Nissan Frontier D22. Manual - part 524

ENGINE CONTROL SYSTEM

EC-1199

[VG33ER]

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Vacuum Hose Drawing

UBS00DRO

Refer to 

EC-1198, "System Diagram"

  for Vacuum Control System.

PBIB1342E

EC-1200

[VG33ER]

ENGINE CONTROL SYSTEM

System Chart

UBS00DRP

*1: This sensor is not used to control the engine system. They are used only for the on board diagnosis.
*2: The DTC related to A/T will be sent to ECM.
*3: This sensor is not used to control the engine system under normal conditions.
*4: This switch will operate in place of the throttle position sensor to control EVAP parts if the sensor malfunctions.

Multiport Fuel Injection (MFI) System

UBS00DRQ

INPUT/OUTPUT SIGNAL CHART

*: This sensor is not used to control the engine system under normal conditions.

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

Input (Sensor)

ECM Function

Output (Actuator)

●

Camshaft position sensor

●

Mass air flow sensor

●

Engine coolant temperature sensor

●

Heated oxygen sensor 1

●

Ignition switch

●

Throttle position sensor

●

Closed throttle position switch *

4

●

Park/neutral position (PNP) switch

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Air conditioner switch

●

Knock sensor

●

Intake air temperature sensor

●

EVAP control system pressure sensor *

1

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Battery voltage

●

Power steering oil pressure switch

●

Vehicle speed sensor

●

Fuel tank temperature sensor *

1

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Crankshaft position sensor (OBD) *

1

●

Heated oxygen sensor 2 *

3

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TCM (Transmission control module) *

2

●

Ambient air temperature switch

Fuel injection & mixture ratio control

Fuel injector

Distributor ignition system

Power transistor

Idle air control system

IACV-AAC valve and IACV-FICD 
solenoid valve

Fuel pump control

Fuel pump relay

On board diagnostic system

MIL (On the instrument panel)

Supercharged air control

SCB valve control solenoid valve

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 control

EVAP canister purge volume con-
trol solenoid valve

Air conditioning cut control

Air conditioner relay

ON BOARD DIAGNOSIS for EVAP system

●

EVAP canister vent control 
valve

●

Vacuum cut valve bypass valve

Sensor

Input Signal to ECM

ECM func-

tion

Actuator

Camshaft position sensor

Engine speed and piston position

Fuel injec-
tion & mix-
ture ratio 
control

Fuel 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
Throttle valve idle position

Park/neutral position (PNP) switch

Gear position

Vehicle speed sensor

Vehicle speed

Ignition switch

Start signal

Air conditioner switch

Air conditioner operation

Knock sensor

Engine knocking condition

Battery

Battery voltage

Power steering oil pressure switch

Power steering operation

Heated oxygen sensor 2*

Density of oxygen in exhaust gas

ENGINE CONTROL SYSTEM

EC-1201

[VG33ER]

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by input signals (for engine speed and intake air) from both the camshaft 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

●

When selector lever is changed from N to D (A/T models) 

●

High-load, high-speed operation

<Fuel decrease>

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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
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 the
heated oxygen sensor 1, refer to 

EC-1375

 . 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 the heated oxygen sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal
from the 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 heated oxygen sensor 1 or its circuit

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Insufficient activation of heated oxygen sensor 1 at low engine coolant temperature

●

High engine coolant temperature

●

During warm-up

●

When starting the engine

MIXTURE RATIO SELF-LEARNING CONTROL

The mixture ratio feedback control system monitors the mixture ratio signal transmitted from the heated oxy-
gen 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
originally 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.

PBIB0121E

EC-1202

[VG33ER]

ENGINE CONTROL SYSTEM

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 the heated oxygen 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.

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 six cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The six 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.

Distributor Ignition (DI) System

UBS00DRR

INPUT/OUTPUT SIGNAL CHART

SEF179U

Sensor

Input Signal to ECM

ECM function

Actuator

Camshaft position sensor

Engine speed and piston position

Ignition timing 
control

Power transistor

Mass air flow sensor

Amount of intake air

Engine coolant temperature sensor

Engine coolant temperature

Throttle position sensor

Throttle position
Throttle valve idle position

Vehicle speed sensor

Vehicle speed

Ignition switch

Start signal

Knock sensor

Engine knocking

Park/neutral position (PNP) switch

Gear position

Battery

Battery voltage