1F – 484IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0420
CATALYST OXYGEN SENSOR LOW EFFICIENCY
Circuit Description
In order to control exhaust emissions of Hydrocarbons
(HC), Carbon Monoxide (CO) and Nitrogen Oxide (NOx),
a Three–Way Catalytic Converter (TWC) 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 carbon
dioxide, it also reduces NOx, converting it into nitrogen.
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
Rear Heated Oxygen Sensor (HO2S2) located in the ex-
haust stream past the TWC. The HO2S2 produces an out-
put signal which indicates the oxygen storage capacity of
the catalyst; this in turn indicates the catalyst’s ability to
convert exhaust emissions effectively. The ECM monitors
the catalyst efficiency by first allowing the catalyst to heat
up, waiting for a stabilization period while the engine is id-
ling, and then adding and removing fuel while monitoring
the reaction of the HO2S2. When the catalyst is function-
ing properly, the HO2S2 response to the extra fuel is slow
compared to the Front Heated Oxygen Sensor (HO2S1).
When the HO2S2 response is close to that of the HO2S1,
the Oxygen storage capability or efficiency of the catalyst
is considered to be bad, and the Malfunction Indicator
Lamp (MIL) will illuminate.
Conditions for Setting the DTC
S Oxygen storage capacity index time is less than 0.3
seconds.
S Before idle test, the vehicle needs to be driven for
at least:
S 15 seconds at airflow is greater than 9.2 g/sec.
for manual transaxle.
S 11 seconds at airflow is greater than 12 g/sec
for automatic transaxle.
S Oxygen Sensor Capacity test condition:
S Closed loop stoichiometry.
S Purge concentration learned.
S Engine is running more than 330 seconds.
S Airflow is between 2.5 and 7.25 g/sec.
S Throttle Position (TP) sensor is less than 1.5%.
S Intake Air Temperature (IAT) is between –7°C
(19.4°F) and 105°C (221°F).
S Barometric pressure (BARO) is greater than 72 kPa
(10.4 psi).
S Catalyst temperature is between 500°C (932°F)
and 850°C (1562°F) for automatic transaxle.
S Catalyst temperature is between 450°C (842°F)
and 850°C (1562°F) for automatic transaxle.
S Closed Loop integrator change is less than 0.03.
S Idle time is less than 1 minute.
S Vehicle speed is less than 3 km/h (1.9 mph).S Block Learn Mode is learned.
S Above condition is stabilized for 5 seconds.
Note : Test is aborted for this idle if:
S Change in engine speed is greater than 80 rpm.
S A/C status changed.
S Cooling fan status changed.
S Insufficient air/fuel shift.
S DTC(s) P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0131, P0132, P0133, P1133,
P0134, P0135, P0137, P0138, P0140, P0141,
P1167, P1171, P0171, P0172, P0201, P0202,
P0203, P0204, P0300, P0336, P0337, P0341,
P0342, P0351, P0352, P0402, P0404, P1404,
P0405, P0406, P0443, P0502, P0506, P0507, and
P0562 are not set.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illumi-
nate.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
The catalyst test may abort due to a change in the engine
load. Do not change the engine load (i.e. A/C, coolant fan,
heater motor) while a catalyst test is in progress.
An intermittent problem may be caused by a poor connec-
tion, rubbed–through wire insulation, or a wire that is bro-
ken inside the insulation.
Any circuitry, that is suspected as causing the intermittent
complaint, should be thoroughly checked for the following
conditions:
S Backed–out terminals
S Improper mating
S Broken locks
S Improperly formed
S Damaged terminals
S Poor terminal–to–wire connection
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic Table.
ENGINE CONTROLS 1F – 485
DAEWOO V–121 BL4
1. The On–Board Diagnostic (EOBD) System Check
prompts the technician to complete some basic
checks and store the freeze frame and failure re-
cords data on the scan tool if applicable. This
creates an electronic copy of the data taken when
the malfunction occurred. The information is then
stored on the scan tool for later reference.
2. If any component DTCs are set, diagnose those
DTCs first. A fault in a component can cause the
converter to appear degraded or may have caused
its failure.
3. This step includes checks for conditions that can
cause the three–way catalytic converter to appear
degraded. Repair any problems found before pro-
ceeding with this table.
5. If the three–way catalytic converter needs to be
replaced, make sure that another condition is not
present which would cause the converter to be-
come damaged. These conditions may include thefollowing: misfire, high engine oil or coolant con-
sumption, and/or retarded spark timing or weak
spark. To avoid damaging the replacement convert-
er, correct any possible causes of converter dam-
age before replacing the catalytic converter.
