NISSAN X-TRAIL 2003 Electronic Repair Manual

PRECAUTIONS
EC-17
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lDo not disassemble ECM.
lIf a battery terminal is disconnected, the memory will return
to the ECM value.
The ECM will now start to self-control at its initial value.
Engine operation can vary slightly when the terminal is dis-
connected. However, this is not an indication of a problem.
Do not replace parts because of a slight variation.
lWhen connecting ECM harness connector, fasten it
securely with a lever as far as it will go as shown at right.
lWhen connecting or disconnecting pin connectors into or
from ECM, take care not to damage pin terminals (bend or
break).
Make sure that there are not any bends or breaks on ECM
pin terminal, when connecting pin connectors.
lSecurely connect ECM harness connectors.
A poor connection can cause an extremely high (surge)
voltage to develop in coil and condenser, thus resulting in
damage to ICs.
lKeep engine control system harness at least 10 cm (4 in)
away from adjacent harness, to prevent engine control sys-
tem malfunctions due to receiving external noise, degraded
operation of ICs, etc.
lKeep engine control system parts and harness dry.
lBefore replacing ECM, perform “ECM Terminals and Refer-
ence Value” inspection and make sure ECM functions prop-
erly. Refer toEC-79
.
lHandle mass air flow sensor carefully to avoid damage.
lDo not disassemble mass air flow sensor.
lDo not clean mass air flow sensor with any type of deter-
gent.
lDo not disassemble electric throttle control actuator.
lEven a slight leak in the air intake system can cause seri-
ous problems.
lDo not shock or jar the camshaft position sensor (PHASE),
crankshaft position sensor (POS).
SEF707Y
SEF908W
PBIB0090E
MEF040D

EC-18
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PRECAUTIONS
lAfter 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 Func-
tion Check” should be a good result if the repair is com-
pleted.
lWhen 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.
lDo 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.
lDo not operate fuel pump when there is no fuel in lines.
lTighten fuel hose clamps to the specified torque.
SAT652J
SEF348N
PBIB0513E

PRECAUTIONS
EC-19
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lDo not depress accelerator pedal when starting.
lImmediately after starting, do not rev up engine unneces-
sarily.
lDo not rev up engine just prior to shutdown.
lWhen 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.
–Keep the antenna as far as possible from the electronic
control units.
–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.
–Adjust the antenna and feeder line so that the standing-
wave radio can be kept smaller.
–Be sure to ground the radio to vehicle body.
Wiring Diagrams and Trouble DiagnosisEBS00B0L
When you read Wiring diagrams, refer to the following:
lGI-14, "HowtoReadWiringDiagrams"
lPG-2, "POWER SUPPLY ROUTING"for power distribution circuit
When you perform trouble diagnosis, refer to the following:
lGI-11, "HOW TO FOLLOW TEST GROUPS IN TROUBLE DIAGNOSES"
lGI-24, "How to Perform Efficient Diagnosis for an Electrical Incident"
SEF709Y
SEF708Y

EC-20
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PREPARATION
PREPARATION
PFP:00002
Special Service ToolsEBS00B0M
The actual shapes of Kent-Moore tools may differ from those of special service tools illustrated here.
Commercial Service ToolsEBS00B0N
Tool number
Tool nameDescription
KV10117100
Heated oxygen
sensor wrenchLoosening or tightening heated oxygen sensors
with 22 mm (0.87 in) hexagon nut
KV10114400
Heated oxygen
sensor wrenchLoosening or tightening heated oxygen sensors
a: 22 mm (0.87 in)
S-NT379
S-NT636
Tool name (Kent-
Moore No.)Description
Quick connector
releaseRemoving fuel tube quick connectors in engine
room
(Available in SEC. 164 of PARTS CATALOG:
Part No. 16441 6N210)
Fuel filler cap adapter Checking fuel tank vacuum relief valve opening
pressure
Socket wrench Removing and installing engine coolant
temperature sensor
PBIC0198E
S-NT653
S-NT705

PREPARATION
EC-21
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Oxygen sensor
thread cleanerReconditioning 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
Zirconia Oxygen Sensor
b: 12 mm diameter with pitch 1.25 mm for
Titania Oxygen Sensor
Anti-seize lubricant
(Permatex
TM133AR
or equivalent meeting
MIL specification
MIL-A-907)Lubricating oxygen sensor thread cleaning tool
when reconditioning exhaust system threads. Tool name (Kent-
Moore No.)Description
S-NT778
S-NT779

EC-22
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ENGINE CONTROL SYSTEM
ENGINE CONTROL SYSTEM
PFP:23710
System DiagramEBS00B0O
PBIB0488E

ENGINE CONTROL SYSTEM
EC-23
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Vacuum Hose DrawingEBS00B0P
Refer toEC-22, "System Diagram"for Vacuum Control System.
PBIB0489E

EC-24
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ENGINE CONTROL SYSTEM
System Chart
EBS00B0Q
*1: This sensor is not used to control the engine system under normal conditions.
*2: These signals are sent to the ECM through CAN communication line.
Multiport Fuel Injection (MFI) SystemEBS00B0R
INPUT/OUTPUT SIGNAL CHART
*1: Under normal conditions, this sensor is not for engine control operation.
*2: This signal is sent to the ECM through CAN communication line.Input (Sensor) ECM Function Output (Actuator)
lCamshaft position sensor (PHASE)
lCrankshaft position sensor (POS)
lMass air flow sensor
lEngine coolant temperature sensor
lHeated oxygen sensor 1
lThrottle position sensor
lAccelerator pedal position sensor
lPark/neutral position (PNP) switch
lIntake air temperature sensor
lPower steering pressure sensor
lIgnition switch
lBattery voltage
lKnock sensor
lRefrigerant pressure sensor
lHeated oxygen sensor 2 *1
lTCM (Transmission control module) *2
lESP/TCS/ABS control unit *2
lWheel sensor
lAir conditioner switch
lElectrical loadFuel injection & mixture ratio control Fuel injectors
Electronic ignition system Power transistors
Fuel pump control Fuel pump relay
On board diagnostic system MI (On the instrument panel)
Heated oxygen sensor 1 heater control Heated oxygen sensor 1 heater
Heated oxygen sensor 2 heater control Heated oxygen sensor 2 heater
EVAP canister purge flow controlEVAP canister purge volume control
solenoid valve
Air conditioning cut control Air conditioner relay
Cooling fan control Cooling fan relays
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS)
Engine speed
Piston position
Fuel injec-
tion & mix-
ture ratio
controlFuel injectors Camshaft position sensor (PHASE)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Heated oxygen 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
Ignition switch Start signal
Knock sensor Engine knocking condition
Battery Battery voltage
Power steering pressure sensor Power steering operation
Heated oxygen sensor 2 *1 Density of oxygen in exhaust gas
ESP/TCS/ABS control unit *2 ESP/TCS operation command
Wheel sensor Vehicle speed
Air conditioner switch Air conditioner operation

ENGINE CONTROL SYSTEM
EC-25
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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.

lDuring warm-up
lWhen starting the engine
lDuring acceleration
lHot-engine operation
lWhen selector lever is changed from “N” to “D”
lHigh-load, high-speed operation

lDuring deceleration
lDuring high engine speed operation
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
heated oxygen sensor 1 in the exhaust manifold to monitor if the engine operation is rich or lean. The ECM
adjusts the injection pulse width according to the sensor voltage signal. For more information about heated
oxygen sensor 1, refer toEC-160
. 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 heated oxygen 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.
lDeceleration and acceleration
lHigh-load, high-speed operation
lMalfunction of heated oxygen sensor 1 or its circuit
lInsufficient activation of heated oxygen sensor 1 at low engine coolant temperature
lHigh engine coolant temperature
lDuring warm-up
lAfter shifting from “N” to “D”
lWhen starting the engine
PBIB0121E

EC-26
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ENGINE CONTROL SYSTEM
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from heated oxygen
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 film) 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 heated oxygen sensor 1 indicates whether the mixture ratio is RICH or LEAN compared
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.
FUEL INJECTION TIMING
Two types of systems are used.
Sequential Multiport Fuel Injection System
Fuel is injected into each cylinder during each engine cycle according to the firing order. This system is used
when the engine is running.
Simultaneous Multiport Fuel Injection System
Fuel is injected simultaneously into all four cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The four injectors will then receive the signals two times for each engine cycle.
This system is used when the engine is being started and/or if the fail-safe system (CPU) is operating.
FUEL SHUT-OFF
Fuel to each cylinder is cut off during deceleration or operation of the engine at excessively high speeds.
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