Service Manuals, User Guides, Schematic Diagrams or docs for : . Car Manuals Subaru Impreza 2001-2002.2004-2007 Approved Subaru Impreza 2004 WRX STi 08. MECHANISM AND FUNCTION 02. FUEL INJECTION (FUEL SYSTEM) 05. Control System
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W1860BE.book Page 28 Tuesday, January 28, 2003 11:01 PM
CONTROL SYSTEM
FUEL INJECTION (FUEL SYSTEM)
5. Control System
A: GENERAL
The ECM receives signals from various sensors, switches, and other control modules. Using these
signals, it determines the engine operating conditions and if necessary, emits signals to one or more
systems to control them for optimum operation.
Major control items of the ECM are as follow:
Fuel injection control
Ignition control
Idle air control
Fuel pump control
Canister purge control*1
Radiator fan control*2
On-board diagnosis function
*1: Canister purge control is described under EC(H4SO) -- Emission Control (Aux. Emission Con-
trol Devices) Evaporative Emission Control System.
*2: Radiator fan control is described under CO(H4SO) -- COOLING.
FU(H4SO)-28
W1860BE.book Page 29 Tuesday, January 28, 2003 11:01 PM
CONTROL SYSTEM
FUEL INJECTION (FUEL SYSTEM)
B: INPUT AND OUTPUT SIGNALS
Signal Unit Function
Input sig- Manifold absolute pressure sensor Detects the intake air pipe (absolute) pressure.
nals
Intake air temperature sensor Detects the intake air temperature.
Atmospheric pressure sensor Detects the amount of intake air (measures the atmospheric pressure).
Throttle position sensor Detects the throttle valve position.
Front oxygen (A/F) sensor Detects the density of oxygen in exhaust gases at the upstream of the front
catalytic converter.
Rear oxygen sensor Detects the density of oxygen in exhaust gases at the downstream of the
front catalytic converter.
Crankshaft position sensor Detects the crankshaft angular position.
Camshaft position sensor Detects the combustion cylinder.
Engine coolant temperature sensor Detects the engine coolant temperature.
Knock sensor Detects engine knocking.
Vehicle speed sensor Detects the vehicle speed.
Ignition switch Detects operation of the ignition switch.
Starter switch Detects the condition of engine cranking.
Neutral switch (MT) Detects that the gear is in neutral.
Inhibitor switch (AT) Detects shift positions.
Torque control signal Controls engine torque.
Heater circuit of front and rear oxygen Detects abnormality in the heater circuit of the front and rear oxygen sen-
sensors sors.
Diagnostics of TCM (AT) Detects the self-diagnostics of TCM.
A/C switch Detects ON-OFF operation of the A/C switch.
Fuel temperature sensor Detects the temperature of the fuel in the fuel tank.
Fuel tank pressure sensor Detects the evaporation gas pressure in the fuel tank.
Fuel level sensor Detects the level of the fuel in the fuel tank.
Small light switch Detects ON-OFF operation of the small light switch.
Blower fan switch Detects ON-OFF operation of the blower fan switch.
Rear defogger switch Detects ON-OFF operation of the rear defogger switch.
Output sig- Fuel injector Activates an injector.
nals
Ignition signal Turns the primary ignition current ON or OFF.
Fuel pump relay Turns ON or OFF the fuel pump relay.
A/C control relay Turns ON or OFF the A/C control relay.
Radiator fan control relay Turns ON or OFF the radiator fan control relay.
Idle air control solenoid valve Adjusts the amount of air flowing through the bypass line in the throttle
body.
Engine malfunction indicator light Indicates existence of abnormality.
Purge control solenoid valve Controls purge of evaporative gas absorbed by the canister.
Pressure control solenoid valve Controls evaporation pressure in fuel tank.
Drain valve Closes the evaporation line between the fuel tank and canister to detect
leakage of evaporation gases.
Air assist solenoid valve Adjusts the assist air flow for fuel injection.
Power supply Controls ON/OFF of the main power supply relay.
FU(H4SO)-29
W1860BE.book Page 30 Tuesday, January 28, 2003 11:01 PM
CONTROL SYSTEM
FUEL INJECTION (FUEL SYSTEM)
C: FUEL INJECTION CONTROL
The ECM receives signals from various sensors and based on them, it determines the amount of
fuel injected and the fuel injection timing. It performs the sequential fuel injection control over the
entire engine operating range except during start-up of the engine.
The amount of fuel injected depends upon the length of time the injector stays open. The fuel in-
jection duration is determined according to varying operating condition of the engine. For the pur-
pose of achieving highly responsive and accurate fuel injection duration control, the ECM performs
a new feedback control that incorporates a learning feature as detailed later.
The sequential fuel injection control is performed such that fuel is injected accurately at the time
when the maximum air intake efficiency can be achieved for each cylinder (i.e., fuel injection is com-
pleted just before the intake valve begins to open).
1. FUEL INJECTION DURATION
Fuel injection duration is basically determined as indicated below:
While cranking the engine:
The duration defined below is used.
Duration of fuel injection during engine start-up ..... Determined according to the engine coolant
temperature detected by the engine coolant temperature sensor.
During normal operation:
The duration is determined as follows:
Basic duration of fuel injection ◦ Jabse Service Manual Search 2026 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo