2003 NISSAN TEANA Service Manual

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Page 1297 of 3502

NISSAN TEANA 2003 Service Manual PRECAUTIONS
EC-15
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Do not disassemble ECM.
If a battery cable is disconnected, the memory will return to
the ECM value.
The ECM will now start to self-control at its

Page 1298 of 3502

NISSAN TEANA 2003 Service Manual EC-16
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PRECAUTIONS

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 th

Page 1299 of 3502

NISSAN TEANA 2003 Service Manual PRECAUTIONS
EC-17
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Do not depress accelerator pedal when starting.
Immediately after starting, do not rev up engine unneces-
sarily.
Do not rev up engine just prior

Page 1300 of 3502

NISSAN TEANA 2003 Service Manual EC-18
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PREPARATION

PREPARATIONPFP:00002
Special Service ToolsBBS005BC
Tool number
Tool nameDescription
EG17650301
Radiator cap tester
adapterAdapting radiator cap tester to radiator cap and
ra

Page 1301 of 3502

NISSAN TEANA 2003 Service Manual PREPARATION
EC-19
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Commercial Service ToolsBBS005BD
Tool name Description
Quick connector
releaseRemoving fuel tube quick connectors in engine
room
(Available in SEC.

Page 1302 of 3502

NISSAN TEANA 2003 Service Manual EC-20
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ENGINE CONTROL SYSTEM

ENGINE CONTROL SYSTEMPFP:23710
System DiagramBBS005BE
PBIB3287E

Page 1303 of 3502

NISSAN TEANA 2003 Service Manual ENGINE CONTROL SYSTEM
EC-21
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Multiport Fuel Injection (MFI) SystemBBS005BF
INPUT/OUTPUT SIGNAL CHART
*1: This sensor is not used to control the engine system under norm

ENGINE CONTROL SYSTEM
EC-21
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Multiport Fuel Injection (MFI) SystemBBS005BF
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.

During warm-up
When starting the engine
During acceleration
Hot-engine operation
When selector lever is changed from N to D
High-load, high-speed operation

During deceleration
During high engine speed operation
Sensor Input Signal to ECM ECM function Actuator
Crankshaft position sensor (POS)
Camshaft position sensor (PHASE)Engine speed*
3
Piston position
Fuel injection & mixture
ratio controlFuel injector 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
Knock sensor Engine knocking condition
Battery
Battery voltage*
3
Power steering pressure sensor Power steering operation
Heated oxygen sensor 2*
1Density of oxygen in exhaust gas
Wheel sensor
Vehicle speed*
2
Air conditioner switch
Air conditioner operation*2

Page 1304 of 3502

NISSAN TEANA 2003 Service Manual EC-22
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ENGINE CONTROL SYSTEM

MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control

EC-22
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ENGINE CONTROL SYSTEM

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 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
heated oxygen sensor 1, refer to EC-143
. 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.
Deceleration and acceleration
High-load, high-speed operation
Malfunction of heated oxygen sensor 1 or its circuit
Insufficient activation of heated oxygen sensor 1 at low engine coolant temperature
High engine coolant temperature
During warm-up
After shifting from N to D
When starting the engine
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 wire) and characteristic
changes during operation (i.e., fuel 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.
PBIB2953E

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