Daewoo CIELO EURO III Manual page 490

1F – 320 ENGINE CONTROLS
CATALYST (OXYGEN SENSOR) LOW EFFICIENCY
System Description
In order to control exhaust emissions of Hydrocarbons
(HC), Carbon Monoxide (CO) and Oxides of Nitrogen
(NOx), a three-way catalytic converter is used. The cat-
alyst within the converter promotes a chemical reaction
which oxidizes the HC and CO present in the exhaust
gas, converting them into harmless water vapor and car-
bon dioxide, and it reduces NOx, converting it into nitro-
gen. The catalytic converter also has the ability to store
oxygen. The engine
control module (ECM) has the capability to monitor this
process using a Heated Oxygen Sensor (HO2S 2) lo-
cated in the exhaust stream past the three-way catalytic
converter. The HO2S 2 produces an output signal which
indicates the oxygen storage capacity of the catalyst;
this in turn indicates the catalyst's ability to convert ex-
haust emissions effectively. The ECM monitors
the catalyst efficiency by first allowing the catalyst to
heat up, waiting for a stabilization period while the en-
gine is idling, and then adding and removing fuel while
monitoring the reaction of the HO2S 2. When the cata-
lyst is functioning properly, the HO2S 2 response to the
extra fuel is slow compared to the O2S 1. When the
HO2S 2 response is close to that of the O2S 1, the Oxy-
gen storage capability or efficiency of the catalyst is con-
sidered to be bad, and the Malfunction Indicator Lamp
(MIL) will be illuminated.
Conditions for Setting the DTC
D Oxygen storage capacity index time is less than 0.8
second.
D DTC(s) P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0125, P0131, P0132, P0133,
P0134, P0137, P0138, P0140, P0141, P0171,
P0172, P0201, P0202, P0203, P0204, P0300,
P0336, P0337, P0341, P0342, P0351, P0352,
P0402, P0404, P0405, P0406, P0502, P0506,
P0507, P0562, P1133, P1134, P1167, P1171 and
P1404 are not set.
D Before idle test, vehicle needs to be driven for at
least: 10 seconds at airflow is greater than 7 g/sec.
Oxygen sensor storage test conditions:
D At idle and Closed Loop (C/L) stoichiometry.
D The Purge concetration learned.
D The engine run time is greater than 360 seconds.
D The airflow is between 1.6 and 6.0 g/sec.
D The Throttle Position (TP) is less than 1.5%.
D The coolant temperature is between 70_C (158_F)
and 105_C (221_F).
D The Intake Air Temperature (IAT) is between –7_C
(19.4_F) and 70_C (158_F).
DIAGNOSTIC TROUBLE CODE (DTC) P0420
D The Barometric Pressure (BARO) is greater than
72.0kPa.
D The catalyst temperature is between 450_C (842_F)
and 850_C (1562_F).
D C/L integrator change is less than 0.04.
D The idle time is less than 1 minute.
D The vehicle speed is less than 2 mph (3 km/h).
D The BLM learned.
D Above stabilized for 5 seconds.
Test is aborted for this idle if:
D The change in the engine speed is greater than 100
rpm.
D A/C state changed.
D FAN state changed.
D Insufficient A/F shift.
Action Taken When the DTC Sets
D The Malfunction Indicator Lamp (MIL) will illuminate.
D The ECM will record operating conditions at the
time the diagnostic fails. This information will be
DAEWOO T-154 BL2,3