Daewoo Nubira User Manual page 609

1F – 406IENGINE CONTROLS
EVAPORATIVE EMISSION CANISTER
The Evaporative (EVAP) Emission canister is an emission
control device containing activated charcoal granules.
The EVAP emission canister is used to store fuel vapors
from the fuel tank. Once certain conditions are met, the
powertrain control module (PCM)/engine control module
(ECM) activates the EVAP canister purge solenoid, allow-
ing 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 blowby gases which are 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 following
conditions:
S
Rough idle
S
Stalling or low idle speed
S
Oil leaks
S
Oil in the air cleaner
S
Sludge in the engine
A leaking PCV hose may cause the following conditions:
S
Rough idle
S
Stalling
S
High idle speed
ENGINE COOLANT TEMPERATURE
SENSOR
The Engine Coolant Temperature (ECT) sensor is a
thermistor (a resistor which changes value based on tem-
perature) mounted in the engine coolant stream. Low cool-
ant temperature produces a high resistance (100,000
ohms at –40³F [–40³C]) while high temperature causes
low resistance (70 ohms at 266³F [130³C]).
The powertrain control module (PCM)/engine control
module (ECM) supplies 5 volts to the ECT sensor through
a resistor in the PCM/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 PCM/ECM can determine the coolant tem-
perature. The engine coolant temperature affects most of
the systems that the PCM/ECM controls. A failure in the
ECT sensor circuit should set a diagnostic trouble code
P0117 or P0118. Remember, these diagnostic trouble
codes indicate a failure in the ECT sensor circuit, so prop-
er use of the chart will lead either to repairing a wiring prob-
lem or to replacing the sensor to repair a problem properly.
THROTTLE POSITION SENSOR
The Throttle Position (TP) sensor is a potentiometer con-
nected to the throttle shaft of the throttle body. The TP sen-
sor electrical circuit consists of a 5 volt supply line and a
ground line, both provided by the powertrain control mod-
ule (PCM)/engine control module (ECM). The PCM/ECM
calculates the throttle position by monitoring the voltage
on this signal line. The TP sensor output 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 PCM/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 injec-
tor and an unstable idle, because the PCM/ECM thinks the
throttle is moving. A problem in any of the TP sensor cir-
cuits should set a diagnostic trouble code (DTC) P0121 or
P0122. Once the DTC is set, the PCM/ECM will substitute
a default value for the TP sensor and some vehicle perfor-
mance will return. A DTC P0121 will cause a high idle
speed.
CATALYST MONITOR OXYGEN
SENSORS
Three–way catalytic converters are used to control emis-
sions of hydrocarbons (HC), carbon monoxide (CO), and
oxides of nitrogen (NOx). The catalyst within the convert-
ers promotes a chemical reaction. This reaction oxidizes
the HC and CO present in the exhaust gas and converts
them into harmless water vapor and carbon dioxide. The
catalyst also reduces NOx by converting it to nitrogen. The
powertrain control module (PCM)/engine control module
(ECM) can monitor this process using the Bank 1 Sensor
1 and Bank 1 Sensor 2 sensors. These sensors produce
an output signal which indicates the amount of oxygen
present in the exhaust gas entering and leaving the three–
way converter. This indicates the catalyst's ability to effi-
ciently convert exhaust gasses. If the catalyst is operating
efficiently, the Bank 1 Sensor 1 sensor signals will be more
active than the signals produced by the Bank 1 Sensor 2
sensor. The catalyst monitor sensors operate the same
way as the fuel control sensors. The sensor's main func-
tion is catalyst monitoring, but they also have a limited role
in fuel control. If a sensor output indicates a voltage either
above or below the 450 mv bias voltage for an extended
period of time, the PCM/ECM will make a slight adjust-
ment to fuel trim to ensure that fuel delivery is correct for
catalyst monitoring.
A problem with the Bank 1 Sensor 1 sensor circuit will set
DTC P0131, P0132, P0133 or P0134 depending, on the
special condition. A problem with the Bank 1 Sensor 2 sen-
sor signal will set DTC P0137, P0138, P0140 or P0141,
depending on the special condition.
DAEWOO V–121 BL4