Map DAEWOO LACETTI 2004 Service Workshop Manual

1F – 404IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0172
FUEL TRIM SYSTEM TOO RICH
System Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a Closed Loop air/fuel
metering system is used. While in Closed Loop, the En-
gine Control Module (ECM) monitors the Front Heated
Oxygen Sensor (HO2S1) signal voltage and adjusts fuel
delivery based on signal voltage. A change made to fuel
delivery will be indicated by the long and short term fuel
trim values which can be monitored with the scan tool.
Ideal fuel trim values are around 128 (0%). If the HO2S1
signal is indicating a lean condition, the ECM will add fuel
resulting in fuel trim values above 128 (0% to 100%). If a
rich condition is detected, the fuel trim values will be below
128 (0% to –100%), indicating that the ECM is reducing
the amount of fuel delivered. If exhaust emissions reach
an excessive level due to a lean or rich condition, a fuel
trim Diagnostic Trouble Code (DTC) is set.
Conditions for Setting the DTC
S The average of adaptive index multiplier value is
less than 0.75.
S No intrusive tests active.
S DTCs P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0131, P0132,
P0133, P0134, P0135, P1167, P1171, P0336,
P0337, P0341, P0342, P0402, P0404, P1404,
P0405, P0406, P0443, P0506, and P0507 are not
set.
S Throttle Position (TP) is less than 95%.
S Engine speed is between 700 and 6000 rpm.
S Barometric Pressure (BARO) is greater than 72.0
kPa (10.4 psi).
S Coolant temperature is between 70°C (158°F) and
11 5°C (239°F).
S Manifold Absolute Pressure (MAP) is between 25
kPa (3.6 psi) and 99.7 kPa (14.5 psi).
S Intake Air Temperature (IAT) is between –40°C
(–40°F) and 120°C (248°F).
S Airflow is between 1.5 and 45 g/sec.
S Vehicle speed is less than 140 km/h (87 mph).
S System is in closed loop.
S Adaptive index is ready.
S System voltage is greater than 11 volts.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after two consecutive ignitions cycle in which the
diagnostic runs with the fault active (SOHC).
S The Malfunction Indicator Lamp (MIL) will illuminate
after first consecutive ignitions cycle (DOHC).
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 two consecutive ignition
cycles in which the diagnostic runs without a fault
within the freeze frame conditions that the DTC
failed.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S The DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Important : After repairs, use the scan tool Fuel Trim Re-
set function to reset the long–term fuel trim to 128 (0%).
Check for poor connection at the ECM. Inspect the har-
ness connectors 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.
Inspect the wiring harness for damage. If the harness ap-
pears to be OK, observe the HO2S1 display on the scan
tool while moving the connectors and the wiring harness
related to the engine harness. A change in the display will
indicate the location of the fault.
If a DTC P1404 is also set, check the 5 volt reference cir-
cuits for a short to voltage.
Check for a restricted exhaust system.
A shorted 5 volt reference circuit may cause a DTC P0172
to set. Check the 5 volt reference sensors for abnormal
readings.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic Table.
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.
5. A clogged air cleaner filter element restricts the air-
flow coming into the engine. This step checks the
condition of the air cleaner filter.
17. A leaky injector can cause a rich condition and set
DTC P0172. Refer to ”Fuel Injector Balance Test”
in this section.
19. A loose TP sensor may not set a TP sensor related
DTC, but may cause the system to become rich by
a higher–than–actual TP reading.

