Evaporative Emission Canister; Positive Crankcase Ventilation Control System Operation; Engine Coolant Temperature Sensor; Throttle Position Sensor - Daewoo CIELO EURO III Manual

1F – 412 ENGINE CONTROLS
tions determined by mass airflow, fuel trim, and intake
air temperature.
Poor idle, stalling, and poor driveability can be caused
by the following conditions:
D An inoperative EVAP emission canister purge valve.
D A damaged canister.
D Hoses that are split, cracked, or not connected to the
proper tubes.

EVAPORATIVE EMISSION CANISTER

The evaporative (EVAP) emission canister is an emis-
sion control device containing activated charcoal gran-
ules. The EVAP emission canister is used to store fuel
vapors from the fuel tank. Once certain conditions are
met, the engine con-
trol module (ECM) activates the EVAP emission canister
purge solenoid, allowing the fuel vapors to be drawn into
the engine cylinders and burned.
POSITIVE CRANKCASE
VENTILATION CONTROL SYSTEM
OPERATION
A Positive Crankcase Ventilation (PCV) system is used
to provide complete use of the crankcase vapors. Fresh
air from the air cleaner is supplied to the crankcase. The
fresh air is mixed with blow-by gases and is then passed
through a vacuum hose into the intake manifold.
Periodically inspect the hoses and the clamps. Replace
any crankcase ventilation components as required.
A restricted or plugged PCV hose may cause the follow-
ing conditions:
D Rough idle.
D Stalling or low idle speed.
D Oil leaks.
D Oil in the air cleaner.
D Sludge in the engine.
A leaking PCV hose may cause the following conditions:
D Rough idle.
D Stalling.
D High idle speed.
ENGINE COOLANT TEMPERATURE
SENSOR
The Engine Coolant Temperature (ECT) sensor is a
thermistor (a resistor which changes value based on
temperature) mounted in the engine coolant stream.
Low coolant temperature produces a high resistance
(100,000 ohms at *40_C [*40_F]) while high tempera-
ture causes low resistance (70 ohms at 130_C [266_F]).
The engine control
module (ECM) supplies 5 volts to the coolant tempera-
ture sensor through a resistor in the ECM and
measures the change in voltage. The voltage will be
high when the engine is cold and low when the engine is
hot. By measuring the change in voltage, the ECM
can determine the coolant temperature. The engine
coolant temperature affects most of the systems that the
ECM controls. A failure in the coolant sensor cir-
cuit should set a diagnostic trouble code P0117 or
P0118. Remember, these diagnostic trouble codes indi-
cate a failure in the coolant temperature circuit, so prop-
er use of the chart will lead either to repairing a wiring
problem or to replacing the sensor to repair a problem
properly.

THROTTLE POSITION SENSOR

The Throttle Position (TP) sensor is a potentiometer
connected to the throttle shaft of the throttle body. The
TP sensor electrical circuit consists of a 5 volt supply
line and a ground line, both provided by the
engine control module (ECM).
The ECM calculates the throttle position by moni-
toring the voltage on this signal line. The TP sensor out-
put changes as the accelerator pedal is moved,
changing the throttle valve angle. At a closed throttle
position, the output of the TP sensor is low, about 0.5
volt. As the throttle valve opens, the output increases so
that, at wide open throttle (WOT), the output voltage will
be about 5 volts.
The ECM can determine fuel delivery based on
throttle valve angle (driver demand). A broken or loose
TP sensor can cause intermittent bursts of fuel from the
injector and an unstable idle, because the ECM
senses the throttle is moving. A problem in any of the TP
sensor circuits should set a diagnostic trouble code
P0122 or P0123. Once the diagnostic trouble code is
set, the ECM will substitute a default value for the
TP sensor and some vehicle performance will return.
DAEWOO T-154 BL2,3