ECU DAEWOO MATIZ 2003 Service Repair Manual

ENGINE COOLING 1D–11
DAEWOO M-150 BL2
D102D505
Installation Procedure
1. Install the surge tank to the vehicle.
Install the surge tank with pressing down (1).
Connect the overflow hoses to the surge tank (2).
2. Secure the overflow hoses to the surge tank with the
hose clamps.
3. Fill the surge tank with coolant to the MAX mark.
D102D506
ELECTRIC COOLING FAN
Removal Procedure
1. Disconnect the negative battery cable.
2. Remove the electric cooling fan assembly.
Disconnect the cooling fan electrical connector (1).
Remove the bolts (2).
Remove the electric cooling fan assembly (3).
3.5–4.5 Nm
D12D507A
Installation Procedure
1. Install the electric cooling fan assembly with the bolts.
Tighten
Tighten the bolts to 3.5–4.5 Nm (31–40 lb-in).
2. Connect the cooling fan electrical connector.
3. Connect the negative battery cable.
D12D5081
RADIATOR
Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect the lower radiator hose and drain the en-
gine cooling system. Refer to “Draining and Refilling
the Cooling System” in this section.
3. Disconnect the upper radiator hose and the surge
tank hose.
Loosen the upper radiator hose clamp and discon-
nect the upper radiator hose (1).
Loosen the surge tank hose clamp and disconnect
the surge tank hose (2).

1D–12 ENGINE COOLING
DAEWOO M-150 BL2
D12D5091
4. Remove the electric cooling fan.
Refer to “Electric Cooling Fan” in this section.
5. Remove the radiator.
Remove the bolts (1).
Remove the radiator support brackets (2).
Remove the radiator (3).
6. Check the radiator for breaking, clog or other dam-
age.
Important: The radiator still contains a substantial
amount of coolant. Drain the remainder of the coolant
from the radiator into a drain pan.
D12D5101
Installation Procedure
1. Install the radiator with the mounting bolts (1) and the
support brackets (2).
Tighten
Tighten the support bracket bolts to 3.5–4.5 Nm
(31–40 lb-in).
2. Install the electric cooling fan.
Refer to “Electric Cooling Fan” in this section.
D12D5111
3. Connect the upper radiator hose to the radiator (1).
4. Connect the surge tank hose to the radiator (2).
5. Secure each hose with hose clamps.
6. Refill the engine cooling system. Refer to “Draining
and Refilling the Cooling System” in this section.
7. Connect the negative battery cable.
D102D512
THERMOSTAT (TYPICAL)
Removal Procedure
Caution: To prevent personal injury, do not remove
the surge tank cap while the engine and the radiator
are hot because the heat causes the system to re-
main under pressure. Scalding fluid and steam may
be blown out under pressure.
1. Remove air filter assembly. Refer to Section 1B,
SOHC Engine Mechanical.
2. Disconnect the lower radiator hose and drain the
coolant. Refer to “Drain and Refilling the Cooling Sys-
tem”
3. Disconnect the upper radiator hose.

ENGINE COOLING 1D–13
DAEWOO M-150 BL2
Loosen the hose clamp (1).
Disconnect the upper radiator hose (2).
D102D513
4. Remove the thermostat.
Remove the bolts (1).
Remove the thermostat housing (2).
Remove the thermostat with the gasket (3).
5. Check the gasket for crack or other damage.
6. Inspect the valve seat for foreign matter that could
prevent the valve from seating properly.
7. Inspect the thermostat for proper operation. Refer to
“Thermostat Test” in this section.
8–15 Nm
D12D514A
Installation Procedure
1. Install the thermostat with the bolts and the thermo-
stat housing.
Tighten
Tighten the mounting bolts to 8–15 Nm (71–130
lb-in).
2. Secure the upper radiator hose to the thermostat
housing with a hose clamp.
3. Refill the engine cooling system. Refer to “Draining
and Refilling the Cooling System” in this section.
MAA1D010
THERMOSTAT (EURO III)
Removal Procedure
Caution: To prevent personal injury, do not remove
the surge tank cap while the engine and the radiator
are hot because the heat causes the system to re-
main under pressure. Scalding fluid and steam may
be blown out under pressure.
1. Remove air filter assembly. Refer to Section 1B,
SOHC Engine Mechanical.
2. Disconnect the lower radiator hose and drain the
coolant. Refer to “Drain and Refilling the Cooling Sys-
tem”
3. Disconnect the upper radiator hose.

