Nissan Frontier D22. Manual — part 232
ENGINE CONTROL SYSTEM
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System Chart
UBS00D0Y
*1: This sensor is not used to control the engine system. They are used only for the on board diagnosis.
*2: This sensor is not used to control the engine system under normal conditions.
*3: This switch will operate in place of the throttle position sensor to control EVAP parts if the sensor malfunctions.
Multiport Fuel Injection (MFI) System
UBS00D0Z
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
by input signals (for engine speed and intake air) from both the camshaft position sensor and the mass air flow
sensor.
Input (Sensor)
ECM Function
Output (Actuator)
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Camshaft position sensor
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Mass air flow sensor
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Engine coolant temperature sensor
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Heated oxygen sensor 1
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Ignition switch
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Throttle position sensor
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Park/neutral position (PNP) switch
●
Air conditioner switch
●
Knock sensor
●
EGR temperature sensor*
1
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Crankshaft position sensor (OBD)
●
EVAP control system pressure sensor*
1
●
Fuel tank temperature sensor
●
Battery voltage
●
Fuel level sensor*
1
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Power steering oil pressure switch
●
Vehicle speed sensor
●
Intake air temperature sensor
●
Heated oxygen sensor 2*
2
●
Closed throttle position switch*
3
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
Heated oxygen sensor 1 monitor & on
board diagnostic system
Malfunction indicator lamp
(On the instrument panel)
EGR control
EGRC-solenoid valve
Heated oxygen sensors 1, 2 heater control
Heated oxygen sensor heater
EVAP canister purge flow control
●
EVAP canister purge volume
control 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 Function
Actuator
Camshaft position sensor
Engine speed and piston position
Fuel injection &
mixture 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
EC-32
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ENGINE CONTROL SYSTEM
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
●
Hot-engine operation
●
When selector lever is changed from N to D
●
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
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
. 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.
●
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
●
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 (A/T models)
●
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 film) and characteristic
changes during operation (i.e., injector clogging) directly affect mixture ratio.
SEF336WB
ENGINE CONTROL SYSTEM
EC-33
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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 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.
Distributor Ignition (DI) System
UBS00D10
INPUT/OUTPUT SIGNAL CHART
SEF337W
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
EC-34
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ENGINE CONTROL SYSTEM
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
above.
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: 1,800 rpm, Tp: 1.50 msec
A
°BTDC
During the following conditions, the ignition timing is revised by the
ECM according to the other data stored in the ECM.
●
At starting
●
During warm-up
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At idle
●
At low battery voltage
●
During 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 Control
UBS00D11
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.
●
When the accelerator pedal is fully depressed.
●
When cranking the engine.
●
When the engine coolant temperature becomes excessively high.
●
When operating power steering and air conditioner during low engine speed or when fully releasing accel-
erator pedal.
●
When engine speed is excessively low.
Fuel Cut Control (at No Load and High Engine Speed)
UBS00D12
INPUT/OUTPUT SIGNAL CHART
SEF742M
Sensor
Input Signal to ECM
ECM Function
Actuator
Air conditioner switch
Air conditioner “ON” signal
Air conditioner
cut control
Air conditioner relay
Throttle position sensor
Throttle valve opening angle
Camshaft position sensor
Engine speed
Engine coolant temperature sensor
Engine coolant temperature
Ignition switch
Start signal
Vehicle speed sensor
Vehicle speed
Power steering oil pressure switch
Power steering operation
Sensor
Input Signal to ECM
ECM Function
Actuator
Vehicle speed sensor
Vehicle speed
Fuel cut control
Fuel injector
Park/neutral position (PNP) switch
Neutral position
Throttle position sensor
Throttle position
Camshaft position sensor
Engine speed
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