speed DAEWOO LACETTI 2004 Service Owners Manual

1F – 402IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
61. Disconnect the Manifold Absolute Pressure
(MAP) sensor electrical connector.
2. Operate the vehicle in Closed Loop while moni-
toring the Long Term Fuel Trim value.
Is the Long Term Fuel Trim value below the specified
value?25%Go to Step 15Go to Step 9
71. Repair the malfunction found in Step 5.
2. Recheck the Long Term Fuel Trim value while
operating the engine.
Is the Long Term Fuel Trim value below the specified
value?25%Go to Step 8Go to Step 9
8Lean condition is not present.
Does a driveability problem exist?–Go to
”Symptom
Diagnosis”Go to Step 16
91. Visually/physically inspect the following items
for vacuum leaks:
S Intake manifold.
S Throttle body.
S Injector O–rings.
2. Repair any leaks found as necessary.
Is the repair complete?–Go to Step 16Go to Step 10
10Allow the engine to idle.
Are the Idle Air Control (IAC) counts above the spe-
cified value?5Go to Step 11Go to Step 12
11Check the fuel for excessive water, alcohol, or other
contaminants and correct the contaminated fuel
condition if present.
Is the repair complete?–Go to Step 16Go to Step 13
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 16Go to Step 13
131. Connect a fuel pressure gauge to the fuel sys-
tem.
2. Turn the ignition OFF for at least 10 seconds.
3. Turn the ignition ON, with the engine OFF. The
fuel pump will run for approximately 2–3 sec-
onds. It may be necessary to cycle the ignition
switch ON more than once to obtain maximum
fuel pressure.
4. Note the fuel pressure with the fuel pump run-
ning. The pressure should be within the speci-
fied value. When the fuel pump stops, the pres-
sure may vary slightly then hold steady.
Is the fuel pressure steady and does the fuel pres-
sure hold?241–276 kPa
(35–40 psi)Go to Step 14Go to
”Fuel System
Diagnosis”

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–

1F – 408IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0201
INJECTOR 1 CIRCUIT FAULT
Circuit Description
The Engine Control Module (ECM) has four individual in-
jector driver circuits, each of which controls an injector.
When a driver circuit is grounded by the ECM, the injector
is activated. The ECM monitors the current in each driver
circuit. The ECM measures a voltage drop through a fixed
resistor and controls it. The voltage on each driver is moni-
tored to detect a fault. If the voltage is not what the ECM
expects to monitor on the circuit, a Diagnostic Trouble
Code (DTC) is set. This DTC detects a short to ground
and/or an open circuit and short to battery conditions for
low–side drive injector outputs.
Conditions for Setting the DTC
S Monitor fault feedback signal from FETS.
S Engine is in run mode.
S Battery voltage is greater than 9 volts.
S Engine speed is greater than 700 rpm.
S Fault is present for more than 5 seconds.
Action Taken When the DTC Sets
S The ECM will illuminate the Malfunction Indicator
Lamp (MIL) the first time the fault is Detected.S The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
S The ECM will turn off the MIL on the third consecu-
tive trip cycle in which the diagnostic has been run
and the fault is no longer present.
S A history will clear after 40 consecutive warm–up
cycles without a fault.
S DTC can be cleared by using the scan tool Clear
Info function.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
An injector 1 driver circuit that is open or shorted to voltage
will cause a DTC P0201 to set. It will also cause a misfire
due to an inoperative injector. A misfire DTC should also
be set indicating which injector is inoperative.
Long–term and short–term fuel trims that are excessively
high or low are a good indication that an injector is mal-
functioning. Refer to ”Fuel Injector Balance Test” in this
section to check for malfunctioning injectors.

ENGINE CONTROLS 1F – 411
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0202
INJECTOR 2 CIRCUIT FAULT
Circuit Description
The Engine Control Module (ECM) has four individual in-
jector driver circuits, each of which controls an injector.
When a driver circuit is grounded by the ECM, the injector
is activated. The ECM monitors the current in each driver
circuit. The ECM measures a voltage drop through a fixed
resistor and controls it. The voltage on each driver is moni-
tored to detect a fault. If the voltage is not what the ECM
expects to monitor on the circuit, a Diagnostic Trouble
Code (DTC) is set. This DTC detects a short to ground
and/or an open circuit and short to battery conditions for
low–side drive injector outputs.
Conditions for Setting the DTC
S Monitor fault feedback signal from FETS.
S Engine is in run mode.
S Battery voltage is greater than 9 volts.
S Engine speed is greater than 700 rpm.
S Fault is present for more than 5 seconds.
Action Taken When the DTC Sets
S The ECM will illuminate the Malfunction Indicator
Lamp (MIL) the first time the fault is Detected.S The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
S The ECM will turn off the MIL on the third consecu-
tive trip cycle in which the diagnostic has been run
and the fault is no longer present.
S A history will clear after 40 consecutive warm–up
cycles without a fault.
S DTC can be cleared by using the scan tool Clear
Info function.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
An injector 2 driver circuit that is open or shorted to voltage
will cause a DTC P0202 to set. It will also cause a misfire
due to an inoperative injector. A misfire DTC should also
be set indicating which injector is inoperative.
Long–term and short–term fuel trims that are excessively
high or low are a good indication that an injector is mal-
functioning. Refer to ”Fuel injector Balance Test” in this
section to check for malfunctioning injectors.