1D–14 ENGINE COOLING
DAEWOO M-150 BL2
MAA1D020
4. Remove the thermostat.
Remove the bolts.
Remove the thermostat housing.
Remove the thermostat with the gasket.
5. Check the gasket for crack or other damage.
6. Inspect the valve seat for foreign matter that could
prevent the valve from seating properly.
7. Inspect the thermostat for proper operation. Refer to
“Thermostat Test” in this section.
MAA1D011
Installation Procedure
1. Install the thermostat with the bolts and the thermo-
stat housing.
Tighten
Tighten the mounting bolts to 8–15 Nm (71–130
lb-in).
2. Secure the upper radiator hose to the thermostat
housing with a hose clamp.
3. Refill the engine cooling system. Refer to “Draining
and Refilling the Cooling System” in this section.
4. Install the air filter assembly. Refer to Section 1B,
SOHC Engine Mechanical.
D102D515
COOLANT TEMPERATURE SENSOR
Removal Procedure
1. Disconnect the negative battery cable.
2. Disconnect the lower radiator hose and drain the
coolant. Refer to “Draining and Refilling the Cooling
System” in this section.
3. Remove the coolant temperature sensor.
Disconnect the electrical connector (1).
Remove the coolant temperature sensor (2).
D12D516A
10 Nm
Installation Procedure
1. Install the coolant temperature sensor into the
threaded hole in the intake manifold.
Tighten
Tighten the coolant temperature sensor to 10 Nm
(89 lb-in).
Connect the electrical connector to the coolant
temperature sensor (1).
2. Connect the lower radiator hose and refill the coolant.
Refer to “Draining and refilling the cooling system” in
this section.
3. Connect the negative battery cable.