1F – 406IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
111. Turn the ignition OFF.
2. Disconnect the Manifold Absolute Pressure
(MAP) sensor electrical connector.
3. Start the engine.
4. Operate the vehicle in Closed Loop while moni-
toring the Long Term Fuel Trim value.
Does the Long Term Fuel Trim value increase above
the specified value?–20%Go to Step 20Go to Step 12
12Check the IAC valve performance. Refer to ”DTC
P0506 Idle Speed RPM Lower Than Desired Idle
Speed” or ”DTC P0507 Idle Speed RPM Higher
Than Desired Idle Speed”in this section and repair
as necessary.
Is the repair complete?–Go to Step 21Go to Step 13
131. Disconnect the vacuum hose from the fuel
pressure regulator and inspect the hose for the
presence of fuel.
2. If fuel is presence in the vacuum hose, replace
the fuel pressure regulator.
Is the repair complete?–Go to Step 21Go to Step 14
141. Turn the ignition ON.
2. Slowly press the acceleration pedal.
Does the Throttle Position (TP) sensor display in-
crease steady and evenly from its minimum voltage
at closed throttle to its maximum voltage at Wide–
Open Throttle (WOT).–Go to Step 15Go to Step 19
151. Perform the Fuel System Diagnosis.
2. If the table isolate a problem, repair as needed.
Is the repair complete?–Go to Step 21Go to Step 16
161. Perform the Evaporative Emission (EVAP)
Control System Diagnosis.
2. If the table isolate a problem, repair as needed.
Is the repair complete?–Go to Step 21Go to Step 17
171. Perform the Fuel Injector Balance Test.
2. If the table isolate a problem, repair as needed.
Is the repair complete?–Go to Step 21Go to Step 18
181. Remove the Front Heated Oxygen Sensor
(HO2S1).
2. Visually/physically inspect the HO2S1 for sili-
cone contamination.
Note : this will be indicated by a powdery white de-
posit on the portion of the HO2S1 exposed to the ex-
haust stream.
1. If contamination is present on the HO2S1, find
the source and repair as needed.
Is the repair complete?–Go to Step 21Go to
”Diagnostic
Aids”
191. Check the TP sensor mounting screws.
2. If they are too loose or missing tighten or re-
place them as needed.
3. If the screws are OK, replace the TP sensor.
Is the repair complete?–Go to Step 21–

ENGINE CONTROLS 1F – 407
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
201. Turn the ignition OFF.
2. Replace the MAP sensor.
Is the repair complete?–Go to Step 21–
211. 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 22Go to Step 2
22Check if any additional DTCs are set.
Are any DTCs displayed that have not been diag-
nosed?–Go to applica-
ble DTC tableSystem OK

ENGINE CONTROLS 1F – 455
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0337
58X CRANK POSITION SENSOR NO SIGNAL
Circuit Description
The 58X reference signal is produced by the Crankshaft
Position (CKP) sensor. During one crankshaft revolution,
58 crankshaft pulses will be produced. The Engine Control
Module (ECM) uses the 58X reference signal to calculate
engine rpm and CKP. The ECM constantly monitors the
number of pulses on the 58X reference circuit and
compares them to the number of Camshaft Position
(CMP) signal pulses being received. If the ECM does not
receive any 58X reference pulses on the 58X reference
circuit while cranking, Diagnostic Trouble Code (DTC)
P0337 will set.
Conditions for Setting the DTC
S 58X reference pulse not seen during cranking.
S DTCs P0341 and P0342 are not set.
S Change in voltage drop is greater than 0.5 volts and
change in Manifold Absolute Pressure (MAP) is
greater than 0.05kPa (0.07 psi).
S 58X reference pulse not seen for 0.078 seconds.
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
buffer.
S A history DTC is stored.
Conditions for Clearing the MIL/DTCS The MIL will turn OFF after four consecutive igni-
tion cycles in which the diagnostic runs without a
fault.
S A history DTC will clear after 40 consecutive warm–
up cycles have occurred without a fault.
S The DTC(s) can be cleared using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed–through wire insulation or a wire broken inside the
insulation. Check for:
S Poor connection – Inspect the ECM harness and
connectors for improper mating, broken locks, im-
properly formed or damaged terminals, and poor
terminal–towire connections.
S Damaged harness – Inspect the wiring harness for
damage. If the harness appears to be OK, discon-
nect the ECM, turn the ignition ON and observe a
voltmeter connected to the 58X reference circuit at
the ECM harness connector while moving the con-
nectors and the wiring harnesses related to the
ECM. A change in voltage will indicate the location
of the fault.
S Reviewing the Failure Records vehicle mileage
since the diagnostic test last failed may help deter-
mine how often the condition that caused the DTC
to be set occurs. This may assist in diagnosing the
condition.