1F – 414IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0203
INJECTOR 3 CIRCUIT FAULT
Circuit Description
The Engine Control Module (ECM) has four individual in-
jector driver circuits, each of which controls an injector.
When a driver circuit is grounded by the ECM, the injector
is activated. The ECM monitors the current in each driver
circuit. The ECM measures a voltage drop through a fixed
resistor and controls it. The voltage on each driver is moni-
tored to detect a fault. If the voltage is not what the ECM
expects to monitor on the circuit, a Diagnostic Trouble
Code (DTC) is set. This DTC detects a short to ground
and/or an open circuit and short to battery conditions for
low–side drive injector outputs.
Conditions for Setting the DTC
S Monitor fault feedback signal from FETS.
S Engine is in run mode.
S Battery voltage is greater than 9 volts.
S Engine speed is greater than 700 rpm.
S Fault is present for more than 5 seconds.
Action Taken When the DTC Sets
S The ECM will illuminate the Malfunction Indicator
Lamp (MIL) the first time the fault is Detected.S The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
S The ECM will turn off the MIL on the third consecu-
tive trip cycle in which the diagnostic has been run
and the fault is no longer present.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC can be cleared by using the scan tool Clear
Info function.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
An injector 3 driver circuit that is open or shorted to voltage
will cause a DTC P0203 to set. It will also cause a misfire
due to an inoperative injector. A misfire DTC should also
be set indicating which injector is inoperative.
Long–term and short–term fuel trims that are excessively
high or low are a good indication that an injector is mal-
functioning. Refer to ”Fuel injector Balance Test” in this
section to check for malfunctioning injectors.

ENGINE CONTROLS 1F – 417
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0204
INJECTOR 4 CIRCUIT FAULT
Circuit Description
The Engine Control Module (ECM) has four individual in-
jector driver circuits, each of which controls an injector.
When a driver circuit is grounded by the ECM, the injector
is activated. The ECM monitors the current in each driver
circuit. The ECM measures a voltage drop through a fixed
resistor and controls it. The voltage on each driver is moni-
tored to detect a fault. If the voltage is not what the ECM
expects to monitor on the circuit, a Diagnostic Trouble
Code (DTC) is set. This DTC detects a short to ground
and/or an open circuit and short to battery conditions for
low–side drive injector outputs.
Conditions for Setting the DTC
S Monitor fault feedback signal from FETS.
S Engine is in run mode.
S Battery voltage is greater than 9 volts.
S Engine speed is greater than 700 rpm.
S Fault is present for more than 5 seconds.
Action Taken When the DTC Sets
S The ECM will illuminate the Malfunction Indicator
Lamp (MIL) the first time the fault is Detected.S The ECM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.
Conditions for Clearing the MIL/DTC
S The ECM will turn off the MIL on the third consecu-
tive trip cycle in which the diagnostic has been run
and the fault is no longer present.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC can be cleared by using the scan tool Clear
Info function.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
An injector 4 driver circuit that is open or shorted to voltage
will cause a DTC P0204 to set. It will also cause a misfire
due to an inoperative injector. A misfire DTC should also
be set indicating which injector is inoperative.
Long–term and short–term fuel trims that are excessively
high or low are a good indication that an injector is mal-
functioning. Refer to ”Fuel injector Balance Test” in this
section to check for malfunctioning injectors.

