Catalyst Monitor Oxygen Sensors; Exhaust Gas Recirculation Valve; Knock Sensor; G Sensor - Daewoo CIELO EURO III Manual

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
converters 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.
gine control module (ECM) can monitor this process us-
ing 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 enter-
ing and leaving the three-way converter. This indicates
the catalyst's ability to efficiently 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 sensors' main function is cata-
lyst 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 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 sensor signal will set DTC P0137, P0138, P0140 or
P0141 depending on the special condition.
A fault in the heated oxygen sensor heater element or its
ignition feed or ground will result in lower oxygen sensor
response. This may cause incorrect catalyst monitor
diagnostic results.
EXHAUST GAS RECIRCULATION
VALVE
The Exhaust Gas Recirculation (EGR) system is used
on engines to lower NOx (oxides of nitrogen) emission
levels caused by high combustion temperature. The
EGR valve is a duty control linear type that is operated
by the engine control
module (ECM). The EGR valve feeds small amounts of
exhaust gas into the intake manifold to decrease com-
bustion temperature. The amount of exhaust gas recir-
culated is controlled by variations in vacuum and
exhaust back pressure. If too much exhaust gas enters,
combustion will not take place. For this reason, very little
exhaust gas is allowed to pass through the valve, espe-
cially at idle.
The EGR valve is usually open under the following con-
ditions:
D Warm engine operation.
D Above idle speed.
DAEWOO T-154 BL2,3
Results of Incorrect Operation
Too much EGR flow tends to weaken combustion, caus-
ing the engine to run roughly or to stop. With too much
EGR flow at idle, cruise, or cold operation, any of the fol-
lowing conditions may occur:
D The engine stops after a cold start.
D The engine stops at idle after deceleration.
D The vehicle surges during cruise.
D Rough idle.
The en-
If the EGR valve stays open all the time, the engine may
not idle. Too little or no EGR flow allows combustion
temperatures to get too high during acceleration and
load conditions. This could cause the following condi-
tions:
D Spark knock (detonation).
D Engine overheating.
D Emission test failure.

KNOCK SENSOR

The knock sensor detects abnormal knocking in the en-
gine.
The sensor is mounted in the engine block near the cyl-
inders.
The sensor produces an AC output voltage which in-
creases with the severity of the knock. This signal is
sent to the
control module (ECM). The ECM then adjusts the
ignition timing to reduce the spark knock.

G SENSOR

The engine control
module (ECM) receives rough road information from the
G sensor. The ECM uses the rough road informa-
tion to enable or disable the misfire diagnostic. The mis-
fire diagnostic can be greatly affected by crankshaft
speed variations caused by driving on rough road sur-
faces. The G sensor generates rough road information
by producing a signal which is proportional to the move-
ment of a small metal bar inside the sensor.
If a fault occurs which causes the ECM to not re-
ceive rough road information between 30 and 80 mph
(50 and 132 km/h), DTC P1391 will set.
INTAKE AIR TEMPERATURE
SENSOR
The Intake Air Temperature (IAT) sensor is a thermistor,
a resistor which changes value based on the tempera-
ture of the air entering the engine. Low temperature pro-
duces a high resistance (100,000 ohms at *40_C
[*40_F]), while high temperature causes a low resist-
ance (70 ohms at 130_C [266_F]).
The engine control
module (ECM) provides 5 volts to the IAT sensor
ENGINE CONTROLS 1F – 413
engine