NISSAN X-TRAIL 2003 Electronic Repair Manual

ENGINE CONTROL SYSTEM
EC-387
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ENGINE CONTROL SYSTEMPFP:23710
System DiagramEBS00BER
PBIB0488E

EC-388
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ENGINE CONTROL SYSTEM
Vacuum Hose Drawing
EBS00BES
Refer toEC-387, "System Diagram"for Vacuum Control System.
PBIB0489E

ENGINE CONTROL SYSTEM
EC-389
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System ChartEBS00BET
*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) SystemEBS00BEU
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
functionActuator
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

EC-390
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ENGINE CONTROL SYSTEM
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-490
. 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

ENGINE CONTROL SYSTEM
EC-391
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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.
SEF337W

EC-392
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ENGINE CONTROL SYSTEM
Electronic Ignition (EI) System
EBS00BEV
INPUT/OUTPUT SIGNAL CHART
SYSTEM DESCRIPTION
The ignition timing is controlled by the ECM to maintain the best air-
fuel ratio for every running condition of the engine. The ignition tim-
ing data is stored in the ECM. This data forms the map shown.
The ECM receives information such as the injection pulse width and
camshaft position sensor signal. Computing this information, ignition
signals are transmitted to the power transistor.
e.g.,N:1,800rpm,Tp:1.50msec
A°BTDC
During the following conditions, the ignition timing is revised by the
ECM according to the other data stored in the ECM.
lAt starting
lDuring warm-up
lAt idle
lAt low battery voltage
lDuring acceleration
The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed
within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not
operate under normal driving conditions. If engine knocking occurs, the knock sensor monitors the condition.
The signal is transmitted to the ECM. The ECM retards the ignition timing to eliminate the knocking condition.
Air Conditioning Cut ControlEBS00BEW
INPUT/OUTPUT SIGNAL CHART
SYSTEM DESCRIPTION
This system improves engine operation when the air conditioner is used.
Under the following conditions, the air conditioner is turned off.
Sensor Input Signal to ECMECM
functionActuator
Crankshaft position sensor (POS)
Engine speed
Piston position
Ignition
timing con-
trolPower transistor Camshaft position sensor (PHASE)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Ignition switch Start signal
Knock sensor Engine knocking
Park/neutral position (PNP) switch Gear position
Battery Battery voltage
Wheel sensor Vehicle speed
SEF742M
Sensor Input Signal to ECM ECM function Actuator
Air conditioner switch Air conditioner “ON” signal
Air conditioner
cut controlAir conditioner relay Throttle position sensor Throttle valve opening angle
Crankshaft position sensor (POS) Engine speed
Engine coolant temperature sensor Engine coolant temperature
Ignition switch Start signal
Refrigerant pressure sensor Refrigerant pressure
Power steering pressure sensor Power steering operation
Wheel sensor Vehicle speed

ENGINE CONTROL SYSTEM
EC-393
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EC
lWhen the accelerator pedal is fully depressed.
lWhen cranking the engine.
lAt high engine speeds.
lWhen the engine coolant temperature becomes excessively high.
lWhen operating power steering during low engine speed or low vehicle speed.
lWhen engine speed is excessively low.
lWhen refrigerant pressure is excessively low or high.
Fuel Cut Control (at No Load and High Engine Speed)EBS00BEX
INPUT/OUTPUT SIGNAL CHART
SYSTEM DESCRIPTION
If the engine speed is above 1,800 rpm with no load (for example, in neutral and engine speed over 1,800
rpm) fuel will be cut off after some time. The exact time when the fuel is cut off varies based on engine speed.
Fuel cut will operate until the engine speed reaches 1,500 rpm, then fuel cut is cancelled.
NOTE:
This function is different from deceleration control listed under “Multiport Fuel Injection (MFI) System”,EC-389
.
CAN communicationEBS00BEY
SYSTEM DESCRIPTION
CAN (Controller Area Network) is a serial communication line for real time application. It is an on-vehicle mul-
tiplex communication line with high data communication speed and excellent error detection ability. Many elec-
tronic control units are equipped onto a vehicle, and each control unit shares information and links with other
control units during operation (not independent). In CAN communication, control units are connected with 2
communication lines (CAN H line, CAN L line) allowing a high rate of information transmission with less wiring.
Each control unit transmits/receives data but selectively reads required data only.
FOR A/T MODELS
System Diagram
Input/Output Signal Chart
T: Transmit R: Receive Sensor Input Signal to ECMECM
functionActuator
Park/neutral position (PNP) switch Neutral position
Fuel cut
controlFuel injectors Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Engine coolant temperature sensor Engine coolant temperature
Crankshaft position sensor (POS) Engine speed
Wheel sensor Vehicle speed
SKIA0884E
Signals ECM TCM
Engine speed signal T R
Engine coolant temperature signal T R