ENGINE CONTROLS 1F – 421
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0300
MULTIPLE CYLINDER MISFIRE DETECTED
System Description
The Engine Control Module (ECM) monitors the crank-
shaft and camshaft positions to detect if the engine is mis-
firing. The ECM looks for a quick drop in crankshaft speed.
This test is executed in blocks of 100 engine revolution
tests. It may take between one to several tests to store a
Diagnostic Trouble Code (DTC) and illuminate the Mal-
function Indicator Lamp (MIL). Under light misfire condi-
tions, it may also take more than one trip to set a DTC. Se-
vere misfire will flash the MIL, indicating that catalyst
damage is possible.
Conditions for Setting the DTC
S Emission threshold is 3%.
S 20 engine cycles have occurred since cranking has
started.
S A/C compressor clutch has not just engaged or dis-
engaged.
S Engine load and engine speed is in a detectable
region and is at or above zero torque.
S Camshaft Position (CMP) sensor is in synchroniza-
tion.
S Exhaust Gas Recirculation (EGR) flow diagnostic is
not in progress.
S Fuel level is greater than 12% of rated tank capac-
ity.
S Decel Fuel Cutoff (DFCO) not active.
S Throttle position change is less than 3% per 125
ms.
S Vehicle has not encountered an abusive engine
speed of 7000 rpm.
S Crankshaft speed patters are normal.
S Throttle position is less than 3% when vehicle
speed is greater than 10 km/h (6 mph).
S Vehicle voltage is between 11 and 16 volts.
S Engine Coolant Temperature (ECT) is between
–7°C (19°F) and 120°C (248°F).
S There is the correct ratio between Crankshaft Posi-
tion (CKP) sensor pulses and CMP sensor pulses.
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0336, P0337, P0341, P0342 and
P0502 are not set.
Action Taken When the DTC Sets
S The MIL will illuminate after two consecutive ignition
cycles in which the diagnostic runs with the fault
active.
Or
S The MIL will illuminate immediately and flash if mis-
fire is present.
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
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
An intermittent can also be the result of a defective reluctor
wheel. Remove the CKP sensor and inspect the reluctor
wheel through the sensor mount hole. Check for porosity
and the condition of wheel. If the DTC is intermittent refer
to ”Symptoms Diagnosis” in this section.
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.
3. A visual/physical inspection should include check-
ing the following components:
S The wiring for proper connections, pinches or
cuts.
S The ECM grounds for being clean and tight.
S The vacuum hoses for splits, kinks, and proper
connections as shown on the Vehicle Emission
Information label. Check thoroughly for any type
of leak or restriction.
S For air leaks at the throttle body mounting area
and intake manifold sealing surfaces.
5. When all the accumulators are relatively equal, then
the misfire is being caused by something that af-
fects the entire engine. When they are not then the
misfire is being caused by something that is specif-
ic to two or more cylinders.
6. Whenever the misfire is not present operating the
vehicle may be necessary to duplicate the condi-
tions in the Freeze Frame Data in order to detect
misfire. Depending on the engine load, the condi-
tions may have to be maintained for up to 20 sec-
onds. Whenever the misfire accumulators start to
increment, then misfire is present. A history misfire
counter will store the number of misfires that have
occurred until the DTC is cleared.

1F – 426IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0301
CYLINDER 1 MISFURE
System Description
The Engine Control Module (ECM) monitors the crank-
shaft and camshaft positions to detect if the engine is mis-
firing. The ECM looks for a quick drop in crankshaft speed.
This test is executed in blocks of 100 engine revolution
tests. It may take between one to several tests to store a
Diagnostic Trouble Code (DTC) and illuminate the Mal-
function Indicator Lamp (MIL). Under light misfire condi-
tions, it may also take more than one trip to set a DTC. Se-
vere misfire will flash the MIL, indicating that catalyst
damage is possible.
Conditions for Setting the DTC
S Emission threshold is 3%.
S 20 engine cycles have occurred since cranking has
started.
S A/C compressor clutch has not just engaged or dis-
engaged.
S Engine load and engine speed is in a detectable
region and is at or above zero torque.
S Camshaft Position (CMP) sensor is in synchroniza-
tion.
S Exhaust Gas Recirculation (EGR) flow diagnostic is
not in progress.
S Fuel level is greater than 12% of rated tank capac-
ity.
S Decel Fuel Cutoff (DFCO) not active.
S Throttle position change is less than 3% per 125
ms.
S Vehicle has not encountered an abusive engine
speed of 7000 rpm.
S Crankshaft speed patters are normal.
S Throttle position is less than 3% when vehicle
speed is greater than 10 km/h (6 mph).
S Vehicle voltage is between 11 and 16 volts.
S Engine Coolant Temperature (ECT) is between
–7°C (19°F) and 120°C (248°F).
S There is the correct ratio between Crankshaft Posi-
tion (CKP) sensor pulses and CMP sensor pulses.
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0336, P0337, P0341, P0342 and
P0502 are not set.
Action Taken When the DTC Sets
S The MIL will illuminate after two consecutive ignition
cycles in which the diagnostic runs with the fault
active.
Or
S The MIL will illuminate immediately and flash if mis-
fire is present.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
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
An intermittent can also be the result of a defective reluctor
wheel. Remove the CKP sensor and inspect the reluctor
wheel through the sensor mount hole. Check for porosity
and the condition of wheel. If the DTC is intermittent refer
to ”Symptoms Diagnosis” in this section.
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.
3. A visual/physical inspection should include check-
ing the following components:
S The wiring for proper connections, pinches or
cuts.
S The ECM grounds for being clean and tight.
S The vacuum hoses for splits, kinks, and proper
connections as shown on the Vehicle Emission
Information label.
S Check thoroughly for any type of leak or restric-
tion.
S For air leaks at the throttle body mounting area
and intake manifold sealing surfaces.
5. When all the accumulators are relatively equal, then
the misfire is being caused by something that af-
fects the entire engine. When they are not then the
misfire is being caused by something that is specif-
ic to two or more cylinders.
6. Whenever the misfire is not present operating the
vehicle may be necessary to duplicate the condi-
tions in the Freeze Frame Data in order to detect