6. Clearing DTCs allows the catalyst test to be run up
to 6 times this ignition cycle. Once the ignition is
cycled, the test will run only once. Driving the ve-
hicle heats the catalyst to a test temperature. The
ECM must see predetermined amount of time at
above idle before allowing the catalyst test to run at
idle. Once at idle, the ECM will allow the system to
stabilize and then test the catalyst in 2 stages.
7. If no faults have been found at this point and no
additional DTCs were set, refer to ”Diagnostic Aids”
in this section for additional checks and informa-
tion.
DTC P0420 – Catalyst Oxygen Sensor Low Efficiency
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) System
Check.
Was the check performed?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
2S Install a scan tool to the Data Link Connector
(DLC).
S Turn the ignition ON.
Are any component Diagnostic Trouble Codes
(DTCs) set?–Go to
applicable DTC
tablesGo to Step 3
3Visually/physically check the following:
S Exhaust system for a leak.
S Rear Heated Oxygen Sensor (HO2S2)
Is a problem found?–Go to Step 4Go to Step 5
4Repair the exhaust system as needed.
Is the repair complete?–Go to Step 6–
5Replace the Three Way Catalytic Converter (TWC).
Is the repair complete?–Go to Step 6–
61. Using the scan tool, clear the Diagnostic
Trouble Codes (DTCs).
2. Start the engine and idle at normal operating
temperature.
3. Operate the vehicle within the Conditions for
setting this DTC as specified in the supporting
text.
Does the scan tool indicate that this diagnostic has
run and passed?–Go to Step 7Go to Step 2
7Check if any additional DTCs are set.
Are any DTCs displayed that have not been diag-
nosed?–Go to
Applicable DTC
tableSystem OK
1F – 486IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0443
EVAPORATIVE EMISSION SYSTEM PURGE SOLENOID
CONTROL CIRCUIT
System Description
The Evaporative Emission (EVAP) system includes the
following components:
S Fuel tank
S Fuel tank pressure sensor.
S Fuel pipes and hoses.
S Fuel vapor lines.
S Fuel cap
S EVAP canister.
S Purge lines.
S EVAP emission canister purge solenoid valve.
S EVAP service port.
The EVAP purge canister solenoid is controlled by the En-
gine Control Module (ECM). The ECM applies a ground to
the EVAP purge canister solenoid. The ECM determines
when to activate the EVAP canister purge solenoid de-
pending on operating conditions, including Throttle Posi-
tion (TP), engine speed, Engine Coolant Temperature
(ECT) and ambient temperature.
The Diagnostic Trouble Code will detect an open or short
circuit.
Conditions for Setting the DTC
S Ignition ON.
S Ignition voltage is greater than 11 v.
Action Taken When the DTC SetsS The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive trip with a fail.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using a scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Using Freeze Frame and/or Failure Records data may aid
in locating an intermittent condition. If the DTC cannot be
duplicated, the information included in the Freeze Frame
and/or Failure Records data can be useful in determining
how many miles since the DTC set. The Fail Counter and
the Pass Counter can also be used to determine how
many ignition cycles the diagnostic reported a pass and/or
a fail. Operate the vehicle within the same freeze frame
conditions (rpm, load, vehicle speed, temperature, etc.)
that were noted. This will isolate when the DTC failed.
1F – 498IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0502
VEHICLE SPEED SENSOR NO SIGNAL (ENGINE SIDE)
Circuit Description
Vehicle speed information is provided to the Engine Con-
trol Module (ECM) by the Vehicle Speed Sensor (VSS).
The VSS is a permanent magnet generator that is
mounted in the transaxle and produces a pulsing voltage
whenever vehicle speed is over 3 mph (5 km/h). The Alter-
nating Current (AC) voltage level and the number of
pulses increases with vehicle speed. The ECM converts
the pulsing voltage into mph (km/h) and then supplies the
necessary signal to the instrument panel for speedometer/
odometer operation and to the cruise control module and
multi–function alarm module operation. This Diagnostic
Trouble Code (DTC) will detect if vehicle speed is reason-
able according to engine rpm and load.
Conditions for Setting the DTC
S Vehicle speed is less than 5 km/h (3.1 mph) for
Power and Decel test.
S Engine is running.
S Engine Coolant Temperature (ECT) is greater than
60 °C (140 °F).
S Ignition voltage is between 11–16 volts.
