Qashqai J11. Engine control system (K9K) - part 11

U0121 CAN COMMUNICATION

ECK-161

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

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U0121 CAN COMMUNICATION

DTC Logic

INFOID:0000000010434240

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

PERFORM DTC CONFIRMATION PROCEDURE

1.

Turn ignition switch ON and wait at least 3 seconds.

2.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-161, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010434241

1.

CHECK DTC WITH ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT)

Check DTC with ABS actuator and electric unit (control unit). Refer to 

BRC-42, "CONSULT Function"

.

Is DTC detected?

YES

>> Check intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

NO

>> Perform trouble shooting relevant to DTC indicated.

DTC No.

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

U0121

MLTIPLXD TRACTION CNTRL CONN
[Lost communication with anti-lock brake 
system (ABS) control module]
• 1.DEF: INVALID SOURCE COMPUT-

ER MULTIPLEX SIGNALS

• 2.DEF: INVALID SOURCE COMPUT-

ER MULTIPLEX SIGNALS

• 3.DEF: CIRCUIT QUANTITY NOT 

PLAUSIBLE

When ECM is not receiving CAN commu-
nication signal between ABS actuator 
and electric unit (control unit).

ABS actuator and electric unit 
(control unit)

ECK-162

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

U0298 COMMUNICATION WITH DC/DC CONVERTER CONTROL UNIT

U0298 COMMUNICATION WITH DC/DC CONVERTER CONTROL UNIT

DTC Logic

INFOID:0000000010434242

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 

ECK-39, "STOP/START SYSTEM : System Description"

.

CAUTION:

Always drive vehicle at a safe speed.

2.

Restart the engine.

3.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-162, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010434243

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

COMMUNICATION ERROR 
(LOST)
(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

+

–

Condition

Voltage

(Approx.)

DC/DC converter

Connector

Terminal

M22

9

Ground

While cranking with restart

2.0 V or less

Except above

Battery voltage

U0298 COMMUNICATION WITH DC/DC CONVERTER CONTROL UNIT

ECK-163

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

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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 and 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-41, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace DC/DC converter. Refer to 

ECK-402, "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 

ECK-399, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

+

–

Continuity

DC/DC converter

ECM

Connector

Terminal

Connector

Terminal

M22

9

F80

51

Existed

ECK-164

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

DTC Logic

INFOID:0000000010434244

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 

ECK-164, "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 

ECK-164, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010434245

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

COMMUNICATION ERROR (LOST)
(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

F81

141

M22

7

Existed

U0299 LOST COMMUNICATION (DC/DC CONVERTER)

ECK-165

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

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YES

>> Replace DC/DC converter. Refer to 

ECK-402, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

ECK-166

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

U0315 CAN COMMUNICATION [ABS ACTUATOR AND ELECTRIC UNIT (CON-

TROL UNIT)]

U0315 CAN COMMUNICATION [ABS ACTUATOR AND ELECTRIC UNIT
(CONTROL UNIT)]

DTC Logic

INFOID:0000000010434246

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

PERFORM DTC CONFIRMATION PROCEDURE

1.

Turn ignition switch ON and wait at least 3 seconds.

2.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-166, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010434247

1.

CHECK DTC WITH ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT)

Check DTC with ABS actuator and electric unit (control unit). Refer to 

BRC-42, "CONSULT Function"

.

Is DTC detected?

YES

>> Check intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

NO

>> Perform trouble shooting relevant to DTC indicated.

DTC No.

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

U0315

VEHICLE SPEED
(Software incompatibility with anti-lock 
brake system control module)
• 1.DEF: INVALID SERIAL DATA RE-

CEIVED

• 2.DEF: INVALID SOURCE COMPUT-

ER MULTIPLEX SIGNALS

• 3.DEF: CIRCUIT QUANTITY NOT 

PLAUSIBLE

• 4.DEF: INVALID SOURCE COMPUT-

ER MULTIPLEX SIGNALS

ECM receives invalid signal of vehicle 
speed sent from ABS actuator and elec-
tric unit (control unit).

ABS actuator and electric unit 
(control unit)

U0415 CAN COMMUNICATION

ECK-167

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

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U0415 CAN COMMUNICATION

DTC Logic

INFOID:0000000010289717

DTC DETECTION LOGIC

DTC CONFIRMATION PROCEDURE

1.

