Nissan Frontier. Manual — part 365
ENGINE CONTROL SYSTEM
EC-31
< SYSTEM DESCRIPTION >
[QR25DE]
C
D
E
F
G
H
I
J
K
L
M
A
EC
N
P
O
ALBIA0515ZZ
1.
EVAP canister vent control valve
(view with bed removed)
2.
EVAP control system pressure
sensor
3.
Drain filter
4.
EVAP canister
5.
Intake manifold collector
(view with air cleaner case removed)
6.
Power steering pressure sensor
7.
Brake pedal position switch (view
with lower instrument panel LH re-
moved)
8.
Stop lamp switch
9.
Brake pedal
10.
Electric throttle control actuator
(view with intake air duct removed)
11. Throttle valve
12. ASCD steering switch
13. CANCEL switch
14. ON OFF (main) switch
15. SET/COAST switch
16. ACCEL/RES switch
17. Clutch pedal position switch
18. Clutch pedal
Front
EC-32
< SYSTEM DESCRIPTION >
[QR25DE]
ENGINE CONTROL SYSTEM
BBIA0640E
MULTIPORT FUEL INJECTION SYSTEM
EC-33
< SYSTEM DESCRIPTION >
[QR25DE]
C
D
E
F
G
H
I
J
K
L
M
A
EC
N
P
O
MULTIPORT FUEL INJECTION SYSTEM
System Description
INFOID:0000000009480724
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 signal 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.
<Fuel increase>
• During warm-up
• When starting the engine
• During acceleration
• Hot-engine operation
• When selector lever is changed from N to D (A/T models)
• High-load, high-speed operation
<Fuel decrease>
• During deceleration
• During high engine speed operation
Sensor
Input Signal to ECM
ECM function
Actuator
Crankshaft position sensor (POS)
Engine speed*
3
Fuel injection & mixture
ratio control
Fuel injector
Camshaft position sensor (PHASE)
Piston position
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
Park/neutral position (PNP) switch (M/T)
TCM (A/T)
Gear position
Knock sensor
Engine knocking condition
Power steering pressure sensor
Power steering operation
Air fuel ratio (A/F) sensor 1
Density of oxygen in exhaust gas
Heated oxygen sensor 2*
1
Density of oxygen in exhaust gas
Combination meter
Vehicle speed*
2
Air conditioner switch
Air conditioner operation*
2
Battery
Battery voltage*
3
EC-34
< SYSTEM DESCRIPTION >
[QR25DE]
MULTIPORT FUEL INJECTION 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 better reduce CO, HC and NOx emissions. This system uses air fuel
ratio (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 air fuel
ratio (A/F) sensor 1, refer to
EC-197, "Component Description"
. 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 air fuel ratio (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 air fuel ratio (A/F) sensor 1 or its circuit
• Insufficient activation of air fuel ratio (A/F) 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 air fuel ratio (A/F)
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 air fuel ratio (A/F) 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 over time to compensate for continual deviation
of the short-term fuel trim from the central value. Continual deviation will occur due to individual engine differ-
ences, wear over time and changes in the usage environment.
PBIB3020E
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст