EMISSION CONTROL
TSB Revision
ENGINE AND EMISSION CONTROL
17-107
EVAPORATIVE EMISSION CONTROL SYSTEM
GENERAL DESCRIPTION (EVAPORATIVE EMISSION SYSTEM)
M1173005100416
The evaporative emission (EVAP) system prevents
fuel vapors generated in the fuel tank from escaping
into the atmosphere.
Fuel vapors from the fuel tank flow through the vapor
pipe/hose to be stored temporarily in the EVAP can-
ister. When the vehicle is in operation, fuel vapors
stored in the EVAP canister flow through the EVAP
purge solenoid, purge port and intake manifold ple-
num to the combustion chamber.
When the engine coolant temperature is low or when
the intake air quantity is small (when the engine is at
idle, for example), the powertrain control module
(PCM) brings the EVAP purge solenoid into the OFF
state to shut off the fuel vapor flow to the intake man-
ifold plenum. This ensures the driveability when the
engine is cold or running under low load and also
stabilizes the emission level.
An EVAP ventilation solenoid is provided between
the EVAP canister and atmosphere, and used to
monitor for OBD-II EVAP leaks. This solenoid is nor-
mally OFF. However, it turns ON when monitoring the
OBD-II EVAP leaks and shuts off the atmosphere
flow to the EVAP canister. Then the fuel tank differ-
ential pressure sensor monitors the fuel vapor pres-
sure to detect OBD-II EVAP leaks. The fuel overflow
limiter valve and the leveling valve prevent fuel from
being overfilled. The fuel cut off valve prevents fuel
leaks if the vehicle is rolled over in an accident.
The EVAP ventilation valve releases the air from the
fuel tank through the EVAP canister into the atmo-
sphere when the fuel tank pressure increases due to
refueling, etc. The EVAP ventilation valve and the air
filter supply the atmospheric air to the EVAP canister
when the fuel tank pressure decreases.
SYSTEM DIAGRAM
AK300573
FUEL TANK DIFFERENTIAL
PRESSURE SENSOR
LIQUID SEPARATOR
EVAPORATIVE
EMISSION
CANISTER
EVAPORATIVE
EMISSION
PURGE
SOLENOID
ON: OPEN
PCM
INTAKE AIR TEMPERATURE
SENSOR
ENGINE COOLANT
TEMPERATURE SENSOR
VOLUME AIRFLOW SENSOR
FUEL
TANK
MFI RELAY
FUEL OVERFLOW
LIMITER VALVE
FUEL CUT
OFF VALVE
LEVELING VALVE
EVAPORATIVE EMISSION
VENTILATION VALVE
AIR FILTER
EVAPORATIVE EMISSION
VENTILATION SOLENOID
ON: CLOSED
AC
BAROMETRIC PRESSURE
SENSOR