PERFORM DIAGNOSIS PROCEDURE

NOTE:
DTC U0415 can not duplicate.

>> Proceed to 

ECK-167, "Diagnosis Procedure"

.

Diagnosis Procedure

INFOID:0000000010289718

1.

CHECK DTC WITH ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT)

Check DTC with ABS actuator and electric unit (control unit). Refer to 

BRC-42, "CONSULT Function"

.

Is DTC detected?

YES

>> Check intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

NO

>> Perform trouble shooting relevant to DTC indicated.

DTC No.

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

U0415

MLTIPLXD TRACTION CNTRL CONN
[Invalid data received from anti-lock 
brake system (ABS) control module]
• 1.DEF: IMPLAUSIBLE SIGNAL
• 2.DEF: INVALID SOURCE COMPUT-

ER MULTIPLEX SIGNALS

ECM receives invalid data sent from ABS 
actuator and electric unit (control unit).

ABS actuator and electric unit 
(control unit)

ECK-168

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

B1900 DC/DC CONVERTER

B1900 DC/DC CONVERTER

DTC Logic

INFOID:0000000010289730

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 10 seconds or more to start this procedure.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE-1

1.

Turn ignition switch ON and wait at least 3 seconds.

2.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-168, "Diagnosis Procedure"

.

NO

>> GO TO 3.

3.

PERFORM DTC CONFIRMATION PROCEDURE-2

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.

6.

Check DTC.

Without CONSULT

1.

Activate stop/start system. Refer to 

ECK-39, "STOP/START SYSTEM : System Description"

.

CAUTION:

Always drive vehicle at a safe speed.

2.

Restart the engine.

3.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-168, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010289731

1.

CHECK FUSIBLE LINK

1.

Turn ignition switch OFF.

2.

Check that the following fusible link is not fusing.

Is the fusible link fusing?

YES

>> Replace the fusible link after repairing the applicable circuit.

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

B1900

DC/DC CONVERTER
(DC/DC converter)

DC/DC converter detects power supply 
input 1 is 5.0 V or less and difference 
between power supply input 1 and pow-
er supply input 2 is 4.0 V or more for 3 
seconds.

• Harness and connectors

(DC/DC converter power supply input 1 cir-
cuit is open or shorted.)

• DC/DC converter

Location

Fusible link

Capacity

Fusible link holder

O

30 A

B1900 DC/DC CONVERTER

ECK-169

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

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ECK

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NO

>> GO TO 2.

2.

CHECK DC/DC CONVERTER POWER SUPPLY INPUT 1

1.

Disconnect DC/DC converter harness connector.

2.

Check the voltage between DC/DC converter harness connector and ground.

Is the inspection result normal?

YES

>> GO TO 4.

NO

>> GO TO 3.

3.

CHECK DC/DC CONVERTER POWER SUPPLY INPUT 1 CIRCUIT

1.

Disconnect battery negative terminal.

2.

Check the continuity between DC/DC converter harness connector and fusible link.

Is the inspection result normal?

YES

>> Perform the trouble diagnosis for power supply circuit.

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 DC/DC converter. Refer to 

ECK-402, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

+

−

Voltage

DC/DC converter

Connector

Terminal

M23

1

Ground

Battery voltage

+

−

Continuity

DC/DC converter

Fusible link

Connector

Terminal

M23

1

O

Existed

ECK-170

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

B1901 DC/DC CONVERTER

B1901 DC/DC CONVERTER

DTC Logic

INFOID:0000000010289732

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 10 seconds or more to start this procedure.

>> GO TO 2.

2.

PERFORM DTC CONFIRMATION PROCEDURE-1

1.

Turn ignition switch ON and wait at least 3 seconds.

2.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-170, "Diagnosis Procedure"

.

NO

>> GO TO 3.

3.

PERFORM DTC CONFIRMATION PROCEDURE-2

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.

6.

Check DTC.

Without CONSULT

1.

Activate stop/start system. Refer to 

ECK-39, "STOP/START SYSTEM : System Description"

.

CAUTION:

Always drive vehicle at a safe speed.

2.

Restart the engine.

3.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-170, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010289733

1.

CHECK FUSIBLE LINK

1.

Turn ignition switch OFF.

2.

