Nissan Qashqai J11. Manual - part 503

EC9-168

< DTC/CIRCUIT DIAGNOSIS >

[R9M]

U0298 DC/DC CONVERTER

U0298 DC/DC CONVERTER

DTC Logic

INFOID:0000000010309056

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

If the other DTC Confirmation Procedure is performed right before this procedure, the ignition switch must be
turned OFF and wait for 1 minute or more to start this procedure.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE

With CONSULT

1.

Start the engine and warm it up to normal operating temperature.

2.

Press start/stop OFF switch and check that the switch indicator is ON.

3.

Select “AUTO STOP START” in “ACTIVE TEST” mode of “ENGINE” using CONSULT.

4.

Touch “START” and operate stop/start system. (Stop the engine.)

5.

Touch “CANCEL” and restart the engine.

6.

Check DTC.

Without CONSULT

1.

Activate stop/start system. Refer to 

EC9-39, "STOP/START SYSTEM : System Description (M/T models)"

(M/T models), 

EC9-47, "STOP/START SYSTEM : System Description (CVT models)"

 (CVT models).

CAUTION:

Always drive vehicle at a safe speed.

2.

Restart the engine.

3.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

EC9-168, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010309057

1.

CHECK VOLTAGE STABILIZER SIGNAL

With CONSULT

1.

Start the engine and warm it up to normal operating temperature.

2.

Press start/stop OFF switch and check that the switch indicator is ON.

3.

Select “AUTO STOP START” in “ACTIVE TEST” mode of “ENGINE” using CONSULT.

4.

Touch “START” and operate stop/start system. (engine stop.)

5.

Touch “CANCEL” and restart the engine, and then check the voltage between DC/DC converter harness
connector and ground as per the following conditions.

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

U0298

—
(Lost communication with DC 
to DC converter control module 
“A”)

During the restart, the DC/DC converter 
status of the engine communication line 
does not show an decrease in voltage 
after an ECM transmitted voltage stabi-
lizer signal is changed from battery volt-
age to 2.0 V or less.

• Harness and connectors

(Voltage stabilizer signal line is open or cir-
cuit shorted.)

• DC/DC converter

U0298 DC/DC CONVERTER

EC9-169

< DTC/CIRCUIT DIAGNOSIS >

[R9M]

C

D

E

F

G

H

I

J

K

L

M

A

EC9

N

P

O

Is the inspection result normal?

YES

>> GO TO 3.

NO

>> GO TO 2.

2.

CHECK VOLTAGE STABILIZER SIGNAL CIRCUIT

1.

Turn ignition switch OFF.

2.

Disconnect DC/DC converter harness connector, alternator harness connector, and active grille shutter
harness connector.

3.

Disconnect ECM harness connector.

4.

Check the continuity between DC/DC converter harness connector and ECM harness connector.

5.

Also check harness for short to ground and short to power.

Is the inspection result normal?

YES

>> GO TO 4.

NO

>> Repair or replace error-detected parts.

3.

CHECK INTERMITTENT INCIDENT

Perform intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace DC/DC converter. Refer to 

EC9-408, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

4.

CHECK INTERMITTENT INCIDENT

Perform intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace ECM. Refer to 

EC9-405, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

+

–

Condition

Voltage

(Approx.)

DC/DC converter

Connector

Terminal

M22

9

Ground

While cranking with restart

2.0 V or less

Except above

Battery voltage

+

–

Continuity

DC/DC converter

ECM

Connector

Terminal

Connector

Terminal

M22

9

F82

37

Existed

EC9-170

< DTC/CIRCUIT DIAGNOSIS >

[R9M]

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

DTC Logic

INFOID:0000000010499282

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

PRECONDITIONING

If the other DTC Confirmation Procedure is performed right before this procedure, the ignition switch must be
turned OFF and wait for 1 minute or more to start this procedure.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE-1

1.

Turn ignition switch ON and wait at least 10 seconds.

2.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

EC9-170, "Diagnosis Procedure"

.

NO

>> GO TO 3.

3.

PERFORM DTC CONFIRMATION PROCEDURE-2

1.

Start the engine and let it idle for at least 5 minutes.

2.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

EC9-170, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010499283

1.

CHECK ENGINE COMMUNICATION LINE

1.

Turn ignition switch OFF.

2.

Disconnect ECM harness connector.

3.

Disconnect DC/DC converter harness connector, alternator harness connector, and active grille shutter
harness connector.

4.

Check the continuity between ECM harness connector and DC/DC converter harness connector.

5.

Also check harness for short to ground and to power.

Is the inspection result normal?

YES

>> GO TO 2.

NO

>> Repair or replace error-detected parts.

2.

CHECK INTERMITTENT INCIDENT

Perform intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

Is the inspection result normal?

DTC No.

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

U0299

—
(Lost communication with DC to DC con-
verter control module “B”)

• ECM receives an abnormality signal 

sent from DC/DC converter.

• ECM is not receiving LIN communica-

tion signal sent from DC/DC converter.

• DC/DC converter
• Harness and connectors

(LIN communication line)

+

−

Continuity

ECM

DC/DC converter

Connector

Terminal

Connector

Terminal

F82

68

M22

7

Existed

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

EC9-171

< DTC/CIRCUIT DIAGNOSIS >

[R9M]

C

D

E

F

G

H

I

J

K

L

M

A

EC9

N

P

O

YES

>> Replace DC/DC converter. Refer to 

EC9-408, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.