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Nissan Pathfinder (2008 year). Manual - part 246

TROUBLE DIAGNOSIS - SPECIFICATION VALUE

EC-85

< COMPONENT DIAGNOSIS >

[VQ40DE]

COMPONENT DIAGNOSIS

TROUBLE DIAGNOSIS - SPECIFICATION VALUE

Description

INFOID:0000000001370573

The specification (SP) value indicates the tolerance of the value that is displayed in “SPEC” of “DATA MONI-
TOR” mode of CONSULT-III during normal operation of the Engine Control System. When the value in “SPEC”
of “DATA MONITOR” mode is within the SP value, the Engine Control System is confirmed OK. When the
value “SPEC” of “DATA MONITOR” mode is NOT within the SP value, the Engine Control System may have
one or more malfunctions.
The SP value is used to detect malfunctions that may affect the Engine Control System, but will not light the
MIL.
The SP value will be displayed for the following three items:
• B/FUEL SCHDL (The fuel injection pulse width programmed into ECM prior to any learned on board correc-

tion)

• A/F ALPHA-B1/B2 (The mean value of air-fuel ratio feedback correction factor per cycle)
• MAS A/F SE-B1 (The signal voltage of the mass air flow sensor)

Testing Condition

INFOID:0000000001370574

• Vehicle driven distance: More than 5,000 km (3,107 miles)
• Barometric pressure: 98.3 - 104.3 kPa (1.003 - 1.064 kg/cm

, 14.25 - 15.12 psi)

• Atmospheric temperature: 20 - 30

C (68 - 86

• Engine coolant temperature: 75 - 95

C (167 - 203

• Transmission: Warmed-up*

• Electrical load: Not applied*

• Engine speed: Idle
*1: After the engine is warmed up to normal operating temperature, drive vehicle until “FLUID TEMP SE” (A/T
fluid temperature sensor signal) indicates more than 60

C (140

F).

*2: Rear window defogger switch, air conditioner switch, lighting switch are OFF. Steering wheel is straight
ahead.

Inspection Procedure

INFOID:0000000001370575

NOTE:
Perform “SPEC” of “DATA MONITOR” mode in maximum scale display.

Perform

EC-20, "Basic Inspection"

Confirm that the testing conditions indicated above are met.

Select “B/FUEL SCHDL”, “A/F ALPHA-B1”, “A/F ALPHA-B2” and “MAS A/F SE-B1” in “SPEC” of “DATA
MONITOR” mode with CONSULT-III.

Make sure that monitor items are within the SP value.

If NG, go to

EC-85, "Diagnosis Procedure"

Diagnosis Procedure

INFOID:0000000001370576

OVERALL SEQUENCE

EC-86

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TROUBLE DIAGNOSIS - SPECIFICATION VALUE

PBIB2268E

TROUBLE DIAGNOSIS - SPECIFICATION VALUE

EC-87

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DETAILED PROCEDURE

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”

Start engine.

Confirm that the testing conditions are met. Refer to

EC-85, "Testing Condition"

Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.
NOTE:

PBIB3214E

EC-88

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TROUBLE DIAGNOSIS - SPECIFICATION VALUE

Check “A/F ALPHA-B1”, “A/F ALPHA-B2” for approximately 1 minute because they may fluctuate. It is NG
if the indication is out of the SP value even a little.

OK or NG

>> GO TO 17.

NG (Less than the SP value)>>GO TO 2.
NG (More than the SP value)>>GO TO 3.

CHECK “B/FUEL SCHDL”

Select “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and make sure that the indication is within the
SP value.

OK or NG

>> GO TO 4.

NG (More than the SP value)>>GO TO 19.

CHECK “B/FUEL SCHDL”

Select “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and make sure that the indication is within the
SP value.

OK or NG

>> GO TO 6.

NG (More than the SP value)>>GO TO 6.
NG (Less than the SP value)>>GO TO 25.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”

Stop the engine.

Disconnect PCV hose, and then plug it.

Start engine.

Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.

OK or NG

>> GO TO 5.

>> GO TO 6.

CHANGE ENGINE OIL

Stop the engine.

Change engine oil.
NOTE:
This symptom may occur when a large amount of gasoline is mixed with engine oil because of driving
conditions (such as when engine oil temperature does not rise enough since a journey distance is too
short during winter). The symptom will not be detected after changing engine oil or changing driving con-
dition.