EC-394
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ENGINE CONTROL SYSTEM
FOR M/T MODELS
System Diagram
Input/Output Signal Chart
T: Transmit R: Receive Accelerator pedal position signal T R
A/T self-diagnosis signal R TSignals ECM TCM
SKIA0885E
Signals ECMSteering wheel
angle sensor4WD control unitESP/ TCS / ABS
control unit
Engine speed signal T R R
Accelerator pedal position signal T R
ESP operation signal R R T
TCS operation signal R R T
ABS operation signal R R T
Stop lamp switch signalRT
Steering wheel angle sensor signal T R
ESP-OFFSW signalRT
Wheel speed sensor signalRT
4WD Mode signalTR

BASIC SERVICE PROCEDURE
EC-395
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BASIC SERVICE PROCEDUREPFP:00018
Idle Speed and Ignition Timing CheckEBS00BEZ
IDLE SPEED
lUsing CONSULT-II
Check idle speed in “DATA MONITOR” mode with CONSULT-II.
IGNITION TIMING
Any of following two methods may be used.
lMethod A
–Attach timing light to loop wire as shown.
–Check ignition timing.
lMethod B
–Remove No. 1 ignition coil.
–Connect No. 1 ignition coil and No. 1 spark plug with suitable
high-tension wire as shown, and attach timing light clamp to this
wire.
SEF058Y
PBIB0515E
PBIB0509E
PBIB0516E

EC-396
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BASIC SERVICE PROCEDURE
–Check ignition timing.
Throttle Valve Closed Position LearningEBS00BF0
DESCRIPTION
“Throttle Valve Closed Position Learning” is an operation to learn the fully closed position of the throttle valve
by monitoring the throttle position sensor output signal. It must be performed each time harness connector of
electric throttle control actuator or ECM is disconnected.
OPERATION PROCEDURE
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch “ON”.
3. Turn ignition switch “OFF” wait at least 10 seconds.
Make sure that throttle valve moves during above 10 seconds by confirming the operating sound.
Accelerator Pedal Released Position LearningEBS00BLT
DESCRIPTION
“Accelerator Pedal Released Position Learning” is an operation to learn the fully released position of the accel-
erator pedal by monitoring the accelerator pedal position sensor output signal. It must be performed each time
harness connector of accelerator pedal position sensor or ECM is disconnected.
OPERATION PROCEDURE
1. Make sure that accelerator pedal is fully released.
2. Turn ignition switch “ON” and wait at least 2 seconds.
3. Turn ignition switch “OFF” wait at least 10 seconds.
4. Turn ignition switch “ON” and wait at least 2 seconds.
5. Turn ignition switch “OFF” wait at least 10 seconds.
Idle Air Volume LearningEBS00BF1
DESCRIPTION
“Idle Air Volume Learning” is an operation to learn the idle air volume that keeps each engine within the spe-
cific range. It must be performed under any of the following conditions:
lEach time electric throttle control actuator or ECM is replaced.
lIdle speed or ignition timing is out of specification.
SEF166Y
PBIB0514E