Nissan Pathfinder (2005 year). Instruction — part 146
PRECAUTIONS
EC-19
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2005 Pathfinder
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After performing each TROUBLE DIAGNOSIS, perform DTC
Confirmation Procedure or Overall Function Check.
The DTC should not be displayed in the DTC Confirmation
Procedure if the repair is completed. The Overall Function
Check should be a good result if the repair is completed.
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When measuring ECM signals with a circuit tester, never
allow the two tester probes to contact.
Accidental contact of probes will cause a short circuit and
damage the ECM power transistor.
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Do not use ECM ground terminals when measuring input/
output voltage. Doing so may result in damage to the ECM's
transistor. Use a ground other than ECM terminals, such as
the ground.
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B1 indicates the bank 1, B2 indicates the bank 2 as shown
in the figure.
SEF217U
SEF348N
SEC893C
EC-20
PRECAUTIONS
2005 Pathfinder
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Do not operate fuel pump when there is no fuel in lines.
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Tighten fuel hose clamps to the specified torque.
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Do not depress accelerator pedal when starting.
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Immediately after starting, do not rev up engine unneces-
sarily.
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Do not rev up engine just prior to shutdown.
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When installing C.B. ham radio or a mobile phone, be sure
to observe the following as it may adversely affect elec-
tronic control systems depending on installation location.
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Keep the antenna as far as possible from the electronic
control units.
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Keep the antenna feeder line more than 20 cm (8 in) away
from the harness of electronic controls.
Do not let them run parallel for a long distance.
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Adjust the antenna and feeder line so that the standing-
wave radio can be kept smaller.
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Be sure to ground the radio to vehicle body.
Wiring Diagrams and Trouble Diagnosis
UBS00K34
When you read wiring diagrams, refer to the following:
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GI-15, "How to Read Wiring Diagrams"
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PG-4, "POWER SUPPLY ROUTING CIRCUIT"
for power distribution circuit
When you perform trouble diagnosis, refer to the following:
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GI-11, "HOW TO FOLLOW TEST GROUPS IN TROUBLE DIAGNOSES"
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GI-27, "How to Perform Efficient Diagnosis for an Electrical Incident"
BBIA0529E
SEF709Y
SEF708Y
PREPARATION
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2005 Pathfinder
PREPARATION
PFP:00002
Special Service Tools
UBS00K35
The actual shapes of Kent-Moore tools may differ from those of special service tools illustrated here.
Tool number
(Kent-Moore No.)
Tool name
Description
EG17650301
(J-33984-A)
Radiator cap tester
adapter
Adapting radiator cap tester to radiator cap and ra-
diator filler neck
a: 28 (1.10) dia.
b: 31.4 (1.236) dia.
c: 41.3 (1.626) dia.
Unit: mm (in)
KV10117100
(J-36471-A)
Heated oxygen sensor
wrench
Loosening or tightening heated oxygen sensor
with 22 mm (0.87 in) hexagon nut
KV10114400
(J-38365)
Heated oxygen sensor
wrench
Loosening or tightening air fuel ratio (A/F) sensor
a: 22 mm (0.87 in)
(J-44626)
Air fuel ratio (A/F) sen-
sor wrench
Loosening or tightening air fuel ratio (A/F) sensor 1
(J-44321)
Fuel pressure gauge
kit
Checking fuel pressure
(J-44321-6)
Fuel pressure adapter
Connecting fuel pressure gauge to quick connec-
tor type fuel lines.
(J-45488)
Quick connector re-
lease
Remove fuel tube quick connectors in engine
room
S-NT564
S-NT379
S-NT636
LEM054
LEC642
LBIA0376E
PBIC0198E
EC-22
PREPARATION
2005 Pathfinder
KV109E0010
(J-46209)
Break-out box
Measuring the ECM signals with a circuit tester
KV109E0080
(J-45819)
Y-cable adapter
Measuring the ECM signals with a circuit tester
Tool number
(Kent-Moore No.)
Tool name
Description
S-NT825
S-NT826
PREPARATION
EC-23
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2005 Pathfinder
Commercial Service Tools
UBS00K36
Tool name
(Kent-Moore No.)
Description
Leak detector
i.e.: (J-41416)
Locating the EVAP leak
EVAP service port
adapter
i.e.: (J-41413-OBD)
Applying positive pressure through EVAP service
port
Fuel filler cap adapter
i.e.: (MLR-8382)
Checking fuel tank vacuum relief valve opening
pressure
Socket wrench
Removing and installing engine coolant tempera-
ture sensor
Oxygen sensor thread
cleaner
i.e.: (J-43897-18)
(J-43897-12)
Reconditioning the exhaust system threads before
installing a new oxygen sensor. Use with anti-
seize lubricant shown below.
a: 18 mm diameter with pitch 1.5 mm for Zirco-
nia Oxygen Sensor
b: 12 mm diameter with pitch 1.25 mm for Tita-
nia Oxygen Sensor
Anti-seize lubricant
i.e.: (Permatex
TM
133AR or equivalent
meeting MIL specifica-
tion MIL-A-907)
Lubricating oxygen sensor thread cleaning tool
when reconditioning exhaust system threads.
S-NT703
S-NT704
S-NT815
S-NT705
AEM488
S-NT779
EC-24
ENGINE CONTROL SYSTEM
2005 Pathfinder
ENGINE CONTROL SYSTEM
PFP:23710
System Diagram
UBS00K37
PBIB2527E
ENGINE CONTROL SYSTEM
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2005 Pathfinder
Multiport Fuel Injection (MFI) System
UBS00K38
INPUT/OUTPUT SIGNAL CHART
*1: This sensor is not used to control the engine system under normal conditions.
*2: This signal is sent to the ECM through CAN communication line.
*3: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION
The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of
time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the
ECM memory. The program value is preset by engine operating conditions. These conditions are determined
by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air
flow sensor.
VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION
In addition, the amount of fuel injected is compensated to improve engine performance under various operat-
ing conditions as listed below.
<Fuel increase>
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During warm-up
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When starting the engine
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During acceleration
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Hot-engine operation
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When selector lever is changed from N to D
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High-load, high-speed operation
<Fuel decrease>
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During deceleration
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During high engine speed operation
Sensor
Input Signal to ECM
ECM function
Actuator
Crankshaft position sensor (POS)
Engine speed*
3
Piston position
Fuel injection
& mixture ratio
control
Fuel injector
Camshaft position sensor (PHASE)
Mass air flow sensor
Amount of intake air
Engine coolant temperature sensor
Engine coolant temperature
Air fuel ratio (A/F) sensor 1
Density of oxygen in exhaust gas
Throttle position sensor
Throttle position
Accelerator pedal position sensor
Accelerator pedal position
Park/neutral position (PNP) switch
Gear position
Knock sensor
Engine knocking condition
Battery
Battery voltage*
3
Power steering pressure sensor
Power steering operation
Heated oxygen sensor 2*
1
Density of oxygen in exhaust gas
Air conditioner switch*
2
Air conditioner operation
Wheel sensor*
2
Vehicle speed
EC-26
ENGINE CONTROL SYSTEM
2005 Pathfinder
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst (manifold) can then better reduce CO, HC and NOx emissions. This system uses air
fuel ratio (A/F) sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The
ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about air
fuel ratio (A/F) sensor 1, refer to
. This maintains the mixture ratio within the range of stoichiometric
(ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the three way catalyst (manifold). Even if the switching
characteristics of air fuel ratio (A/F) sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal
from heated oxygen sensor 2.
Open Loop Control
The open loop system condition refers to when the ECM detects any of the following conditions. Feedback
control stops in order to maintain stabilized fuel combustion.
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Deceleration and acceleration
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High-load, high-speed operation
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Malfunction of air fuel ratio (A/F) sensor 1 or its circuit
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Insufficient activation of air fuel ratio (A/F) sensor 1 at low engine coolant temperature
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High engine coolant temperature
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During warm-up
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After shifting from N to D
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When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from air fuel ratio (A/F)
sensor 1. This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to
the theoretical mixture ratio as possible. However, the basic mixture ratio is not necessarily controlled as orig-
inally designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic
changes during operation (i.e., injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This is
then computed in terms of “injection pulse duration” to automatically compensate for the difference between
the two ratios.
“Fuel trim” refers to the feedback compensation value compared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical
value. The signal from air fuel ratio (A/F) sensor 1 indicates whether the mixture ratio is RICH or LEAN com-
pared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and
an increase in fuel volume if it is lean.
“Long term fuel trim” is overall fuel compensation carried out long-term to compensate for continual deviation
of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences,
wear over time and changes in the usage environment.
SEF503YB
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