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YEC129A
ENGINE AND EMISSION CONTROL OVERALL SYSTEMQG16I18DE
Engine Control Component Parts Location (Cont'd)
EC-15
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SEF911W
ENGINE AND EMISSION CONTROL OVERALL SYSTEMQG16I18DE
Engine Control Component Parts Location (Cont'd)
EC-16
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Circuit DiagramNCEC0010
YEC062A
ENGINE AND EMISSION CONTROL OVERALL SYSTEMQG16I18DE
Circuit Diagram
EC-17
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System DiagramNCEC0011
YEC116A
ENGINE AND EMISSION CONTROL OVERALL SYSTEMQG16I18DE
System Diagram
EC-18
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Vacuum Hose DrawingNCEC0012Refer to ªSystem Diagramº on EC-QG-18 for vacuum control system.
NEF231A Fuel pressure
regulator
EVAP canister purge
pipe (to EVAP
canister)
To air duct To air control valve
(Power steering)
EVAP canister purge volume
control solenoid valve
EVAP canister
Air
Fuel tank
ENGINE AND EMISSION CONTROL OVERALL SYSTEMQG16I18DE
Vacuum Hose Drawing
EC-19
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System ChartNCEC0013
Input (Sensor) ECM Function Output (Actuator)
ICamshaft position sensor (PHASE)
IMass air flow sensor
IEngine coolant temperature sensor
IHeated oxygen sensor 1 (front)
IIgnition switch
IThrottle position sensor
IPNP switch
IAir conditioner switch
IKnock sensor
IEGR temperature sensor*1*3
ICrankshaft position sensor (POS)
IBattery voltage
IPower steering oil pressure switch
IVehicle speed sensor or ABS actuator and
electric unit (control unit)
IIntake air temperature sensor
IHeated oxygen sensor 2 (rear)*2
IElectrical load
IRefrigerant pressure sensorFuel injection & mixture ratio control Injectors
Electronic ignition system Power transistor
Idle air control system IACV-AAC valve
Valve timing controlIntake valve timing control sole-
noid valve
Fuel pump control Fuel pump relay
Heated oxygen sensor 1 monitor & on
board diagnostic systemMalfunction indicator
(On the instrument panel)
EGR control*3 EGR volume control valve*3
Heated oxygen sensor 1, 2 heater control Heated oxygen sensor heater
EVAP canister purge flow controlEVAP canister purge volume con-
trol solenoid valve
Cooling fan control Cooling fan relay
Air conditioning cut control Air conditioner relay
*1: This sensor is not used to control the engine system. They are used only for the on board diagnosis.
*2: Under normal conditions, this sensor is not for engine control operation.
*3: If so equipped
ENGINE AND EMISSION CONTROL OVERALL SYSTEMQG16I18DE
System Chart
EC-20
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Multiport Fuel Injection (MFI) System
DESCRIPTIONNCEC0014Input/Output Signal ChartNCEC0014S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed and piston position
Fuel injec-
tion & mix-
ture ratio
controlInjector Camshaft position sensor (PHASE) Cylinder number
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Heated oxygen sensor 1 (front) Density of oxygen in exhaust gas
Throttle position sensorThrottle position
Throttle valve idle position
PNP switch Gear position
Vehicle speed sensor or ABS actuator and
electric unit (control unit)Vehicle speed
Ignition switch Start signal
Air conditioner switch Air conditioner operation
Knock sensor Engine knocking condition
Electrical load Electrical load signal
Battery Battery voltage
Power steering oil pressure switch Power steering operation
Heated oxygen sensor 2 (rear)* Density of oxygen in exhaust gas
* Under normal conditions, this sensor is not for engine control operation.
Basic Multiport Fuel Injection SystemNCEC0014S02The 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.
Various Fuel Injection Increase/Decrease CompensationNCEC0014S03In addition, the amount of fuel injected is compensated to improve engine performance under various oper-
ating conditions as listed below.
IDuring warm-up
IWhen starting the engine
IDuring acceleration
IHot-engine operation
IHigh-load, high-speed operation
IDuring deceleration
IDuring high engine speed operation
IDuring high vehicle speed operation (M/T models)
IExtremely high engine coolant temperature
ENGINE AND EMISSION BASIC CONTROL
SYSTEM DESCRIPTIONQG16I18DE
Multiport Fuel Injection (MFI) System
EC-21
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Mixture Ratio Feedback Control (Closed loop control)NCEC0014S04
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission con-
trol. The three way catalyst can then better reduce CO, HC and NOx emissions. This system uses a heated
oxygen sensor 1 (front) in the exhaust manifold to monitor if 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 (front), refer to EC-QG-132. This maintains the mixture ratio within the range of stoichiomet-
ric (ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 (rear) is located downstream of the three way catalyst. Even if the switching char-
acteristics of the heated oxygen sensor 1 (front) shift, the air-fuel ratio is controlled to stoichiometric by the
signal from the heated oxygen sensor 2 (rear).
Open Loop ControlNCEC0014S05The 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.
IDeceleration and acceleration
IHigh-load, high-speed operation
IMalfunction of heated oxygen sensor 1 (front) or its circuit
IInsufficient activation of heated oxygen sensor 1 (front) at low engine coolant temperature
IHigh engine coolant temperature
IDuring warm-up
IWhen starting the engine
Mixture Ratio Self-learning ControlNCEC0014S06The mixture ratio feedback control system monitors the mixture ratio signal transmitted from the heated oxy-
gen sensor 1 (front). 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 con-
trolled as originally designed. Both manufacturing differences (i.e., mass air flow sensor hot film) and charac-
teristic changes during operation (i.e., 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 ªinjection pulse durationº to automatically compensate for the difference between
the two ratios.
ªFuel trimº refers to the feedback compensation value compared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
ªShort term fuel trimº is the short-term fuel compensation used to maintain the mixture ratio at its theoretical
value. The signal from the heated oxygen sensor 1 (front) 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.
ªLong term fuel trimº 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.
SEF336WA
ENGINE AND EMISSION BASIC CONTROL
SYSTEM DESCRIPTIONQG16I18DE
Multiport Fuel Injection (MFI) System (Cont'd)
EC-22