Check that the following fusible link is not fusing.

Is the fusible link fusing?

YES

>> Replace the fusible link after repairing the applicable circuit.

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

B1901

DC/DC CONVERTER
(DC/DC converter)

DC/DC converter detects power supply 
input 2 is 5.0 V or less and difference 
between power supply input 2 and 
power supply input 1 is 4.0 V or more 
for 3 seconds.

• Harness and connectors

(DC/DC converter power supply input 2 cir-
cuit is open or shorted.)

• DC/DC converter

Location

Fusible link

Capacity

Fusible link holder

N

30 A

B1901 DC/DC CONVERTER

ECK-171

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

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ECK

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NO

>> GO TO 2.

2.

CHECK DC/DC CONVERTER POWER SUPPLY INPUT 2

1.

Disconnect DC/DC converter harness connector.

2.

Check the voltage between DC/DC converter harness connector and ground.

Is the inspection result normal?

YES

>> GO TO 4.

NO

>> GO TO 3.

3.

CHECK DC/DC CONVERTER POWER SUPPLY INPUT 2 CIRCUIT

1.

Disconnect battery negative terminal.

2.

Check the continuity between DC/DC converter harness connector and fusible link.

Is the inspection result normal?

YES

>> Perform the trouble diagnosis for power supply circuit.

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 DC/DC converter. Refer to 

ECK-402, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

+

−

Voltage

DC/DC converter

Connector

Terminal

M23

3

Ground

Battery voltage

+

−

Continuity

DC/DC converter

Fusible link

Connector

Terminal

M23

3

N

Existed

ECK-172

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

B1902 DC/DC CONVERTER

B1902 DC/DC CONVERTER

DTC Logic

INFOID:0000000010289734

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 10 seconds 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 

ECK-39, "STOP/START SYSTEM : System Description"

.

CAUTION:

Always drive vehicle at a safe speed.

2.

Restart the engine.

3.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-172, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010289735

1.

CHECK DC/DC CONVERTER POWER SUPPLY OUTPUT 1

1.

Turn ignition switch ON.

2.

Check the voltage between fuse and ground.

Refer to 

PG-56, "Wiring Diagram - IGNITION POWER SUPPLY -"

.

Is the inspection result normal?

YES

>> GO TO 2.

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

B1902

DC/DC CONVERTER
(DC/DC converter)

DC/DC converter detects power supply 
output 1 is 5.0 V or less when restart 
the engine.

• Harness and connectors

(DC/DC converter power supply output 1 
circuit is open or shorted.)

• DC/DC converter
• Components power-supplied from DC/DC 

output 1

+

–

Voltage

Fuse No.

71

Ground

Battery voltage

72

73

74

B1902 DC/DC CONVERTER

ECK-173

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

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ECK

N

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NO

>> GO TO 3.

2.

CHECK IGNITION POWER SUPPLY CIRCUIT

Check the following units power supply circuit.
• Combination meter
• Steering angle sensor
• Ignition power supply fuse No. 73 circuit
• Ignition power supply fuse No. 74 circuit

Is the inspection result normal?

YES

>> GO TO 4.

NO

>> Repair or replace error-detected parts.

3.

CHECK DC/DC CONVERTER POWER SUPPLY OUTPUT 1 CIRCUIT

1.

Turn ignition switch OFF.

2.

Disconnect battery negative terminal.

3.

Disconnect DC/DC converter harness connector.

4.

Check the continuity between DC/DC converter and Ignition relay.

Refer to 

PG-56, "Wiring Diagram - IGNITION POWER SUPPLY -"

.

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.

4.

CHECK INTERMITTENT INCIDENT

Check intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace DC/DC converter. Refer to 

ECK-402, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

+

–

Continuity

DC/DC converter

Connector

Terminal

M23

4

Ignition relay

Existed

ECK-174

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

B1903 DC/DC CONVERTER

B1903 DC/DC CONVERTER

DTC Logic

INFOID:0000000010289736

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 10 seconds 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 

ECK-39, "STOP/START SYSTEM : System Description"

.

CAUTION:

Always drive vehicle at a safe speed.

2.

Restart the engine.

3.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-174, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010289737

1.

CHECK FUSE-1

Check that the following fuse is not fusing.

