2004 DAEWOO LACETTI service

ENGINE CONTROLS 1F – 235
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0445
EVAP PURGE CONTROL CIRCUIT FAULT
Circuit Description
The evaporative emission (EVAP) system includes the fol-
lowing components :
S Fuel tank.
S EVAP vent solenoid.
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 canister purge valve.
S EVAP service port.
The evaporative emission system is checked by applying
vacuum to the EVAP system and monitoring for a vacuum
decay. The engine control module(ECM) monitors the
vacuum level through the fuel tank pressure sensor signal.
At the appropriate time, the EVAP canister purge valve
and the EVAP vent solenoid are turned on, allowing the en-
gine to draw a small vacuum on the entire EVAP system.
After the desired vacuum level has been achieved, the
EVAP canister purge valve is turned OFF, sealing the sys-tem. If a sufficient vacuum level cannot be achieved, a
large leak is indicated. This can be caused by the following
conditions :
Missing or faulty fuel cap.
Disconnected or faulty fuel tank pressure sensor.
Disconnected, damaged, pinched, or blocked EVAP
purge line.
Disconnected or faulty EVAP canister purge valve.
Disconnected or faulty EVAP vent solenoid.
Open ignition feed circuit to the EVAP vent or purge sole-
noid.
Damaged EVAP canister.
Leaking fuel sensor assembly O–ring.
Leaking fuel tank or fuel filler beck.
Any of the above conditions can set DTC P0445.
The test is failed if the tank vacuum is less than 10 in H20
for 15 seconds and the manifold vacuum integral is greater
than 49512 (proportional to purge mass from the tank).
Conditions for Setting the DTC
S The canister purge solenoid valve circuit is a short
to battery or short to ground condition exist.

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.

ENGINE CONTROLS 1F – 499
DAEWOO V–121 BL4
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
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.
VSS signal circuit 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
S Physical damage to the wiring harness
Ensure the VSS is correctly tightened with proper torque
to the transmission housing.
Refer to ”Intermittents”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.
2. The permanent magnet generator only produces a
signal if the drive wheels are turning greater than 5
mph (8 km/h). This step determines if DTC P0502
is the result of a hard failure or an intermittent con-
dition.
3. Proper engine loads cannot be achieved in a shop
environment to properly run the vehicle within the
Freeze Frame Data conditions. It will be necessary
to drive the vehicle on the road to obtain the proper
engine loads.
4. This step verifies that the ECM is receiving a signal
from the vehicle speed sensor.
5. Refer to service bulletin information for the latest
calibration update.
6. Refer to the latest Techline information for program-
ming procedures.
8. A resistance reading that is higher than the speci-
fied value indicates that the VSS circuitry is open.
10. If the displayed resistance is less than the 1300
ohms, the VSS high and low circuits are shorted
together.
11. This checks the resistance of the VSS if no opens
or shorts were found on the VSS high and low cir-
cuits.
13. The replacement ECM must be reprogrammed.
Refer to the latest Techline procedure for ECM re-
programming.
DTC P0502 – Vehicle Speed Sensor No Signal (Engine Side)
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”
2Notice : Running the vehicle in gear with the wheels
hanging down at full travel will damage the drive
axles.
1. Install a scan tool to the Data Link Connector
(DLC).
2. Raise the drive wheels.
3. Support the lower control arms so that the
drive axles are in a horizontal (straight) posi-
tion.
4. Start the engine and allow to idle in gear.
Does the scan tool display vehicle speed above the
specific value?0 mphGo to Step 3Go to Step 4

