Chrysler laser 1990 Technical Information Manual page 380

EMISSION CONTROL SYSTEMS
OPERATION <California>
The engine control unit functions to calculate the
engine load, based upon the intake air volume
signals (from the air-flow sensor) and the rpm
signals (from the crank-angle sensor), and the EGR
control solenoid valve is activated according to the
engine load. The EGR amount is then regulated
according to the engine load calculated in this way.
Load a Intake air volume/Engine rpm
If, however, the engine coolant temperature is low,
the actuation duty is attenuated, the EGR control
valve activation negative pressure (vacuum) is
leaked from the throttle body A port, thus reducing
or interrupting the EGR flow volume and thereby
maintaining driveability during cold.
When, as a result of clogging of the EGR cant'
valve or as a result of an operational malfunctio,.,
the EGR flow volume decreases, the EGR gas
temperature downstream. from the EGR control
valve decreases. The engine control unit functions
to detect the operation conditions of the EGR
system by this characteristic.
The temperature of the EGR gas is detected by the
the EGR control valve; when the temperature
decreases to a low level, the engine warning light
(malfunction indicator light) illuminates in order to
advise the driver that a malfunction has occurred in
the EGR system.
EGR control
solenoid valve
EGR contc
Engine control unit
Control
relay
Engine
warning
light