1F – 468IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0401
EXHAUST GAS RECIRCULATION INSUFFICIENT FLOW
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Nitrogen Oxide (NOx) emission levels caused by
high combustion temperatures. It accomplishes this by
feeding small amounts of exhaust gases back into the
combustion chamber. When the air/fuel mixture is diluted
with the exhaust gases, combustion temperatures are re-
duced
A linear EGR valve is used on this system. The linear EGR
valve is designed to accurately supply exhaust gases to
the engine without the use of intake manifold vacuum. The
valve controls exhaust flow going into the intake manifold
from the exhaust manifold through an orifice with an En-
gine Control Module (ECM) controlled pintle. The ECM
controls the pintle position using inputs from the Throttle
Position (TP) and Manifold Absolute Pressure (MAP) sen-
sors. The ECM then commands the EGR valve to operate
when necessary by controlling an ignition signal through
the ECM. This can be monitored on a scan tool as the De-
sired EGR Position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EGR valve, a voltage signal representing the
EGR valve pintle position is sent to the ECM. This feed-
back signal can also be monitored on a scan tool and is the
actual position of the EGR pintle. The Actual EGR Position
should always be near the commanded or Desired EGR
Position.
This diagnostic will determine if there is a reduction in EGR
flow.
Conditions for Setting the DTC
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0201, P0202, P0203, P0204,
P0351, P0352, P0402, P0404, P1404, P0405,
P0406 and P0502 are not set.
S Test in Decel Fuel Cutoff (DFCO) mode.
S Barometric Pressure (BARO) is greater than 72
kPa (10.4 psi).
S Vehicle speed is greater than 18 km/h (11.2
mph).
S A/C clutch/transmission clutch are unchanged.
S Rpm is between 1400 and 3000 for manual
transaxle.
S Rpm is between 1300 and 2900 for automatic
transaxle.
S Compensated MAP is with 10.3 to 32 kpa (1.5 to
4.6 psi) range.
S Start test
S Throttle position (TP) sensor is less then 1%.
S EGR is less than 1%.
S Change in MAP is less than 1.0 kpa (0.15 psi)Note : Test will be aborted when:
S Change in vehicle speed is greater than 5km/h (3.1
mph).
S Rpm is increased more than 75.
S EGR opened less than 90% commanded position.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will not illumi-
nate.
S The ECM will store conditions which were present
when the DTC set as Failure Records data only.
This information will not be stored in the Freeze
Frame data.
S A history Diagnostic Trouble Code (DTC) is stored.
S EGR is disabled.
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
The EGR Decel Filter value can be a great aid in determin-
ing if a problem exists and to verify repairs. The EGR De-
cel Filter is an average of the difference in the expected
MAP change and the actual MAP change caused by open-
ing the EGR valve during a deceleration, and is used to de-
termine when the MIL is illuminated. By driving the vehicle
up to approximately 97 km/h (60 mph) and decelerating to
32 km/h (20 mph), it can be determined if the EGR system
is OK, partially restricted, or fully restricted.
A more negative number (less than –3) indicates that the
system is working normally, whereas a positive number in-
dicates that the system is being restricted and that the ex-
pected amount of EGR flow is was not seen. A number
that falls between negative 3 and positive 2 indicates that
the system is partially restricted but not restricted enough
to cause an emissions impact.
The EGR Decel Filter value should always be at –3 or low-
er. If the EGR Decel Filter number becomes more positive
(towards 0 or more), then the EGR system is becoming re-
stricted. Look for possible damage to the EGR pipe or for
a restriction caused by carbon deposits in the EGR pas-
sages or on the EGR valve.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic Table.
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

