2004 DAEWOO LACETTI transaxle

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 – 82IENGINE CONTROLS
DAEWOO V–121 BL4
IDLE AIR CONTROL SYSTEM CHECK (1.8L DOHC)
Circuit Description
The Engine Control Module (ECM) controls the engine idle
speed with the Idle Air Control (IAC) valve. To increase the
idle speed, the ECM pulls the IAC pintle away from its seat,
allowing more air to pass by the throttle body. To decrease
the idle speed, it extends the IAC valve pintle toward its
seat, reducing bypass air flow. A scan tool will read the
ECM commands to the IAC valve in counts. The higher
counts indicate more air bypass (higher idle). The lower
counts indicate less air is allowed to bypass (lower idle).
Diagnostic Aids
If the idle is too high, stop the engine. Fully extend the Idle
Air Control (IAC) valve with a IAC driver. Start the engine.
If the idle speed is above 800 rpm, locate and repair the
vacuum leak. Also, check for a binding throttle plate or
throttle linkage or an incorrect base idle setting.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. The IAC valve is extended and retracted by the IAC
driver. IAC valve movement is verified by an engine
speed change. If no change in engine speed oc-
curs, the valve can be removed from the throttle
body and tested. Connect the IAC driver to the re-
moved IAC valve and turn the ignition ON. Do not
start the engine.5. This step checks the quality of the IAC valve move-
ment in Step 2. Fully extending the IAC valve may
cause an engine stall. This may be normal.
6. Steps 2 and 5 verify proper IAC valve operation.
This step checks the IAC circuit for a wiring or ECM
fault.
Idle Air Control Valve Reset Procedure
Whenever the battery cable or the Engine Control Module
(ECM) connector or the ECM fuse Ef11 is disconnected or
replaced, the following idle learn procedure must be per-
formed:
1. Turn the ignition ON for 5 seconds.
2. Turn the ignition OFF for 10 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.

ENGINE CONTROLS 1F – 171
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0261
INJECTOR 1 LOW VOLTAGE
Circuit Description
The transaxle control module(TCM)/engine control mod-
ule (ECM) has four individual injector 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 mea-
sures a voltage drop through a fixed resistor and controls
it. The voltage on each driver is monitored 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 low voltage and/or an open circuit and high
voltage conditions for low–side drive injector outputs.
Conditions for Setting the DTC
S The injector 1 circuit is an open or a short to ground
condition exists.
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 Records buffers.S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after 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 10 sec-
onds.
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage
will causes a DTC P0261 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–terms 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.
The injector resistance tested at the ECM connection is
slightly more than it tested directly at the injector because
it includes resistance of the harness wires. The normal val-
ue is about 13.5W.

ENGINE CONTROLS 1F – 173
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0262
INJECTOR 1 HIGH VOLTAGE
Circuit Description
The transaxle control module(TCM)/engine control mod-
ule (ECM) has four individual injector 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 mea-
sures a voltage drop through a fixed resistor and controls
it. The voltage on each driver is monitored 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 low voltage and/or an open circuit and high
voltage conditions for low–side drive injector outputs.
Conditions for Setting the DTC
S The injector 1 circuit is a short to battery condition
exists.
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 Records buffers.S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after 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 10 sec-
onds.
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage
will causes a DTC P0262 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–terms 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.
The injector resistance tested at the ECM connection is
slightly more than it tested directly at the injector because
it includes resistance of the harness wires. The normal val-
ue is about 13.5W.

ENGINE CONTROLS 1F – 175
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0264
INJECTOR 2 LOW VOLTAGE
Circuit Description
The transaxle control module(TCM)/engine control mod-
ule (ECM) has four individual injector 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 mea-
sures a voltage drop through a fixed resistor and controls
it. The voltage on each driver is monitored 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 low voltage and/or an open circuit and high
voltage conditions for low–side drive injector outputs.
Conditions for Setting the DTC
S The injector 2 circuit is an open or a short to ground
condition exists.
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 Records buffers.S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after 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 10 sec-
onds.
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage
will causes a DTC P0264 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–terms 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.
The injector resistance tested at the ECM connection is
slightly more than it tested directly at the injector because
it includes resistance of the harness wires. The normal val-
ue is about 13.5W.

ENGINE CONTROLS 1F – 177
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0265
INJECTOR 2 HIGH VOLTAGE
Circuit Description
The transaxle control module(TCM)/engine control mod-
ule (ECM) has four individual injector 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 mea-
sures a voltage drop through a fixed resistor and controls
it. The voltage on each driver is monitored 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 low voltage and/or an open circuit and high
voltage conditions for low–side drive injector outputs.
Conditions for Setting the DTC
S The injector 2 circuit is a short to battery condition
exists.
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 Records buffers.S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after 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 10 sec-
onds.
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage
will causes a DTC P0265 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–terms 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.
The injector resistance tested at the ECM connection is
slightly more than it tested directly at the injector because
it includes resistance of the harness wires. The normal val-
ue is about 13.5W.

ENGINE CONTROLS 1F – 179
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0267
INJECTOR 3 LOW VOLTAGE
Circuit Description
The transaxle control module(TCM)/engine control mod-
ule (ECM) has four individual injector 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 mea-
sures a voltage drop through a fixed resistor and controls
it. The voltage on each driver is monitored 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 low voltage and/or an open circuit and high
voltage conditions for low–side drive injector outputs.
Conditions for Setting the DTC
S The injector 3 circuit is an open or a short to ground
condition exists.
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 Records buffers.S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after 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 10 sec-
onds.
Diagnostic Aids
An injector driver circuit that is open or shorted to voltage
will causes a DTC P0267 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–terms 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.
The injector resistance tested at the ECM connection is
slightly more than it tested directly at the injector because
it includes resistance of the harness wires. The normal val-
ue is about 13.5W.