ENGINE CONTROLS 1F – 431
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0302
CYLINDER 2 MISFIRE
System Description
The Engine Control Module (ECM) monitors the crank-
shaft and camshaft positions to detect if the engine is mis-
firing. The ECM looks for a quick drop in crankshaft speed.
This test is executed in blocks of 100 engine revolution
tests. It may take between one to several tests to store a
Diagnostic Trouble Code (DTC) and illuminate the Mal-
function Indicator Lamp (MIL). Under light misfire condi-
tions, it may also take more than one trip to set a DTC. Se-
vere misfire will flash the MIL, indicating that catalyst
damage is possible.
Conditions for Setting the DTC
S Emission threshold is 3%.
S 20 engine cycles have occurred since cranking has
started.
S A/C compressor clutch has not just engaged or dis-
engaged.
S Engine load and engine speed is in a detectable
region and is at or above zero torque.
S Camshaft Position (CMP) sensor is in synchroniza-
tion.
S Exhaust Gas Recirculation (EGR) flow diagnostic is
not in progress.
S Fuel level is greater than 12% of rated tank capac-
ity.
S Decel Fuel Cutoff (DFCO) not active.
S Throttle position change is less than 3% per 125
ms.
S Vehicle has not encountered an abusive engine
speed of 7000 rpm.
S Crankshaft speed patters are normal.
S Throttle position is less than 3% when vehicle
speed is greater than 10 km/h (6 mph).
S Vehicle voltage is between 11 and 16 volts.
S Engine Coolant Temperature (ECT) is between
–7°C (19°F) and 120°C (248°F).
S There is the correct ratio between Crankshaft Posi-
tion (CKP) sensor pulses and CMP sensor pulses.
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0336, P0337, P0341, P0342 and
P0502 are not set.
Action Taken When the DTC Sets
S The MIL will illuminate after two consecutive ignition
cycles in which the diagnostic runs with the fault
active.
Or
S The MIL will illuminate immediately and flash if mis-
fire is present.
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
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
An intermittent can also be the result of a defective reluctor
wheel. Remove the CKP sensor and inspect the reluctor
wheel through the sensor mount hole. Check for porosity
and the condition of wheel. If the DTC is intermittent refer
to”Symptoms Diagnosis” in this section.
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.
3. A visual/physical inspection should include check-
ing the following components:
S The wiring for proper connections, pinches or
cuts.
S The ECM grounds for being clean and tight.
S The vacuum hoses for splits, kinks, and proper
connections as shown on the Vehicle Emission
Information label. Check thoroughly for any type
of leak or restriction.
S For air leaks at the throttle body mounting area
and intake manifold sealing surfaces.
5. When all the accumulators are relatively equal, then
the misfire is being caused by something that af-
fects the entire engine. When they are not then the
misfire is being caused by something that is specif-
ic to two or more cylinders.
6. Whenever the misfire is not present operating the
vehicle may be necessary to duplicate the condi-
tions in the Freeze Frame Data in order to detect
misfire. Depending on the engine load, the condi-
tions may have to be maintained for up to 20 sec-
onds. Whenever the misfire accumulators start to
increment, then misfire is present. A history misfire
counter will store the number of misfires that have
occurred until the DTC is cleared.