1F – 470IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0402
EXHAUST GAS RECIRCULATION EXCESSIVE FLOW
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Nitrogen Oxide (NOx) emission levels caused by
high combustion temperatures. It accomplishes this by
feeding small amounts of exhaust gases back into the
combustion chamber. When the air/fuel mixture is diluted
with the exhaust gases, combustion temperatures are re-
duced
A linear EGR valve is used on this system. The linear EGR
valve is designed to accurately supply exhaust gases to
the engine without the use of intake manifold vacuum. The
valve controls exhaust flow going into the intake manifold
from the exhaust manifold through an orifice with an En-
gine Control Module (ECM) controlled pintle. The ECM
controls the pintle position using inputs from the Throttle
Position (TP) and Manifold Absolute Pressure (MAP) sen-
sors. The ECM then commands the EGR valve to operate
when necessary by controlling an ignition signal through
the ECM. This can be monitored on a scan tool as the De-
sired EGR Position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EGR valve, a voltage signal representing the
EGR valve pintle position is sent to the ECM. This feed-
back signal can also be monitored on a scan tool and is the
actual position of the EGR pintle. The Actual EGR Position
should always be near the commanded or Desired EGR
Position.
This Diagnostic Trouble Code (DTC) will detect an EGR
open to a large valve during crank. Crank time may be ex-
cessive with an open EGR valve.Conditions for Setting the DTC
S EGR position is greater than 70% for more than 3
seconds during cranking.
S Engine cranking (not running).
S Ignition voltage is between 10 and 16 volts.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive 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 Diagnostic Trouble Code (DTC) is stored.
S EGR is disabled.
Conditions for Clearing the MIL/DTC
S The MIL will turns 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
Due to moisture associated with exhaust systems, the
EGR valve may freeze and stick in cold weather at times.
After the vehicle is brought into a warm shop for repairs,
the valve warms and the problem disappears. By watching
the Actual EGR and Desired EGR Positions on a cold ve-
hicle with a scan tool, the fault can be easily verified.
Check the freeze frame data to determine if the DTC set
when the vehicle was cold by viewing the Engine Coolant
Temperature (ECT).

1F – 474IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0404
EXHAUST GAS RECIRCULATION OPEN VALVE POSITION
ERROR
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Nitrogen Oxide (NOx) emission levels caused by
high combustion temperatures. It accomplishes this by
feeding small amounts of exhaust gases back into the
combustion chamber. When the air/fuel mixture is diluted
with the exhaust gases, combustion temperatures are re-
duced
A linear EGR valve is used on this system. The linear EGR
valve is designed to accurately supply exhaust gases to
the engine without the use of intake manifold vacuum. The
valve controls exhaust flow going into the intake manifold
from the exhaust manifold through an orifice with an En-
gine Control Module (ECM) controlled pintle. The ECM
controls the pintle position using inputs from the Throttle
Position (TP) and Manifold Absolute Pressure (MAP) sen-
sors. The ECM then commands the EGR valve to operate
when necessary by controlling an ignition signal through
the ECM. This can be monitored on a scan tool as the De-
sired EGR Position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EGR valve, a voltage signal representing the
EGR valve pintle position is sent to the ECM. This feed-
back signal can also be monitored on a scan tool and is the
actual position of the EGR pintle. The Actual EGR Position
should always be near the commanded or Desired EGR
Position.
This Diagnostic Trouble Code (DTC) will detect an open
valve position.
Conditions for Setting the DTCS Difference between current and commended posi-
tion is greater than 15%.
S Desired EGR position is greater than 0.
S Change in Desired EGR is less than 3%.
S Engine is running.
S Ignition voltage is between 11.7 and 16 volts.
S Air temperature is greater than 3°C.
S DTCs P0112, P0113 P0405, P0406, and P0502 are
not set.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illumi-
nate, after three concecutive 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 Diagnostic Trouble Code (DTC) is stored.
S EGR is disabled.
Conditions for Clearing the MIL/DTC
S The MIL will turns 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
Due to moisture associated with exhaust systems, the
EGR valve may freeze and stick in cold weather at times.
After the vehicle is brought into a warm shop for repairs,
the valve warms and the problem disappears. By watching