S Power Test
S The rpm is between 1200 and 4000.S Throttle Position (TP) sensor is between 25%
and 60%.
S MAP is greater than 60 kPa (8.7 psi).
S Deceleration Test
S Generator compensated Manifold Absolute
Pressure (MAP) is less than 30 kPa (4.4 psi)
S Change in rpm per cycle is less than 50 rpm/
cycle.
S Throttle Position (TP) sensor is less than 0.8%.
S The rpm is between 1800 and 6000.
S DTC(s) P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0201, P0202, P0203, P0204,
P0300, P0351, P0352, P0402, P0404, P1404,
P0405, and P0406 are not set.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive trip with a fail.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.
Conditions for Clearing the MIL/DTC
ENGINE CONTROLS 1F – 501
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0506
IDLE SPEED RPM LOWER THAN DESIRED IDLE SPEED
Circuit Description
The Engine Control Module (ECM) controls the air enter-
ing into the engine with an Idle Air Control (IAC) Valve. To
increase the idle rpm, the ECM commands the pintle in-
side the IAC valve away from the throttle body seat. This
allows more air to bypass through the throttle blade. To de-
crease the rpm the ECM commands the pintle towards the
throttle body seat. This reduces the amount of air bypass-
ing the throttle blade. A scan tool will read the IAC valve
pintle position in counts. The higher the counts, the more
air that is allowed to bypass the throttle blade. This Diag-
nostic Trouble Code (DTC) determines if a low idle condi-
tion exists as defined as 100 rpm below the desired idle
rpm.
Conditions for Setting the DTC
S No intrusive tests are active.
S DTC(s) P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0131, P0132,
P0133, P0135, P0141, P1133, P1134, P0171,
P01167, P1171, P0172, P0201, P0202, P0203,
P0204, P0300, P0336, P0337, P0341, P0342,
P0351, P0352, P0402, P0404, P1404, P0405,
P0406, P0443, and P0502 are not set.
S Engine is running more than 60 seconds.
S Barometric Pressure (BARO) is greater than 72
kPa (10.4 psi).
S Engine Coolant Temperature (ECT) is greater than
60°C (140°F).
S Ignition voltage is between 11 and 16 volts.
S Manifold Absolute Pressure is less than 60 kPa (8.7
psi).
S IAC valve is controlled fully opened.
S All of the above must be met for greater than 5 sec-
onds.Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive ignition cycle with a fail.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Inspect the IAC valve electrical connection for proper mat-
ing.
Inspect the wiring harness for damage.
Inspect the throttle stop screw for signs of tampering.
Inspect the throttle linkage for signs of binding or exces-
sive wear.
A slow or unstable idle may be caused by one of the follow-
ing conditions:
S Fuel system too rich or too lean.
S Foreign material in the throttle body bore or in the
air induction system.
S A leaking or restricted intake manifold.
S Excessive engine overloading. Check for seized
pulleys, pumps, or motors on the accessory drive.
S Overweight engine oil.
1F – 504IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0507
IDLE SPEED RPM HIGHER THAN DESIRED IDLE SPEED
Circuit Description
The Engine Control Module (ECM) controls the air enter-
ing into the engine with an Idle Air Control (IAC) Valve. To
increase the idle rpm, the ECM commands the pintle in-
side the IAC valve away from the throttle body seat. This
allows more air to bypass through the throttle blade. To de-
crease the rpm the ECM commands the pintle towards the
throttle body seat. This reduces the amount of air bypass-
ing the throttle blade. A scan tool will read the IAC valve
pintle position in counts. The higher the counts, the more
air that is allowed to bypass the throttle blade. This Diag-
nostic Trouble Code (DTC) determines if a high idle condi-
tion exists as defined as 200 rpm above the desired idle
rpm.
Conditions for Setting the DTC
S No intrusive tests are active.
S DTC(s) P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0131, P0132,
P0133, P0135, P0141, P1133, P1134, P0171,
P1167, P1171, P0172, P0201, P0202, P0203,
P0204, P0300, P0336, P0337, P0341, P0342,
P0351, P0352, P0402, P0404, P1404, P0405,
P0406, P0441, P0443, and P0502 are not set.
S Engine is running more than 60 seconds.
S Barometric Pressure (BARO) is greater than 72
kPa (10.4 psi).
S Engine Coolant Temperature (ECT) is greater than
60°C (140°F).
S Ignition voltage is between 11 and 16 volts.
S The Intake Air Temperature (IAT) is greater than
–20°C (–4°F).
S IAC valve is controlled fully closed.S All of the above must be met for greater than 5 sec-
onds.