1F – 576IENGINE CONTROLS
DAEWOO V–121 BL4
HARD START
Definition : The engine cranks OK, but does not start for
a long time. The engine eventually runs or may start and
immediately die.Important : Ensure that the driver is using the correct
starting procedure. Before diagnosing, check service bul-
letins for updates.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. Connect the scan tool to the Data Link Con-
nector (DLC).
2. Check the Engine Coolant Temperature (ECT)
sensor and the Intake Air Temperature (IAT)
sensor using the scan tool.
3. Compare the coolant temperature and the IAT
with the ambient temperature when the engine
is cold.
Do the ECT and the IAT readings differ from the am-
bient temperature by more than the value specified?5°F (3°C)Go toStep 3Go toStep 4
31. Measure the resistance of the ECT and the IAT
sensor.
2. Compare the resistance value to specifications
using the Temperature Vs. Resistance tables
for diagnostic trouble codes (DTCs) P0118 and
P0113.
3. If the resistance is not the same, replace the
faulty sensor.
Is the repair complete?–System OK–
41. Check for a sticking throttle shaft or a binding
linkage that may cause a high Throttle Position
(TP) sensor voltage. Repair or replace as
needed.
2. Check the TP sensor voltage reading with the
throttle closed.
Does the voltage measure within the value speci-
fied?0.4–0.8 vGo toStep 5Go toStep 26
51. Check the Manifold Absolute Pressure (MAP)
sensor response and accuracy.
2. Replace the MAP sensor as needed.
Is the repair complete?–System OKGo toStep 6
6Check the fuel pump operation.
Does the fuel pump operate for the specified time
when the ignition switch is turned ON?2 secGo toStep 7Go to
”Fuel Pump
Relay Circuit
Check”
7Check the fuel system pressure.
Is the fuel pressure within the specifications?41–47 psi
(284–325 kPa)Go toStep 8Go toStep 29
8Check for water contamination in the fuel.
Is fuel contaminated?–Go toStep 9Go toStep 10
9Replace the contaminated fuel.
Is the repair complete?–System OK–

ENGINE CONTROLS 1F – 579
DAEWOO V–121 BL4
SURGES OR CHUGGLES
Definition : Engine power varies under steady throttle or
cruise, making it feel as if the vehicle speeds up and slows
down with no change in the accelerator pedal position.
Important : Make sure the driver understands Torque
Converter Clutch (TCC) and A/C compressor operation as
described in the owner’s manualThe speedometer reading and the speed reading on the
scan tool should be equal.
Before diagnosing the symptom, check service bulletins
for updates.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
2Connect the scan tool to the Data Link Connector
(DLC).
Does the Front Heated Oxygen Sensor (HO2S1) re-
spond quickly to different throttle positions?–Go toStep 4Go toStep 3
31. Check the HO2S1 sensor for silicone or other
contaminants from fuel or use of improper
Room Temperature Vulcanizing (RTV) sealant.
2. Replace the contaminated HO2S1 sensor.
Is the repair complete?–System OK–
41. Drive the vehicle at the speed of the complaint.
2. Monitor the long term fuel trim reading using
the scan tool.
Is the long term fuel trim reading within the value
specified?–20–25%Go toStep 7Go toStep 5
5Is the long term fuel trim reading below the value
specified?–20%Go to
”Diagnostic
Aids for DTC
P0172”Go toStep 6
6Is the long term fuel trim reading above the value
specified?25%Go to
”Diagnostic
Aids for DTC
P0171”–
7Check the fuel system pressure while the condition
exists.
Is the fuel system pressure within specifications?41–47 psi
(284–325 kPa)Go toStep 8Go toStep 17
8Check the in–line fuel filter.
Is the filter dirty or plugged?–Go toStep 18Go toStep 9
9Perform an injector diagnosis.
Does the injector balance test pinpoint the problem?–Go toStep 19Go toStep 10
101. Check for proper ignition voltage output using a
spark tester.
2. Inspect the spark plugs for cracks, wear, im-
proper gap, burned electrodes, or heavy de-
posits.
Is the problem found?–Go toStep 11Go toStep 12
11Repair or replace any ignition system components
as needed.
Is the repair complete?–System OK–