1F – 478IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0405
EXHAUST GAS RECIRCULATION PINTLE POSITION LOW
VOLTAGE
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Nitrogen Oxide (NOx) emission levels caused by
high combustion temperatures. It accomplishes this by
feeding small amounts of exhaust gases back into the
combustion chamber. When the air/fuel mixture is diluted
with the exhaust gases, combustion temperatures are re-
duced
A linear EGR valve is used on this system. The linear EGR
valve is designed to accurately supply exhaust gases to
the engine without the use of intake manifold vacuum. The
valve controls exhaust flow going into the intake manifold
from the exhaust manifold through an orifice with an En-
gine Control Module (ECM) controlled pintle. The ECM
controls the pintle position using inputs from the Throttle
Position (TP) and Manifold Absolute Pressure (MAP) sen-
sors. The ECM then commands the EGR valve to operate
when necessary by controlling an ignition signal through
the ECM. This can be monitored on a scan tool as the De-
sired EGR Position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EGR valve, a voltage signal representing the
EGR valve pintle position is sent to the ECM. This feed-
back signal can also be monitored on a scan tool and is the
actual position of the EGR pintle. The Actual EGR Position
should always be near the commanded or Desired EGR
Position. This diagnostic Trouble Code (DTC) will detect
an open or short circuit.Conditions for Setting the DTC
S EGR position signal is less than 2%.
S Ignition voltage is between 11.7 and 16 volts.
S Fail condition last more than 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 Diagnostic Trouble Code (DTC) is stored.
S EGR is disabled.
Conditions for Clearing the MIL/DTC
S The MIL will turns 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
Due to moisture associated with exhaust systems, the
EGR valve may freeze and stick in cold weather at times.
After the vehicle is brought into a warm shop for repairs,
the valve warms and the problem disappears. By watching
the Actual EGR and Desired EGR Positions on a cold ve-
hicle with a scan tool, the fault can be easily verified.
Check the freeze frame data to determine if the DTC set
when the vehicle was cold by viewing the Engine Coolant
Temperature (ECT).

ENGINE CONTROLS 1F – 481
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0406
EXHAUST GAS RECIRCULATION PINTLE POSITION HIGH
VOLTAGE
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Nitrogen Oxide (NOx) emission levels caused by
high combustion temperatures. It accomplishes this by
feeding small amounts of exhaust gases back into the
combustion chamber. When the air/fuel mixture is diluted
with the exhaust gases, combustion temperatures are re-
duced
A linear EGR valve is used on this system. The linear EGR
valve is designed to accurately supply exhaust gases to
the engine without the use of intake manifold vacuum. The
valve controls exhaust flow going into the intake manifold
from the exhaust manifold through an orifice with an En-
gine Control Module (ECM) controlled pintle. The ECM
controls the pintle position using inputs from the Throttle
Position (TP) and Manifold Absolute Pressure (MAP) sen-
sors. The ECM then commands the EGR valve to operate
when necessary by controlling an ignition signal through
the ECM. This can be monitored on a scan tool as the De-
sired EGR Position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EGR valve, a voltage signal representing the
EGR valve pintle position is sent to the ECM. This feed-
back signal can also be monitored on a scan tool and is the
actual position of the EGR pintle. The Actual EGR Position
should always be near the commanded or Desired EGR
Position. This diagnostic Trouble Code (DTC) will detect
short circuit.Conditions for Setting the DTC
S EGR position signal is greater than 98%.
S Ignition voltage is between 11.7 and 16 volts.
S Fail condition last more than 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 Diagnostic Trouble Code (DTC) is stored.
S EGR is disabled.
Conditions for Clearing the MIL/DTC
S The MIL will turns 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
Due to moisture associated with exhaust systems, the
EGR valve may freeze and stick in cold weather at times.
After the vehicle is brought into a warm shop for repairs,
the valve warms and the problem disappears. By watching
the Actual EGR and Desired EGR Positions on a cold ve-
hicle with a scan tool, the fault can be easily verified.
Check the freeze frame data to determine if the DTC set
when the vehicle was cold by viewing the Engine Coolant
Temperature (ECT).

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