>> INSPECTION END

CHECK FUEL PRESSURE

Check fuel pressure. (Refer to

EC-481, "Fuel Pressure Check"

OK or NG

>> GO TO 9.

NG (Fuel pressure is too high)>>Replace fuel pressure regulator, refer to

EC-481, "Fuel Pressure Check"

GO TO 8.

NG (Fuel pressure is too low)>>GO TO 7.

DETECT MALFUNCTIONING PART

Check the following.

Clogged and bent fuel hose and fuel tube

Clogged fuel filter

Fuel pump and its circuit (Refer to

EC-396, "Description"

If NG, repair or replace the malfunctioning part. (Refer to

EC-85, "Diagnosis Procedure"

If OK, replace fuel pressure regulator.

TROUBLE DIAGNOSIS - SPECIFICATION VALUE

EC-89

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>> GO TO 8.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”

Start engine.

Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.

OK or NG

>> INSPECTION END

>> GO TO 9.

PERFORM POWER BALANCE TEST

Perform “POWER BALANCE” in “ACTIVE TEST” mode.

Make sure that the each cylinder produces a momentary engine speed drop.

OK or NG

>> GO TO 12.

>> GO TO 10.

10.

DETECT MALFUNCTIONING PART

Check the following.

Ignition coil and its circuit (Refer to

EC-400, "Component Description"

Fuel injector and its circuit (Refer to

EC-392, "Component Description"

Intake air leakage

Low compression pressure (Refer to

EM-22, "Compression Pressure"

If NG, repair or replace the malfunctioning part.
If OK, replace fuel injector. (It may be caused by leakage from fuel injector or clogging.)

>> GO TO 11.

11.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”

Start engine.

Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.

OK or NG

>> INSPECTION END

>> GO TO 12.

12.

CHECK A/F SENSOR 1 FUNCTION

Perform all DTC Confirmation Procedure related with A/F sensor 1.
• For DTC P0130, P0150, refer to

EC-142, "DTC Confirmation Procedure"

• For DTC P0131, P0151, refer to

EC-146, "DTC Confirmation Procedure"

• For DTC P0132, P0152, refer to

EC-150, "DTC Confirmation Procedure"

• For DTC P0133, P0153, refer to

EC-154, "DTC Confirmation Procedure"

• For DTC P2A00, P2A03, refer to

EC-378, "DTC Confirmation Procedure"

OK or NG

>> GO TO 15.

>> GO TO 13.

13.

CHECK A/F SENSOR 1 CIRCUIT

Perform Diagnostic Procedure according to corresponding DTC.

>> GO TO 14.

14.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”

Start engine.

Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.

OK or NG

EC-90

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TROUBLE DIAGNOSIS - SPECIFICATION VALUE

>> INSPECTION END

>> GO TO 15.

15.

DISCONNECT AND RECONNECT ECM HARNESS CONNECTOR

Stop the engine.

Disconnect ECM harness connector. Check pin terminal and connector for damage, and then reconnect it.

>> GO TO 16.

16.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”

Start engine.

Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.

OK or NG

>> INSPECTION END

>> Detect malfunctioning part according to

EC-470, "Symptom Matrix Chart"

17.

CHECK “B/FUEL SCHDL”

Select “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and make sure that the indication is within the
SP value.
OK or NG

>> INSPECTION END

NG (More than the SP value)>>GO TO 18.
NG (Less than the SP value)>>GO TO 25.

18.

DETECT MALFUNCTIONING PART

Check for the cause of large engine friction. Refer to the following.

Engine oil level is too high

Engine oil viscosity

Belt tension of power steering, alternator, A/C compressor, etc. is excessive

Noise from engine

Noise from transmission, etc.

Check for the cause of insufficient combustion. Refer to the following.

Valve clearance malfunction

Intake valve timing control function malfunction

Camshaft sprocket installation malfunction, etc.

>> Repair or replace malfunctioning part, and then GO TO 30.

19.

CHECK INTAKE SYSTEM

Check for the cause of uneven air flow through mass air flow sensor. Refer to the following.
• Crushed air ducts
• Malfunctioning seal of air cleaner element
• Uneven dirt of air cleaner element
• Improper specification of intake air system

OK or NG

>> GO TO 21.

