Nissan Altima L32. Manual - part 364

MULTIPORT FUEL INJECTION SYSTEM

EC-577

< FUNCTION DIAGNOSIS >

[QR25DE EXCEPT FOR CALIFORNIA]

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MULTIPORT FUEL INJECTION SYSTEM

System Diagram

INFOID:0000000004349604

System Description

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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.

JMBIA0173GB

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

Intake air temperature sensor

Intake air temperature

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

Battery

Battery voltage*

3

Knock sensor

Engine knocking condition

Power steering pressure sensor

Power steering operation

Heated oxygen sensor 2*

1

Density of oxygen in exhaust gas

ABS actuator and electric unit (control unit)*

2

ABS operation command

BCM

Air conditioner operation*

2

Combination meter

Vehicle speed*

2

EC-578

< FUNCTION DIAGNOSIS >

[QR25DE EXCEPT FOR CALIFORNIA]

MULTIPORT FUEL INJECTION SYSTEM

*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 the crankshaft position sensor (POS), camshaft position

sensor (PHASE) 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>

• During warm-up

• When starting the engine

• During acceleration

• Hot-engine operation

• When selector lever is changed from N to D (CVT models)

• High-load, high-speed operation

<Fuel decrease>

• During deceleration

• During 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 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 A/F sensor 1, refer to

EC-724, "DTC Logic"

. This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mix-

ture).

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 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.

- Deceleration and acceleration

- High-load, high-speed operation

- Malfunction of A/F sensor 1 or its circuit

- Insufficient activation of A/F sensor 1 at low engine coolant temperature

- High engine coolant temperature

- During warm-up

- After shifting from N to D (CVT models)

- When starting the engine

MIXTURE RATIO SELF-LEARNING CONTROL

The mixture ratio feedback control system monitors the mixture ratio signal transmitted from A/F sensor 1.

This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to the theoret-

ical mixture ratio as possible. However, the basic mixture ratio is not necessarily controlled as originally

PBIB2793E

MULTIPORT FUEL INJECTION SYSTEM

EC-579

< FUNCTION DIAGNOSIS >

[QR25DE EXCEPT FOR CALIFORNIA]

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designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic changes dur-

ing 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 A/F sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the the-

oretical 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, operation of the engine at excessively high speeds or oper-

ation of the vehicle at excessively high speeds.

SEF337W

EC-580

< FUNCTION DIAGNOSIS >

[QR25DE EXCEPT FOR CALIFORNIA]

MULTIPORT FUEL INJECTION SYSTEM

Component Parts Location

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1.

Intake valve timing control solenoid 
valve

2.

Ignition coil (with power transistor) 
and spark plug

3.

Knock sensor,
Crankshaft position sensor (POS)

4.

Air fuel ratio (A/F) sensor 1

5.

Camshaft position sensor (PHASE)

6.

Engine coolant temperature sensor

7.

Park/neutral position (PNP) switch

8.

ECM

9.

Refrigerant pressure sensor

10. Battery current sensor

11. IPDM E/R

12. Mass air flow sensor (with intake 

temperature sensor)

13. EVAP service port

14. Electric throttle control actuator

(with built in throttle position sensor 
and throttle control motor)

15. EVAP canister purge volume control 

solenoid valve

16. Fuel injector

17. Power steering pressure sensor

ALBIA0094ZZ