ENGINE CONTROLS 1F – 583
DAEWOO V–121 BL4
HESITATION, SAG, STUMBLE
Definition : Involves a momentary lack of response as the
accelerator is pushed down. This can occur at any vehicle
speed. It is usually the most severe when first trying to
make the vehicle move, as from a stop. Hesitation, sag,
or stumble may cause the engine to stall if severe enough.Important : Before diagnosing this condition, check ser-
vice bulletins for Programmable Read–Only Memory
(PROM) updates.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
21. Check the fuel system pressure. If the pres-
sure is not within the value specified, service
the fuel system as needed.
2. Inspect the Throttle Position (TP) sensor for
binding or sticking. The TP sensor voltage
should increase at a steady rate as the throttle
is moved toward Wide Open Throttle (WOT).
Is the problem found?41–47 psi
(284–325 kPa)Go toStep 3Go toStep 4
3Repair or replace any components as needed.
Is the repair complete?–System OK–
41. Check the Manifold Absolute Pressure (MAP)
sensor response and accuracy.
2. Inspect the fuel for water contamination.
3. Check the Evaporative (EVAP) Emission canis-
ter purge system for proper operation.
Is the problem found?–Go toStep 5Go toStep 6
5Repair or replace any components as needed.
Is the repair complete?–System OK–
61. Disconnect all of the fuel injector harness con-
nectors.
2. Connect an injector test light between the har-
ness terminals of each fuel injector.
3. Note the test light while cranking the engine.
Does the test light blink on all connectors?–Go toStep 8Go toStep 7
71. Repair or replace the faulty fuel injector drive
harness, the connector, or the connector termi-
nal.
2. If the connections and the harnesses are good,
replace the engine control module (ECM) for
an internal open in the fuel injector driver cir-
cuit.
Is the repair complete?–System OK–
8Measure the resistance of each fuel injector. The re-
sistance will increase slightly at higher tempera-
tures.
Is the fuel injector resistance within the value speci-
fied?11.6–12.4 ΩGo toStep 10Go toStep 9
9Replace any of the fuel injectors with a resistance
that is out of specifications.
Is the repair complete?–System OK–
10Perform an injector balance test.
Is the problem found?–Go toStep 11Go toStep 12

ENGINE CONTROLS 1F – 585
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
71. Perform a cylinder compression test.
2. If the compression is low, repair the engine as
needed.
3. Inspect for proper valve timing, bent pushrods,
worn rocker arms, broken or weak valve
springs, and worn camshaft lobes.
4. Inspect the intake manifold and the exhaust
manifold passages for casting flash.
Is the problem found?–Go toStep 8Go toStep 9
8Repair or replace any components as needed.
Is the repair complete?–System OK–
91. Check the fuel system for a plugged in–line fuel
filter.
2. Check the fuel system for low fuel pressure. If
the fuel pressure is below the value specified,
service the fuel system as needed.
3. Inspect for contaminated fuel.
Is the problem found?41–47 psi
(284–325 kPa)Go toStep 10Go toStep 11
10Repair or replace any components as needed.
Is the repair complete?–System OK–
111. Disconnect all of the fuel injector harness con-
nectors at the fuel injectors.
2. Connect an injector test light to the harness
terminals of each fuel injector connector.
3. Note the test light while cranking the engine for
each fuel injector.
Does the test light blink for all of the fuel injectors?–Go toStep 13Go toStep 12
121. Repair or replace the faulty injector drive circuit
harness, the connector, or the connector termi-
nal.
2. If the harness, the connectors, and the termi-
nals are OK, replace the engine control module
(ECM).
Is the repair complete?–System OK–
13Measure the resistance of each fuel injector. The re-
sistance will increase slightly at higher tempera-
tures.
Is the injector resistance within the value specified?11.6–12.4 ΩGo toStep 15Go toStep 14
14Replace any fuel injectors with a resistance that is
out of specifications.
Is the repair complete?–System OK–
15Perform an injector balance test.
Is the problem found?–Go toStep 16Go toStep 17
16Replace any restricted or leaking fuel injectors.
Is the repair complete?–System OK–

1F – 594IENGINE CONTROLS
DAEWOO V–121 BL4
MAINTENANCE AND REPAIR
ON–VEHICLE SERVICE
FUEL SYSTEM PRESSURE RELIEF
Procedure
CAUTION : The fuel system is under pressure. To
avoid fuel spillage and the risk of personal injury or
fire, it is necessary to relieve the fuel system pressure
before disconnecting the fuel lines.
1. Remove the fuel cap.
2. Remove the fuel pump fuse Ef18 from the engine
fuse block.
3. Start the engine and allow the engine to stall.
4. Crank the engine for an additional 10 seconds.
FUEL TANK
Removal Procedure
CAUTION : The fuel system is under pressure. To
avoid fuel spillage and the risk of personal injury or
fire, it is necessary to relieve the fuel system pressure
before disconnecting the fuel lines.
1. Relieve the fuel pressure. Refer to ” Fuel System
Pressure Relief ” in this section.
2. Disconnect the negative battery cable.
3. Drain the fuel tank.
4. Remove the front muffler. Refer to Section 1G, Ex-
haust System
5. Remove the fuel tank filler tube clamp at the fuel
tank.
6. Disconnect the fuel tank filler tube.
7. Disconnect the fuel vapor line near the fuel tank
filler tube.
8. Disconnect the fuel pump harness connector.