tank DAEWOO LACETTI 2004 Service Owner's Manual

ENGINE CONTROLS 1F – 5
DAEWOO V–121 BL4
SYMPTOM DIAGNOSIS1F–574 . . . . . . . . . . . . . . . . . . .
Important Preliminary Checks 1F–574. . . . . . . . . . . . .
Intermittents 1F–574. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hard Start 1F–576. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Surges or Chuggles 1F–579. . . . . . . . . . . . . . . . . . . . . .
Lack of Power, Sluggishness, or Sponginess 1F–581
Hesitation, Sag, Stumble 1F–583. . . . . . . . . . . . . . . . .
Cuts Out, Misses 1F–584. . . . . . . . . . . . . . . . . . . . . . . .
Poor Fuel Economy 1F–587. . . . . . . . . . . . . . . . . . . . . .
Rough, Unstable, or Incorrect Idle, Stalling 1F–588. .
Excessive Exhaust Emissions or Odors 1F–591. . . . .
Dieseling, Run–On 1F–592. . . . . . . . . . . . . . . . . . . . . . .
Backfire 1F–593. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MAINTENANCE AND REPAIR1F–594 . . . . . . . . . . . . .
ON–VEHICLE SERVICE 1F–594. . . . . . . . . . . . . . . . . . .
Fuel System Pressure Relief 1F–594. . . . . . . . . . . . . .
Fuel Tank 1F–594. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Pump 1F–596. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Filter 1F–597. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Rail and Injectors (1.4L/1.6L DOHC) 1F–598. . .
Fuel Rail and Injectors (1.8L DOHC) 1F–600. . . . . . .
Engine Coolant Temperature Sensor
(1.4L/1.6L DOHC) 1F–602. . . . . . . . . . . . . . . . . . . . . .
Engine Coolant Temperature Sensor
(1.8L DOHC) 1F–602. . . . . . . . . . . . . . . . . . . . . . . . . .
Throttle Position Sensor (1.8L DOHC) 1F–603. . . . . .
Throttle Body (1.4L/1.6L DOHC) 1F–603. . . . . . . . . . .
Throttle Body (1.8L DOHC) 1F–604. . . . . . . . . . . . . . .
Front Heated Oxygen Sensor (HO2S 1)
(1.4L/1.6L DOHC) 1F–606. . . . . . . . . . . . . . . . . . . . . .
Front Heated Oxygen Sensor (HO2S 1)
(1.8L DOHC) 1F–607. . . . . . . . . . . . . . . . . . . . . . . . . .
Rear Heated Oxygen Sensor (HO2S 2) 1F–607. . . . .
Intake Air Temperature Sensor
(1.4L/1.6L DOHC) 1F–608. . . . . . . . . . . . . . . . . . . . . .
Intake Air Temperature Sensor (1.8L DOHC) 1F–609
Idle Air Control Valve (1.8L DOHC) 1F–609. . . . . . . . .
Manifold Absolute Pressure Sensor
(1.4L/1.6L DOHC) 1F–610. . . . . . . . . . . . . . . . . . . . . .
Manifold Absolute Pressure Sensor
(1.8L DOHC) 1F–611. . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust Gas Recirculation Valve
(1.4L/1.6L DOHC) 1F–611. . . . . . . . . . . . . . . . . . . . . .
Exhaust Gas Recirculation Valve (1.8L DOHC) 1F–612
Knock Sensor (1.4L/1.6L DOHC) 1F–612. . . . . . . . . .
Knock Sensor (1.8L DOHC) 1F–613. . . . . . . . . . . . . . .
Evaporative Emission Canister 1F–614. . . . . . . . . . . . Evaporative Emission Canister Purge Solenoid Valve 1
F–615
Crankshaft Position (CKP) Sensor
(1.4L/1.6L DOHC) 1F–615. . . . . . . . . . . . . . . . . . . . . .
Crankshaft Position (CKP) Sensor
(1.8L DOHC) 1F–616. . . . . . . . . . . . . . . . . . . . . . . . . .
Camshaft Position Sensor (1.4L/1.6L DOHC) 1F–618
Camshaft Position Sensor (1.8L DOHC) 1F–619. . . .
Engine Control Module (1.4L/1.6L DOHC) 1F–620. . .
Engine Control Module (1.8L DOHC) 1F–621. . . . . . .
