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Infiniti Q45 (FY33). Manual - part 236

SEF623U

SEC056C

SEF877T

SEF625U

DIAGNOSTIC PROCEDURE

INSPECTION START

Go to CHECK POWER SUPPLY

CHECK CIRCUIT.
1. Perform “VC/V BYPASS/V” in “ACTIVE

TEST” mode.

2. Make sure that clicking sound is heard

from the vacuum cut bypass valve.

Go to “CHECK COMPO-
NENT” after procedure

CHECK POWER SUPPLY.
1. Turn ignition switch “OFF”.

2. Disconnect vacuum cut valve bypass

valve harness connector.

3. Turn ignition switch “ON”.
4. Check voltage between terminal

and

ground with CONSULT-II or tester.
Voltage: Battery voltage

Check the following.

Harness connectors

C14

B64

B65

B178

Harness connectors

B102

F64

F63

M49

10A fuse

Harness for open or short
between vacuum cut
valve bypass valve and
fuse

If NG, repair harness or
connectors.

CHECK OUTPUT SIGNAL CIRCUIT.
1. Turn ignition switch “OFF”.

2. Disconnect ECM harness connector.
3. Check harness continuity between ECM

terminal

and terminal

Continuity should exist.
If OK, check harness for short to ground
and short to power.

Check the following.

Harness connectors

F64

B102

B178

B65

Harness or connectors

B64

C14

Harness for open or short
between vacuum cut
valve bypass valve and
ECM

If NG, repair open circuit or
short to ground or short to
power in harness or con-
nectors.

CHECK COMPONENT
(Vacuum cut valve bypass valve).
Refer to “COMPONENT INSPECTION” on
next page.

Replace vacuum cut valve
bypass valve.

Perform “TROUBLE DIAGNOSIS FOR
INTERMITTENT INCIDENT”, EC-117.

INSPECTION END

IDX

TROUBLE DIAGNOSIS FOR DTC P1490

Vacuum Cut Valve Bypass Valve (Circuit)
(Cont’d)

EC-473

SEC057C

SEF351Q

COMPONENT INSPECTION

Vacuum cut valve bypass valve

Check air passage continuity.

Perform “VC/V BYPASS/V” in “ACTIVE TEST” mode.

Condition

VC/V BYPASS/V

Air passage continuity

between

and

Yes

OFF

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ OR ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Condition

Air passage continuity

between

and

12V direct current supply between
terminals

Yes

No supply

If NG or operation takes more than 1 second, replace vacuum cut
valve bypass valve.

TROUBLE DIAGNOSIS FOR DTC P1490

Vacuum Cut Valve Bypass Valve (Circuit)
(Cont’d)

EC-474

SEF623U

Vacuum Cut Valve Bypass Valve

COMPONENT DESCRIPTION

The vacuum cut valve and vacuum cut valve bypass valve are
installed in parallel on the EVAP purge line between the fuel tank
and the EVAP canister.
The vacuum cut valve prevents the intake manifold vacuum from
being applied to the fuel tank.
The vacuum cut valve bypass valve is a solenoid type valve and
generally remains closed. It opens only for on board diagnosis.
The vacuum cut valve bypass valve responds to signals from the
ECM. When the ECM sends an ON (ground) signal, the valve is
opened. The vacuum cut valve is then bypassed to apply intake
manifold vacuum to the fuel tank.

EVAPORATIVE EMISSION SYSTEM DIAGRAM

SEF850U

CONSULT-II REFERENCE VALUE IN DATA MONITOR MODE

Specification data are reference values.

MONITOR ITEM

CONDITION

SPECIFICATION

VC/V BYPASS/V

Ignition switch: ON

OFF

ECM TERMINALS AND REFERENCE VALUE

Specification data are reference values and are measured between each terminal and ground.

CAUTION:

Do not use ECM ground terminals when measuring voltage. Doing so may result in damage to the
ECM’s transistor. Use a ground other than ECM terminals such as the body ground.

TER-

MINAL

NO.

WIRE

COLOR

ITEM

CONDITION

DATA

(DC Voltage)

LG/B

Vacuum cut valve bypass
valve

Ignition switch “ON”

BATTERY VOLTAGE
(11 - 14V)

IDX

TROUBLE DIAGNOSIS FOR DTC P1491

EC-475

ON BOARD DIAGNOSIS LOGIC

Diagnostic Trouble

Code No.

Malfunction is detected when ....

Check Items

(Possible Cause)

P1491
0311

Vacuum cut valve bypass valve does not operate
properly.

Vacuum cut valve bypass valve

Vacuum cut valve

Bypass hoses for clogging

EVAP control system pressure sensor

EVAP canister vent control valve

Hose between fuel tank and vacuum cut valve
clogged

Hose between vacuum cut valve and EVAP canis-
ter clogged

EVAP canister

EVAP purge port of fuel tank for clogging

SEF809X

SEF810X

SEC058C

DIAGNOSTIC TROUBLE CODE CONFIRMATION
PROCEDURE

CAUTION:

Always drive vehicle at a safe speed.
NOTE:
If “DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCE-
DURE” has been previously conducted, always turn ignition
switch “OFF” and wait at least 5 seconds before conducting
the next test.
TESTING CONDITION:

Always perform test at temperature of 0 to 30°C (32 to
86°F).

1) Turn ignition switch “ON”.
2) Start engine and warm it up to normal operating tem-

perature.

3) Turn ignition switch “OFF” and wait at least 5 seconds.
4) Start engine (TCS switch “OFF”) and let it idle for at

least 90 seconds.

5) Select “PURG CN/V & S/V P1493” of “EVAPORATIVE

SYSTEM” in “DTC WORK SUPPORT” mode with CON-
SULT-II.

6) Touch “START”.
7) When the following conditions are met, “TESTING” will

be displayed on the CONSULT-II screen. Maintain the
conditions continuously until “TESTING” changes to
“COMPLETED”. (It will take at least 30 seconds.)
CMPS-RPM (POS): 900 - 6,300 rpm
Vehicle speed: 36 - 120 km/h (22 - 75 MPH)
B/FUEL SCHDL: 2 - 4.8 msec
Selector lever: Suitable position

If “TESTING” is not displayed after 5 minutes, retry
from step 3).
8) Make sure that “OK” is displayed after touching “SELF-

DIAG RESULTS”. If “NG” is displayed, refer to
“TROUBLE DIAGNOSIS FOR DTC P1493”, EC-488.

TROUBLE DIAGNOSIS FOR DTC P1491

Vacuum Cut Valve Bypass Valve (Cont’d)

EC-476

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