Refer to 

PG-11, "Wiring Diagram - BATTERY POWER SUPPLY -"

.

Is the fuse fusing?

YES

>> Replace the fuse after repairing the applicable circuit.

NO

>> GO TO 2.

2.

CHECK DC/DC CONVERTER POWER SUPPLY OUTPUT 2 (BATTERY)

1.

Turn ignition switch OFF.

2.

Check the voltage between fuse and ground.

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

B1903

DC/DC CONVERTER
(DC/DC converter)

DC/DC converter detects power supply 
output 2 is 5.0 V or less when restart 
the engine.

• Harness and connectors

(DC/DC converter power supply output 2 
circuit is open or shorted.)

• DC/DC converter
• Components power-supplied from DC/DC 

output 2

Fuse No.

Capacity

#80

20 A

B1903 DC/DC CONVERTER

ECK-175

< DTC/CIRCUIT DIAGNOSIS >

[K9K]

C

D

E

F

G

H

I

J

K

L

M

A

ECK

N

P

O

Refer to 

PG-11, "Wiring Diagram - BATTERY POWER SUPPLY -"

.

Is the inspection result normal?

YES

>> GO TO 3.

NO

>> Perform trouble diagnosis for battery power supply circuit.

3.

CHECK FUSE-2

Check that the following fuse is not fusing.

Refer to 

PG-11, "Wiring Diagram - BATTERY POWER SUPPLY -"

.

Is the fuse fusing?

YES

>> Replace the fuse after repairing the applicable circuit.

NO

>> GO TO 4.

4.

CHECK DC/DC CONVERTER POWER SUPPLY OUTPUT 2 (ACCESSORY)

1.

Turn ignition switch ON.

2.

Check the voltage between fuse and ground.

Refer to 

PG-49, "Wiring Diagram - ACCESSORY POWER SUPPLY -"

.

Is the inspection result normal?

YES

>> GO TO 5.

NO

>> Perform trouble diagnosis for accessory power supply circuit.

5.

CHECK ACCESSORY RELAY ROUTING CIRCUIT

Check ignition relay routing circuit.
Is the inspection result normal?

YES

>> GO TO 6.

NO

>> Repair or replace error-detected parts.

6.

CHECK INTERMITTENT INCIDENT

Perform intermittent incident. Refer to 

GI-41, "Intermittent Incident"

.

Is the inspection result normal?

YES

>> Replace DC/DC converter. Refer to 

ECH-314, "Removal and Installation"

.

NO

>> Repair or replace error-detected parts.

+

−

Voltage

Fuse No.

#80

Ground

Battery voltage

Fuse No.

Capacity

#76

10 A

#77

10 A

+

–

Voltage

Fuse No.

76

Ground

Battery voltage

77

ECK-176

< DTC/CIRCUIT DIAGNOSIS >

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B1904 DC/DC CONVERTER

B1904 DC/DC CONVERTER

DTC Logic

INFOID:0000000010289738

DTC DETECTION LOGIC

NOTE:
If DTC B1904 is displayed with DTC B1900 or B1901, perform the trouble diagnosis for DTC B1900 or B1901.
Refer to 

ECK-168, "DTC Logic"

 or 

ECK-170, "DTC Logic"

.

1.

PRECONDITIONING

If the other DTC Confirmation Procedure is performed right before this procedure, the ignition switch must be
turned OFF and wait for 10 seconds 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 

ECK-39, "STOP/START SYSTEM : System Description"

.

CAUTION:

Always drive vehicle at a safe speed.

2.

Restart the engine.

3.

Check DTC.

Is DTC detected?

YES

>> Proceed to 

ECK-176, "Diagnosis Procedure"

.

NO

>> INSPECTION END

Diagnosis Procedure

INFOID:0000000010289739

1.

INSPECTION START

1.

Turn ignition switch ON.

2.

Erase DTC.

3.

Perform DTC Confirmation Procedure. Refer to 

ECK-176, "DTC Logic"

.

4.

Check DTC.

Is the DTC B1904 displayed again?

YES

>> Replace DC/DC converter. Refer to 

ECK-402, "Removal and Installation"

.

NO

>> INSPECTION END

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detecting condition

Possible cause

B1904

DC/DC CONVERTER
(DC/DC converter)

DC/DC converter function is malfunc-
tioning.

DC/DC converter