Electronic Ignition System Ignition Coil
(1.4L/1.6L DOHC) 1F–621. . . . . . . . . . . . . . . . . . . . . .
Electronic Ignition System Ignition Coil
(1.8L DOHC) 1F–622. . . . . . . . . . . . . . . . . . . . . . . . . .
GENERAL DESCRIPTION AND SYSTEM
OPERATION1F–623 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition System Operation 1F–623. . . . . . . . . . . . . . . .
Electronic Ignition System Ignition Coil 1F–623. . . . . .
Crankshaft Position Sensor 1F–623. . . . . . . . . . . . . . .
Camshaft Position Sensor 1F–623. . . . . . . . . . . . . . . .
Idle Air System Operation 1F–623. . . . . . . . . . . . . . . . .
Fuel Control System Operation 1F–623. . . . . . . . . . . .
Evaporative Emission Control System
Operation 1F–624. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Evaporative Emission Canister 1F–625. . . . . . . . . . . .
Positive Crankcase Ventilation System
Operation 1F–625. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Coolant Temperature Sensor 1F–625. . . . . . .
Throttle Position Sensor 1F–625. . . . . . . . . . . . . . . . . .
Catalyst Monitor Oxygen Sensors 1F–625. . . . . . . . . .
Exhaust Gas Recirculation Valve 1F–626. . . . . . . . . . .
Intake Air Temperature Sensor 1F–626. . . . . . . . . . . .
Idle Air Control Valve 1F–626. . . . . . . . . . . . . . . . . . . . .
Manifold Absolute Pressure Sensor 1F–626. . . . . . . .
Engine Control Module 1F–627. . . . . . . . . . . . . . . . . . .
Fuel Injector 1F–627. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Knock Sensor 1F–627. . . . . . . . . . . . . . . . . . . . . . . . . . .
Rough Road Sensor 1F–627. . . . . . . . . . . . . . . . . . . . .
Strategy–Based Diagnostics 1F–628. . . . . . . . . . . . . .
EOBD Serviceability Issues 1F–628. . . . . . . . . . . . . . .
Serial Data Communications 1F–629. . . . . . . . . . . . . .
On–Board Diagnostic (EOBD) 1F–629. . . . . . . . . . . . .
Comprehensive Component Monitor Diagnostic
Operation 1F–630. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Common EOBD Terms 1F–630. . . . . . . . . . . . . . . . . . .
Reading Diagnostic Trouble Codes 1F–632. . . . . . . . .
Primary System–Based Diagnostics 1F–633. . . . . . . .

1F – 8IENGINE CONTROLS
DAEWOO V–121 BL4
EGR Desired Position
The desired exhaust gas recirculation (EGR) position is
the commanded EGR position. The ECM calculates the
desired EGR position. The higher the percentage, the lon-
ger the ECM is commanding the EGR valve ON.
Engine Load
Indicates engine load based on manifold absolute pres-
sure. The higher the percentage, the more load the engine
is under.
Engine Run Time
The engine run time is a measure of how long the engine
has been running. When the engine stops running, the tim-
er resets to zero.
Engine Speed
Engine Speed is computed by the ECM from the fuel con-
trol reference input. It should remain close to desired idle
under the various engine loads with the engine idling.
Fan
The Fan Control (FC) Relay is commanded by the ECM.
The FC Relay displays the command as ON or OFF.
Fuel Level Sensor
The Fuel Level Sensor monitors the fuel level in the tank.
The Fuel Level Sensor monitors the rate of change of the
air pressure in the EVAP system. Several of the Enhanced
EVAP System diagnostics are dependent upon the correct
fuel level.
Fuel System Status
The Closed Loop is displayed indicating that the ECM is
controlling the fuel delivery according to the Front Heated
Oxygen Sensor (HO2S1) voltage as close to an air/fuel ra-
tio of 14.7 to 1 as possible.
IAC Position
The scan tool displays the ECM command for the Idle Air
Control (IAC) pintle position in counts. The higher the
number of counts, the greater the commanded idle speed
reads. The Idle Air Control responds to changes in the en-
gine load in order to maintain the desired idle rpm.
Ignition 1 (Voltage)
The ignition volts represent the system voltage measured
by the ECM at the ignition feed circuit.