S Idle engine speed error is greater than 200 rpm for
10 seconds.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive ignition cycle with a fail.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Inspect the IAC valve electrical connection for proper mat-
ing.
Inspect the wiring harness for damage.
Inspect the throttle stop screw for signs of tampering.
Inspect the throttle linkage for signs of binding or exces-
sive wear.
Inspect the positive crankcase ventilation (PCV) valve and
PCV hose.
A slow or unstable idle may be caused by one of the follow-
ing conditions:
ENGINE CONTROLS 1F – 507
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0532
A/C PRESSURE SENSOR LOW VOLTAGE
Circuit Description
The Air Conditioning (A/C) system uses an A/C refrigerant
pressure sensor mounted in the high pressure side of the
A/C refrigerant system to monitor A/C refrigerant pres-
sure. The Engine Control Module (ECM) uses this infor-
mation to turn ON the engine coolant fans when the A/C
refrigerant pressure is high and to keep the compressor
disengaged when A/C refrigerant pressure is excessively
high or low.
The Air Conditioning Pressure (ACP) sensor operates like
other 3–wire sensors. The ECM applies a 5.0 volt refer-
ence and a sensor ground to the sensor. Changes in the
A/C refrigerant pressure will cause the ACP sensor input
to the ECM to vary. The ECM monitors the ACP sensor
signal circuit and can determine when the signal is outside
of the possible range of the sensor. When the signal is out
of range for a prolonged period of time, the ECM will not
allow the A/C compressor clutch to engage. This is done
to protect the compressor.
Conditions for Setting the DTC
S A/C pressure is less than 1 % of the sensor reading
scale.
S Engine is running.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will not illumi-
nate.S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Failure Records buffers.
S A history DTC is stored.
S The A/C compressor operation will be disabled
while the low voltage indication exists.
Conditions for Clearing the MIL/DTC
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Inspect harness connectors for backed–out terminals, im-
proper mating, broken locks, improperly formed or dam-
aged terminals, and poor terminal–to–wire connection at
the ECM.
Inspect the wiring harness for damage. If the harness ap-
pears to be OK, observe the A/C pressure display on the
scan tool while moving the connectors and wiring har-
nesses related to the A/C Pressure sensor. A change in
the A/C pressure display will indicate the location of the
fault.
If DTC P0532 cannot be duplicated, reviewing the Fail Re-
cords vehicle mileage since the diagnostic test last failed
may help determine how often the condition that caused
the DTC to set occurs. This may assist in diagnosing the
condition.
1F – 510IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0533
A/C PRESSURE SENSOR HIGH VOLTAGE
Circuit Description
The Air Conditioning (A/C) system uses an A/C refrigerant
pressure sensor mounted in the high pressure side of the
A/C refrigerant system to monitor A/C refrigerant pres-
sure. The Engine Control Module (ECM) uses this infor-
mation to turn ON the engine coolant fans when the A/C
refrigerant pressure is high and to keep the compressor
disengaged when A/C refrigerant pressure is excessively
high or low.
The Air Conditioning Pressure (ACP) sensor operates like
other 3–wire sensors. The ECM applies a 5.0 volt refer-
ence and a sensor ground to the sensor. Changes in the
A/C refrigerant pressure will cause the ACP sensor input
to the ECM to vary. The ECM monitors the ACP sensor
signal circuit and can determine when the signal is outside
of the possible range of the sensor. When the signal is out
of range for a prolonged period of time, the ECM will not
allow the A/C compressor clutch to engage. This is done
to protect the compressor.
Conditions for Setting the DTC
S A/C pressure is greater than 99% of the sensor
reading scale.
S Engine is running.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will not illumi-
nate.S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Failure Records buffers.
S A history DTC is stored.
S The A/C compressor operation will be disabled
while the high voltage indication exists.
Conditions for Clearing the MIL/DTC
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Inspect harness connectors for backed–out terminals, im-
proper mating, broken locks, improperly formed or dam-
aged terminals, and poor terminal–to–wire connection at
the ECM.
Inspect the wiring harness for damage. If the harness ap-
pears to be OK, observe the A/C pressure display on the
scan tool while moving the connectors and wiring har-
nesses related to the ACP sensor. A change in the A/C
pressure display will indicate the location of the fault.
If DTC P0533 cannot be duplicated, reviewing the Fail Re-
cords vehicle mileage since the diagnostic test last failed
may help determine how often the condition that caused
the DTC to set occurs. This may assist in diagnosing the
condition.