Nissan X-Trail 32. Manual - part 960

U0298 DC/DC CONVERTER

EC-969

< DTC/CIRCUIT DIAGNOSIS >

[R9M]

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U0298 DC/DC CONVERTER

DTC Description

INFOID:0000000010935628

DTC DETECTION LOGIC

POSSIBLE CAUSE

• Harness and connectors (Voltage stabilizer signal line is open or circuit shorted.)
• DC/DC converter
 Harness or connectors (CAN communication line is open or shorted.)

FAIL-SAFE

STOP/START SYSTEM

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 

EC-848, "STOP/START SYSTEM : System Description (M/T models)"

(M/T models), 

EC-856, "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 

EC-969, "Diagnosis Procedure"

.

NO-1

>> To check malfunction symptom before repair: Refer to 

GI-44, "Intermittent Incident"

.

NO-2

>> Confirmation after repair: INSPECTION END

Diagnosis Procedure

INFOID:0000000010935629

1.

CHECK VOLTAGE STABILIZER SIGNAL

DTC No.

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

U0298

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

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

Stop/start system operating condition in fail safe mode

Idling or driving the vehicle

Stop/start system operating

Stop

During cranking

(Restart)

—

—

Prohibit the stop/start system operation 
from the next time

EC-970

< DTC/CIRCUIT DIAGNOSIS >

[R9M]

U0298 DC/DC CONVERTER

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.

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.

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-44, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace DC/DC converter. Refer to 

EC-1229, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

4.

CHECK INTERMITTENT INCIDENT

Perform intermittent incident. Refer to 

GI-44, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace ECM. Refer to 

EC-1226, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

+

–

Condition

Voltage

(Approx.)

DC/DC converter

Connector

Terminal

M98

9

Ground

While cranking with restart

2.0 V or less

Except above

Battery voltage

+

–

Continuity

DC/DC converter

ECM

Connector

Terminal

Connector

Terminal

M98

9

F117

37

Existed

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

EC-971

< DTC/CIRCUIT DIAGNOSIS >

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U0299 LOST COMMUNICATION (DC/DC CONVERTER)

DTC Description

INFOID:0000000010935630

DTC DETECTION LOGIC

POSSIBLE CAUSE

• DC/DC converter
• Harness and connectors (LIN communication line)

FAIL-SAFE

Not applicable

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 

EC-971, "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 

EC-971, "Diagnosis Procedure"

.

NO-1

>> To check malfunction symptom before repair: Refer to 

GI-44, "Intermittent Incident"

.

NO-2

>> Confirmation after repair: INSPECTION END

Diagnosis Procedure

INFOID:0000000010935631

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.

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.

DTC No.

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

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 communication signal sent from DC/DC con-

verter.

+

−

Continuity

ECM

DC/DC converter

Connector

Terminal

Connector

Terminal

F117

68

M98

7

Existed

EC-972

< DTC/CIRCUIT DIAGNOSIS >

[R9M]

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

NO

>> Repair or replace error-detected parts.

2.

CHECK INTERMITTENT INCIDENT

Perform intermittent incident. Refer to 

GI-44, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace DC/DC converter. Refer to 

EC-1229, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.