair or replace 
defective circuit.

9

 A/F sensor heater check
1) Check heater resistance of A/F sensor referring to “Air 

Fuel Ratio (A/F) Sensor On-Vehicle Inspection in 
Section 1C”.

Is A/F sensor heater in good condition?

Go to Step 10.

Replace A/F sensor.

10 A/F sensor heater control circuit check

1) Disconnect connector from ECM with ignition switch 

turned OFF.

2) Check for proper connection of A/F sensor heater circuit 

terminal to ECM connector.

3) If connection are OK, measure each wire resistance of 

sensor heater control circuit at ECM connector between 
ECM to A/F sensor and ECM to vehicle body ground.

Is each measured wire resistance lower than 1 

Ω

?

Go to Step 11.

Repair or replace 
defective wire circuit.

11 A/F sensor heater circuit check

1) Measure insulation resistance between control terminal 

of A/F sensor heater and ground terminal of A/F sensor 
heater at ECM connector.

Is measured resistance infinity?

Substitute a known 
good ECM and recheck.

Repair or replace short 
wire.

Step

Action

Yes

No

Engine General Information and Diagnosis:  1A-70

DTC P0037 / P0038: HO2S Heater Control Circuit Low / High (Sensor-2)

S5JB0A1104016

Wiring Diagram

DTC Detecting Condition and Trouble Area

DTC Confirmation Procedure

1) With ignition switch turned OFF, connect scan tool.
2) Turn ON ignition switch and clear DTC using scan tool.
3) Start engine and warm up to normal operating temperature.
4) Run engine at idle speed for 1 min.
5) Check DTC and pending DTC.

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

4

3

9

RED

GRN

PNK

BLK

C37-47  

C37-11  

C37-57  

6

2

7

10

BLK

BLU

WHT

BLK/RED

GRY/GRN

1

8

5

5V  

BLK/WHT

BLK

PNK

*GRN

I5JB0A110032-01

1. HO2S heater relay

4. “O2 HTR” fuse

7. Heater

10. To other sensors

2. Shield wire

5. “IG COIL” fuse

8. To A/F sensor heater

*: For M16 engine

3. Ignition switch

6. HO2S-2

9. ECM

DTC detecting condition

Trouble area

P0037:
HO2S-2 circuit voltage is lower than specification for more than 
specified time continuously even though control duty ratio of HO2S-2 
heater is less than 75% with engine running. (Heater control duty 
pulse is not detected in its monitor signal)
(2 driving cycle detection logic)
P0038:
HO2S-2 circuit voltage is higher than specification for more than 
specified time continuously even though control duty ratio of HO2S-2 
heater is more than 25% with engine running. (Heater control duty 
pulse is not detected in its monitor signal)
(2 driving cycle detection logic)

• HO2S-2 heater
• HO2S-2 heater circuit
• ECM

1A-71 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

HO2S-2 heater circuit check
1) Disconnect connector from HO2S-2 with ignition switch 

turned OFF.

2) Check for proper connection to HO2S-2 connector.
3) If connection are OK, measure voltage between heater 

power terminal of HO2S-2 connector and vehicle body 
ground with ignition switch turned ON.

Is measured voltage 10 – 14 V?

Go to Step 9.

Go to Step 3.

3

HO2S heater fuse check
1) Check for “O2 HTR” fuse (1) blown.

For J20 engine

For M16 engine

Is “O2 HTR” fuse in good condition?

Go to Step 5.

Go to Step 4.

4

A/F sensor and HO2S heater resistance check
1) Disconnect connector from A/F sensor with ignition 

switch turned OFF.

2) Check heater resistance of A/F sensor and HO2S 

referring to “Air Fuel Ratio (A/F) Sensor On-Vehicle 
Inspection in Section 1C” and “Heated Oxygen Sensor 
(HO2S-2) Heater On-Vehicle Inspection in Section 1C”.

Are A/F sensor heater and HO2S heater in good condition?

Go to Step 6.

Replace defective 
sensor.

1

I5JB0A110028-02

1

I5JB0A110029-02

Engine General Information and Diagnosis:  1A-72

5

HO2S heater relay power circuit check
1) Remove integration relay No.2 (for J20 engine) (1) or 

HO2S heater relay (for M16 engine) (2) with ignition 
switch turned OFF.

2) Check for proper connection to relay connector.
3) If connection are OK, measure voltage between each 

relay power terminal of relay connector and vehicle body 
ground with ignition switch tuned ON.

For J20 engine

For M16 engine

Is each measured voltage 10 – 14 V?

Go to Step 6.

Power circuit is open.

6

Check HO2S heater relay
1) Check integration relay No.2 (for J20 engine) or HO2S 

heater relay (for M16 engine) referring to “Control Relay 
Inspection in Section 1C”.

Is it in good condition?

Go to Step 7.

Replace relay.

7

HO2S-2 heater circuit check
1) Measure insulation resistance between heater terminals 

of HO2S-2 connector.

Is measured resistance infinity?

Go to Step 8.

Repair or replace short 
wire.

8

HO2S heater relay circuit check
1) Measure wire resistance between coil ground terminal of 

relay connector and vehicle body ground.

Is measured resistance lower than 1 

Ω

?

Output wire of relay 
connector is open or 
short to ground.

Repair or replace 
defective circuit.

9

HO2S-2 heater check
1) Check heater resistance of HO2S-2 referring to “Heated 

Oxygen Sensor (HO2S-2) Heater On-Vehicle Inspection 
in Section 1C”.

Is HO2S-2 heater in good condition?

Go to Step 10.

Replace HO2S-2.

Step

Action

Yes

No

1

I5JB0A110030-02

2

I5JB0A110031-03