Intake Air Temperature
The ECM converts the resistance of the Intake Air Tem-
perature (IAT) sensor to degrees in the same manner as
the engine coolant temperature (ECT) sensor. In take air
temperature is used by the ECM to adjust fuel delivery and
spark timing according to incoming air density.Knock Present
The KS Noise Channel indicates when the ECM detects
the KS signal. The ECM should display NO at idle.
Long Term FT
The Long Term Fuel Trim (FT) is derived from the short
term fuel trim value. The Long Term FT is used for the long
term correction of the fuel delivery. A value of 128 counts
(0%) indicates that the fuel delivery requires no com-
pensation in order to maintain a 14.7:1 air to fuel ratio. A
value below 128 counts means that the fuel system is too
rich and the fuel delivery is being reduced. The ECM is de-
creasing the injector pulse width. A value above 128
counts indicates that a lean condition exists for which the
ECM is compensating.
MAP
The Manifold Absolute Pressure (MAP) sensor measures
the change in the intake manifold pressure which results
from engine load and speed changes. As the intake man-
ifold pressure increases, the air density in the intake also
increases and the additional fuel is required.
Misfire History #1–4
Indicates the number of misfires that have occurred after
195 current misfires have been counted. The current mis-
fire counter will add its misfires to the history misfire count-
er after 195 total misfires have taken place. If 1 cylinder is
misfiring, the misfiring current counter will have 195 mis-
fires counted before adding to its history counter. If 2 cylin-
ders are misfiring, the misfiring current counter will add to
their history counters after 97 misfires. The counter incre-
ments only after a misfire diagnostic trouble code (DTC)
has been set.
Front Heated Oxygen Sensor
The pre–converter Front Heated Oxygen Sensor
(HO2S1) reading represents the exhaust oxygen sensor
output voltage. This voltage will fluctuate constantly be-
tween 100 mv (lean exhaust) and 900 mv (rich exhaust)
when the system is operating in a Closed Loop.
Rear Heated Oxygen Sensor
The post–converter Rear Heated Oxygen Sensor
(HO2S2) represents the exhaust oxygen output voltage
past the catalytic converter. This voltage remains inactive,
or the voltage will appear lazy within a range of 100 mv
(lean exhaust) and 900 mv (rich exhaust) when operating
in a Closed Loop.
Short Term FT
The Short Term FT represents a short term correction to
fuel delivery by the ECM in response to the amount of time
the oxygen sensor voltage spends above or below the 450
mv threshold. If the oxygen sensor has mainly been below
450 mv, indicating a lean air/fuel mixture, short term fuel
trim will increase to tell the ECM to add fuel. If the oxygen
sensor voltage stays mainly above the threshold, the ECM
will reduce fuel delivery to compensate for the indicated
rich condition.

1F – 10IENGINE CONTROLS
DAEWOO V–121 BL4
FASTENER TIGHTENING SPECIFICATIONS
ApplicationNSmLb–FtLb–In
Camshaft Position Sensor Bolts (1.4L/1.6L DOHC)7–62
Camshaft Position Sensor Bolts (1.8 DOHC)8–71
Crankshaft Position Sensor Retaining Bolt (1.4L/1.6L DOHC)6.5–58
Crankshaft Position Sensor Retaining Bolt (1.8 DOHC)8–71
Electronic Ignition System Ignition Coil Retaining Bolts10–89
Exhaust Gas Recirculation Valve Retaining Bolts3022–
Engine Control Module Bolts12–106
Engine Coolant Temperature Sensor Bolt (1.4L/1.6L DOHC)17.513–
Engine Coolant Temperature Sensor Bolt (1.8 DOHC)2015–
Evaporative Emission Canister Flange Bolt4–35
Evaporative Emission Canister Purge Solenoid Bracket Bolt5–44
Fuel Filter Mounting Bracket Assembly Bolt4–35
Fuel Tank Retaining Bolts2015–
Fuel Rail Retaining Bolts2518–
Idle Air Control Valve Retaining Bolts (1.8 DOHC)3–27
Intake Air Temperature Sensor2216–
Knock Sensor Bolt2015–
Manifold Absolute Pressure Sensor Bolts (1.4L/1.6L DOHC)8–71
Manifold Absolute Pressure Sensor Bolts (1.8 DOHC)4–35
Oxygen Sensor Bolt4231–
Throttle Body Retaining Nuts (1.4L/1.6L DOHC)1511–
Throttle Body Retaining Nuts (1.8 DOHC)10–89
Throttle Position Sensor Retaining Bolts (1.8 DOHC)2–18

1F – 30IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSIS
SYSTEM DIAGNOSIS
DIAGNOSTIC AIDS
If an intermittent problem is evident, follow the guidelines
below.
Preliminary Checks
Before using this section you should have already per-
formed the ”On–Board Diagnostic System Check.”
Perform a thorough visual inspection. This inspection can
often lead to correcting a problem without further checks
and can save valuable time. Inspect for the following con-
ditions:
S Engine control module (ECM) grounds for being
clean, tight, and in their proper location.
S Vacuum hoses for splits, kinks, collapsing and prop-
er connections as shown on the Vehicle Emission
Control Information label. Inspect thoroughly for
any type of leak or restriction.
S Air leaks at the throttle body mounting area and the
intake manifold sealing surfaces.
S Ignition wires for cracks, hardness, proper routing,
and carbon tracking.
S Wiring for proper connections.
S Wiring for pinches or cuts.
Diagnostic Trouble Code Tables
Do not use the Diagnostic Trouble Code (DTC) tables to
try to correct an intermittent fault. The fault must be pres-
ent to locate the problem.
Incorrect use of the DTC tables may result in the unneces-
sary replacement of parts.
Faulty Electrical Connections or Wiring
Most intermittent problems are caused by faulty electrical
connections or wiring. Perform a careful inspection of sus-
pect circuits for the following:
S Poor mating of the connector halves.
S Terminals not fully seated in the connector body.
S Improperly formed or damaged terminals. All con-
nector terminals in a problem circuit should be care-
fully inspected, reformed, or replaced to insure con-
tact tension.S Poor terminal–to–wire connection. This requires
removing the terminal from the connector body.
Road Test
If a visual inspection does not find the cause of the prob-
lem, the vehicle can be driven with a voltmeter or a scan
tool connected to a suspected circuit. An abnormal voltage
or scan tool reading will indicate that the problem is in that
circuit.
If there are no wiring or connector problems found and a
DTC was stored for a circuit having a sensor, except for
DTC P0171 and DTC P0172, replace the sensor.
Fuel System
Some intermittent driveability problems can be attributed
to poor fuel quality. If a vehicle is occasionally running
rough, stalling, or otherwise performing badly, ask the cus-
tomer about the following fuel buying habits:
S Do they always buy from the same source? If so,
fuel quality problems can usually be discounted.
S Do they buy their fuel from whichever fuel station
that is advertising the lowest price? If so, check the
fuel tank for signs of debris, water, or other contam-
ination.
IDLE LEARN PROCEDURE
Whenever the battery cables, the engine control module
(ECM), or the ECM fuse is disconnected or replaced, the
following idle learn procedure must be performed:
1. Turn the ignition ON for 5 seconds.
2. Turn the ignition OFF for 5 seconds.
3. Turn the ignition ON for 5 seconds.
4. Start the engine in park/neutral.
5. Allow the engine to run until the engine coolant is
above 185° F (85°C ).
6. Turn the A/C ON for 10 seconds, if equipped.
7. Turn the A/C OFF for 10 seconds, if equipped.
8. If the vehicle is equipped with an automatic trans-
axle, apply the parking brake. While pressing the
brake pedal, place the transaxle in D (drive).
9. Turn the A/C ON for 10 seconds, if equipped.
10. Turn the A/C OFF for 10 seconds, if equipped.
11. Turn the ignition OFF. The idle learn procedure is
complete.

1F – 36IENGINE CONTROLS
DAEWOO V–121 BL4
MULTIPLE ECM INFORMATION SENSOR DTCS SET
Circuit Description
The Engine Control Module (ECM) monitors various sen-
sors to determine engine operating conditions. The ECM
controls fuel delivery, spark advance, transaxle operation,
and emission control device operation based on the sen-
sor inputs.
The ECM provides a sensor ground to all of the sensors.
The ECM applies 5 volts through a pull–up resistor and
monitors the voltage present between the sensor and the
resistor to determine the status of the Engine Coolant
Temperature (ECT) sensor, the Intake Air Temperature
(IAT) sensor. The ECM provides the Exhaust Gas Recir-
culation (EGR) Pintle Position Sensor, the Throttle Posi-
tion (TP) sensor, the Manifold Absolute Pressure (MAP)
sensor, and the Fuel Tank Pressure Sensor with a 5 volt
reference and a sensor ground signal. The ECM monitors
the separate feedback signals from these sensors to de-
termine their operating status.
Diagnostic Aids
Be sure to inspect the ECM and the engine grounds for be-
ing secure and clean.
A short to voltage in one of the sensor circuits can cause
one or more of the following DTCs to be set: P0108,
P0113, P0118, P0123, P1106, P1111, P1115, P1121,
P0463, P0533.
If a sensor input circuit has been shorted to voltage, en-
sure that the sensor is not damaged. A damaged sensor
will continue to indicate a high or low voltage after the af-
fected circuit has been repaired. If the sensor has been
damaged, replace it.
An open in the sensor ground circuit between the ECM and
the splice will cause one or more of the following DTCs to
be set: P0107, P0108, P0113, P0118, P0122, P0123,
P1106, P1111, P1115, P1121, P0462, P0532.
A short to ground in the 5 volt reference circuit or an open
in the 5 volt reference circuit between the ECM and the
splice will cause one or more of the following DTCs to be
set: P0107, P0112, P0117, P0122, P1107, P1112, P1114,
P1122, P0462, P0532.Check for the following conditions:
S Inspect for a poor connection at the ECM. Inspect
harness connectors for backed–out terminals, im-
proper mating, broken locks, improperly formed or
damaged terminals, and poor terminal–to–wire con-
nection.
S Inspect the wiring harness for damage. If the har-
ness appears to be OK, observe an affected sen-
sor ’s displayed value on the scan tool with the igni-
tion ON and the engine OFF while moving
connectors and wiring harnesses related to the af-
fected sensors. A change in the affected sensor’s
displayed value will indicate the location of the fault.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic Table.
1. The Powertrain On–Board Diagnostic (EOBD) Sys-
tem Check prompts the technician to complete
some basic checks and store the freeze frame and
failure records 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.
9. A faulty EGR valve can leak a small amount of cur-
rent from the ignition feed circuit to the 5 volt refer-
ence circuit. If the problem does not exist with the
EGR valve disconnected, replace the EGR valve.
0. If a sensor input circuit has been shorted to voltage,
ensure that the sensor has not been damaged. A
damaged IAT or ECT sensor will continue to indi-
cate a high voltage or low temperature after the
affected circuit has been repaired. A damaged ACT,
TP, MAP, Fuel Tank Pressure, or EGR Pintle Posi-
tion sensor will indicate a high or low voltage or
may be stuck at a fixed value after the affected cir-
cuit has been repaired. If the sensor has been dam-
aged, replace it.
21. The replacement ECM must be reprogrammed.
Refer to the latest Techline procedure for ECM re-
programming.

1F – 38IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
10Replace the EGR valve.
Is the replacement complete?–Go to Step 19–
11Locate and repair the short to voltage in the MAP
sensor signal circuit.
Is the repair complete?–Go to Step 19–
12Locate and repair the short to voltage in the TP sen-
sor signal circuit.
Is the repair complete?–Go to Step 19–
13Locate and repair the short to voltage in the IAT sen-
sor signal circuit.
Is the repair complete?–Go to Step 19–
14Locate and repair the short to voltage in the ECT
sensor signal circuit.
Is the repair complete?–Go to Step 19–
15Locate and repair the short to voltage in the EGR
Pintle Position sensor circuit.
Is the repair complete?–Go to Step 19–
16Measure the voltage of the fuel tank pressure sensor
signal circuit between the ECM harness connector
and ground.
Does the voltage near the specified value?0 VGo to Step 18Go to Step 17
17Locate and repair the short to voltage in the fuel tank
pressure sensor signal circuit.
Is the replacement complete?–Go to Step 19–
18Replace the ECM.
Is the repair complete?–Go to Step 19
191. 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 the DTCs as specified in the supporting
text.
Does the scan tool indicate that this diagnostic ran
and passed?–Go to Step 20Go 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

1F – 42IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
191. Measure the resistance between following ter-
minals:
S Terminal 1 and 2 of ignition coil.
S Terminal 2 and 1 of ignition coil.
Are the resistance within the value specified.
1. Remove the high tension cable.
2. Measure the resistance between second coil.
S Between 1 and 4
S Between 2 and 3
Are the resistance within the value specified.0.9 W
5.3 kWGo to Step 21Go to Step 20
20Replace the EI system ignition coil.
Is the repair complete?–Go to Step 2–
211. Check for any damages or poor connection in
ignition wires and repair as needed.
2. Connect the EI system ignition coil connector
and ECM connector.
3. Check for the presence of spark from all of the
ignition wires.
Is the spark present from all of the ignition wires?–Go to Step 2Go to Step 22
22Replace ECM.
Is the repair complete?–Go to Step 2–
231. Turn the ignition OFF.
2. Connect a fuel pressure gauge.
3. Crank the engine.
Is any fuel pressure present?–Go to Step 26Go to Step 24
241. Turn the ignition OFF.
2. Disconnect the electrical connector at the fuel
pump.
3. Connect a test light between the fuel pump ter-
minals 2 and 3.
4. Turn the ignition ON.
5. With the ignition ON, the test light should light
for the time specified.
Is the test light on?2 sec.Go to Step 25Go to 34
25Replace the fuel pump.
Is the repair complete?–Go to Step 2–
26Is the fuel pressure within the value specified?283–324 kPa
(41–47 psi)Go to Step 27Go to Step 29
27Check the fuel for contamination.
Is the fuel contaminated?–Go to Step 28Go to Step 41
281. Remove the contaminated fuel from the fuel
tank.
2. Clean the fuel tank as needed.
Is the repair complete?–Go to Step 2–
291. Check the fuel filter for restriction.
2. Inspect the fuel lines for kinks and restrictions.
3. Repair or replace as needed.
4. Measure the fuel pressure.
Is the fuel pressure within the value specified?283–324 kPa
(41–47 psi)Go to Step 2Go to Step 30

ENGINE CONTROLS 1F – 43
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
301. Disconnect vacuum line from the fuel pressure
regulator.
2. Inspect the vacuum line for the presence of
fuel.
3. Inspect the fuel pressure regulator vacuum port
for the presence of fuel.
Is any fuel present?–Go to Step 31Go to Step 32
31Replace the fuel pressure regulator.
Is the repair complete?–Go to Step 2–
321. Remove the fuel pump assembly from the fuel
tank.
2. Inspect the fuel pump sender and the fuel cou-
pling hoses for a restriction.
3. Inspect the in–tank fuel filter for restriction.
Is the problem found?–Go to Step 33Go to Step 25
33Replace the fuel pump sender, the in–tank fuel filter,
and/or the fuel coupling hoses as needed.
Is the repair complete?–Go to Step 2–
341. Turn the ignition OFF.
2. Disconnect the electric connector at the fuel
pump.
3. Connect a test light between fuel pump con-
nector terminal 3 and ground.
4. Turn the ignition ON.
5. With the ignition ON, the test light should illumi-
nate for the time specified.
Is the test light on?2 secGo to Step 35Go to Step 36
35Repair the open circuit between the fuel pump con-
nector terminal 2 and ground.
Is the repair complete?–Go to Step 2–
361. Turn the ignition OFF.
2. Disconnect the fuel pump relay.
3. Turn the ignition ON.
4. Measure the voltage at terminal 30 and 86 of
fuel pump relay.
Is the voltage within the value specified?11–14 VGo to Step 38Go to Step 37
37Repair open or short circuit for power supply.
Is the repair complete?–Go to Step 2–
381. Turn the ignition OFF.
2. Disconnect ECM connector.
3. Using an ohmmeter, measure the resistance
between following terminals.
S Terminal 6 of ECM and terminal 85 of fuel
pump relay.
S Terminal 87 of fuel pump relay and terminal
3 of fuel pump.
Does the resistance within the value specified?0 WGo to Step 40Go to Step 39

ENGINE CONTROLS 1F – 51
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
471. Disconnect the vacuum line from the fuel pres-
sure regulator.
2. Inspect the vacuum line for the presence of
fuel.
3. Inspect the fuel pressure regulator vacuum port
for the presence of fuel.
Is any fuel presen–Go to Step 50Go to Step 51
48Check the fuel for contamination.
Is the fuel contaminated?–Go to Step 49Go to Step 65
491. Remove the contaminated fuel from the fuel
tank.
2. Clean the fuel tank as needed.
Is the repair complete?–Go to Step 3–
50Replace the fuel pressure regulator.
Is the repair complete?–Go to Step 3–
511. Remove the fuel pump assembly from the fuel
tank.
2. Inspect the fuel pump sender and the fuel cou-
pling hoses for a restriction.
3. Inspect the in–tank fuel filter for a restriction.
Is the problem found?–Go to Step 52Go to Step 43
52Replace the fuel pump sender, the in–tank fuel filter,
and/or the fuel coupling hoses as needed.
Is the repair complete?–Go to Step 3–
531. Turn the ignition OFF.
2. Disconnect the electrical connector at the fuel
pump.
3. Connect a test light between the fuel pump
connector terminal 3 and a known good
ground.
4. Turn the ignition ON.
5. With the ignition ON, the test light should light
for the time specified.
Is the test light on?2 secGo to Step 54Go to Step 55
54Repair the open wire between the fuel pump connec-
tor terminal 2 and ground.
Is the repair complete–Go to Step 3–
551. Turn the ignition OFF.
2. Disconnect the fuel pump relay.
3. Connect a test light between the fuel pump
relay connector terminal 85 and ground.
4. Turn the ignition ON.
Is the test light on?2 secGo to Step 56Go to Step 62
561. Turn the ignition OFF.
2. Connect a test light between the fuel pump
relay connector terminal 86 and battery posi-
tive.
3. Turn the ignition ON.
4. With the ignition ON, the test light should light
for the time specified.
Is the test light on?–Go to Step 57Go to Step 61

1F – 62IENGINE CONTROLS
DAEWOO V–121 BL4
FUEL SYSTEM DIAGNOSIS
Circuit Description
The fuel pump is an in–tank type mounted to a fuel sender
assembly. The fuel pump will remain on as long as the en-
gine is cranking or running and the Engine Control Module
(ECM) is receiving reference pulses from the crankshaft
position (CKP) sensor. If there are no reference pulses,
the ECM will turn off the fuel pump two seconds after the
ignition switch is turned ON or two seconds after the en-
gine stops running. The fuel pump delivers fuel to the fuel
rail and the fuel injectors, where the fuel system pressure
is controlled from 284 to 325 kPa (41 to 47 psi) by the fuel
pressure regulator. The excess fuel is returned to the fuel
tank.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. When the engine is idling, the intake manifold vacu-
um is high. This vacuum is applied to the fuel pres-
sure regulator diaphragm, offsetting the spring
pressure inside the fuel pressure regulator and low-
ering the fuel pressure.10. If there is fuel bleeding back through the fuel return
outlet, this is due to a faulty fuel pressure regulator.
14. Another symptom often present when the fuel injec-
tors are leaking is hard starting. Leaking fuel injec-
tors can cause a flooding condition.
23. Fuel leaking from the fuel pump inlet is due to a
faulty one–way check valve in the fuel pump.
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.
CAUTION : Do not pinch or restrict nylon fuel lines to
avoid damage that could cause a fuel leak, resulting
in possible fire or personal injury.
Fuel Pressure Relief Procedure
1. Remove the fuel cap.
2. Remove the fuel pump fuse EF18 from the engine
fuse box.
3. Start the engine and allow the engine to stall.
4. Crank the engine for an additional 10 seconds.
Fuel System Diagnosis
StepActionValue(s)YesNo
11. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified and
holding steady?284~325 kPa
(41~47psi)Go to Step 2Go to Step 4
21. Allow the engine to idle.
2. Disconnect the vacuum hose from the fuel
pressure regulator.
3. Connect a vacuum pump with a gauge to the
fuel pressure regulator vacuum port.
4. Apply 41~47 kPa (12~14 in. Hg) of vacuum to
the fuel pressure regulator.
Does the fuel pressure decrease?–Go to Step 3Go to Step 15
31. Locate and correct the cause of the vacuum
restriction to the fuel pressure regulator.
2. Confirm the operation of the fuel pressure reg-
ulator.
Is the repair complete?–System OK–
41. Relieve the fuel system pressure.
2. Install a fuel pressure gauge.
3. Turn the ignition ON.
Is the fuel pressure within the values specified but
not holding steady?284~325 kPa
(41~47psi)Go to Step 5Go to Step 16
5Inspect the fuel lines for a leak.
Is the problem found?–Go to Step 6Go to Step 7