System Overview - Subaru LEGACY 2002 Quick Reference Index

Emission Control (Aux. Emission Control Devices)

1. System Overview

There are three emission control systems which are as follows:
! Crankcase emission control system
! Exhaust emission control system
! Three-way catalyst system
! Air/fuel (A/F) control system
! Ignition control system
! Evaporative emission control system
Item
Crankcase emission control
system
Exhaust Catalyst Front
emis- system
Rear
sion
control A/F control
system
system
Ignition control
system
Evaporative emission control
system
SYSTEM OVERVIEW
Main components
Positive crankcase ventilation
(PCV) valve
Three-way catalyst
Engine control module (ECM)
Front oxygen (A/F) sensor
Rear oxygen sensor
Throttle position sensor
Intake air temperature and
pressure sensor
ECM
Crankshaft position sensor
Camshaft position sensor
Engine coolant temperature
sensor
Knock sensor
Canister
Purge control solenoid valve
Function
Draws blow-by gas into intake manifold from crankcase and
burns it together with air-fuel mixture. Amount of blow-by gas to
be drawn in is controlled by intake manifold pressure.
Oxidizes HC and CO contained in exhaust gases as well as re-
ducing NOx.
Receives input signals from various sensors, compares signals
with stored data, and emits a signal for optimal control of air-
fuel mixture ratio.
Detects quantity of oxygen contained exhaust gases.
Detects density of oxygen contained exhaust gases.
Detects throttle position.
Detects absolute pressure of intake manifold.
Detects intake air temperature of intake manifold.
Receives various signals, compares signals with basic data
stored in memory, and emits a signal for optimal control of igni-
tion timing.
Detects engine speed (Revolution).
Detects reference signal for combustion cylinder discrimina-
tion.
Detects coolant temperature.
Detects engine knocking.
Absorbs evaporative gas which occurs in fuel tank when engine
stops, and releases it to combustion chambers for a complete
burn when engine is started. This prevents HC from being dis-
charged into atmosphere.
Receives a signal from ECM and controls purge of evaporative
gas absorbed by canister.
EC-2