>> Repair or replace malfunctioning part, and then GO TO 20.

20.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”, AND “B/FUEL SCHDL”

Select “A/F ALPHA-B1”, “A/F ALPHA-B2”, and “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and
make sure that the each indication is within the SP value.

OK or NG

>> INSPECTION END

NG (“B/FUEL SCHDL” is more, “A/F ALPHA-B1”, “A/F ALPHA-B2” are less than the SP value)>>GO TO 21.

21.

DISCONNECT AND RECONNECT MASS AIR FLOW SENSOR HARNESS CONNECTOR

Stop the engine.

TROUBLE DIAGNOSIS - SPECIFICATION VALUE

EC-91

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Disconnect mass air flow sensor harness connector. Check pin terminal and connector for damage and
then reconnect it again.

>> GO TO 22.

22.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”

Start engine.

Select “A/F ALPHA-B1”, “A/F ALPHA-B2” in “SPEC” of “DATA MONITOR” mode, and make sure that the
each indication is within the SP value.

OK or NG

>> 1.

Detect malfunctioning part of mass air flow sensor circuit and repair it. Refer to

EC-118

GO TO 29.

>> GO TO 23.

23.

CHECK “MAS A/F SE-B1”

Select “MAS A/F SE-B1” in “SPEC” of “DATA MONITOR” mode, and make sure that the indication is within the
SP value.

OK or NG

>> GO TO 24.

NG (More than the SP value)>>Replace mass air flow sensor, and then GO TO 29.

24.

REPLACE ECM

Replace ECM.

Perform initialization of NVIS(NATS) system and registration of all NVIS(NATS) ignition key IDs. Refer to

SEC-8, "ECM RE-COMMUNICATING FUNCTION : Special Repair Requirement"

(with Intelligent Key

system) or

SEC-100, "ECM RE-COMMUNICATING FUNCTION : Special Repair Requirement"

(without

Intelligent Key system).

Perform

EC-25, "VIN Registration"

Perform

EC-26, "Accelerator Pedal Released Position Learning"

Perform

EC-26, "Throttle Valve Closed Position Learning"

Perform

EC-26, "Idle Air Volume Learning"

>> GO TO 29.

25.

CHECK INTAKE SYSTEM

OK or NG

>> GO TO 27.

>> Repair or replace malfunctioning part, and then GO TO 26.

26.

CHECK “B/FUEL SCHDL”

Select “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and make sure that the indication is within the
SP value.

OK or NG

>> INSPECTION END

NG (Less than the SP value)>>GO TO 27.

27.

CHECK “MAS A/F SE-B1”

Select “MAS A/F SE-B1” in “SPEC” of “DATA MONITOR” mode, and make sure that the indication is within the
SP value.

OK or NG

>> GO TO 28.

NG (Less than the SP value)>>Replace mass air flow sensor, and then GO TO 30.

EC-92

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TROUBLE DIAGNOSIS - SPECIFICATION VALUE

28.

CHECK INTAKE SYSTEM

Check for the cause of air leak after the mass air flow sensor. Refer to the following.
• Disconnection, looseness, and cracks in air duct
• Looseness of oil filler cap
• Disconnection of oil level gauge
• Open stuck, breakage, hose disconnection, or cracks of PCV valve
• Disconnection or cracks of EVAP purge hose, open stuck of EVAP canister purge volume control solenoid

valve

• Malfunctioning seal of rocker cover gasket
• Disconnection, looseness, or cracks of hoses, such as vacuum hose, connecting to intake air system parts
• Malfunctioning seal of intake air system, etc.

>> GO TO 30.

29.

CHECK “A/F ALPHA-B1”, “A/F ALPHA-B2”, AND “B/FUEL SCHDL”

Select “A/F ALPHA-B1”, “A/F ALPHA-B2”, and “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and
make sure that the each indication is within the SP value.

OK or NG

>> INSPECTION END

>> Detect malfunctioning part according to

EC-470, "Symptom Matrix Chart"

30.

CHECK “B/FUEL SCHDL”

Select “B/FUEL SCHDL” in “SPEC” of “DATA MONITOR” mode, and then make sure that the indication is
within the SP value.

OK or NG

>> INSPECTION END

>> Detect malfunctioning part according to

EC-470, "Symptom Matrix Chart"

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