1F–10 ENGINE CONTROLS
DAEWOO M-150 BL2
fuels use alcohol to increase the octane rating of the
fuel. Although alcohol-enhanced fuels may raise the oc-
tane rating, the fuel’s ability to turn into vapor in cold
temperatures deteriorates. This may affect the starting
ability and cold driveability of the engine.
Low fuel levels can lead to fuel starvation, lean engine
operation, and eventually engine misfire.
Non-OEM Parts
The EOBD system has been calibrated to run with Origi-
nal Equipment Manufacturer (OEM) parts. Something
as simple as a high performance-exhaust system that
affects exhaust system back pressure could potentially
interfere with the operation of the Electric Exhaust Gas
Recirculation (EEGR) valve and thereby turn on the
MIL. Small leaks in the exhaust system near the heated
oxygen sensor (HO2S) can also cause the MIL to turn
on.
Aftermarket electronics, such as cellular phones, ster-
eos, and anti-theft devices, may radiate Electromagnet-
ic Interference (EMI) into the control system if they are
improperly installed. This may cause a false sensor
reading and turn on the MIL.
Environment
Temporary environmental conditions, such as localized
flooding, will have an effect on the vehicle ignition sys-
tem. If the ignition system is rain-soaked, it can tempo-
rarily cause engine misfire and turn on the MIL.
Vehicle Marshaling
The transportation of new vehicles from the assembly
plant to the dealership can involve as many as 60 key
cycles within 2 to 3 miles of driving. This type of opera-
tion contributes to the fuel fouling of the spark plugs and
will turn on the MIL with a set DTC P0300.
Poor Vehicle Maintenance
The sensitivity of the EOBD will cause the MIL to turn on
if the vehicle is not maintained properly. Restricted air fil-
ters, fuel filters, and crankcase deposits due to lack of oil
changes or improper oil viscosity can trigger actual ve-
hicle faults that were not previously monitored prior to
EOBD. Poor vehicle maintenance can not be classified
as a “non-vehicle fault,” but with the sensitivity of the
EOBD, vehicle maintenance schedules must be more
closely followed.
Severe Vibration
The Misfire diagnostic measures small changes in the
rotational speed of the crankshaft. Severe driveline
vibrations in the vehicle, such as caused by an exces-
sive amount of mud on the wheels, can have the same
effect on crankshaft speed as misfire and, therefore,
may set DTC P0300.
Related System Faults
Many of the EOBD system diagnostics will not run if the
Engine Control Module (ECM) detects a fault on a re-
lated system or component. One example would be thatif the ECM detected a Misfire fault, the diagnostics on
the catalytic converter would be suspended until the
Misfire fault was repaired. If the Misfire fault is severe
enough, the catalytic converter can be damaged due to
overheating and will never set a Catalyst DTC until the
Misfire fault is repaired and the Catalyst diagnostic is al-
lowed to run to completion. If this happens, the custom-
er may have to make two trips to the dealership in order
to repair the vehicle.
SERIAL DATA COMMUNICATIONS
Keyword 2000 Serial Data
Communications
Government regulations require that all vehicle
manufacturers establish a common communication sys-
tem. This vehicle utilizes the “Keyword 2000” commu-
nication system. Each bit of information can have one of
two lengths: long or short. This allows vehicle wiring to
be reduced by transmitting and receiving multiple sig-
nals over a single wire. The messages carried on Key-
word 2000 data streams are also prioritized. If two
messages attempt to establish communications on the
data line at the same time, only the message with higher
priority will continue. The device with the lower priority
message must wait. The most significant result of this
regulation is that it provides scan tool manufacturers
with the capability to access data from any make or
model vehicle that is sold.
The data displayed on the other scan tool will appear the
same, with some exceptions. Some scan tools will only
be able to display certain vehicle parameters as values
that are a coded representation of the true or actual val-
ue. On this vehicle, the scan tool displays the actual val-
ues for vehicle parameters. It will not be necessary to
perform any conversions from coded values to actual
values.
EURO ON-BOARD DIAGNOSTIC
(EOBD)
Euro On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which
is a pass or fail reported to the diagnostic executive.
When a diagnostic test reports a pass result, the diag-
nostic executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The diagnostic test has passed during the current
ignition cycle.

The fault identified by the diagnostic test is not cur-
rently active.
When a diagnostic test reports a fail result, the diagnos-
tic executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

1F–12 ENGINE CONTROLS
DAEWOO M-150 BL2
The enable criteria for each diagnostic is listed on the
first page of the Diagnostic Trouble Code (DTC) descrip-
tion under the heading “Conditions for Setting the DTC.”
Enable criteria varies with each diagnostic and typically
includes, but is not limited to the following items:

Engine speed.

Vehicle speed

Engine Coolant Temperature (ECT)

Manifold Absolute Pressure (MAP)

Barometric Pressure (BARO)

Intake Air Temperature (IAT)

Throttle Position (TP)

High canister purge

Fuel trim

A/C on
Trip
Technically, a trip is a key-on run key-off cycle in which
all the enable criteria for a given diagnostic are met, al-
lowing the diagnostic to run. Unfortunately, this concept
is not quite that simple. A trip is official when all the en-
able criteria for a given diagnostic are met. But because
the enable criteria vary from one diagnostic to another,
the definition of trip varies as well. Some diagnostics are
run when the vehicle is at operating temperature, some
when the vehicle first starts up; some require that the
vehicle cruise at a steady highway speed, some run only
when the vehicle is at idle. Some run only immediately
following a cold engine start-up.
A trip then, is defined as a key-on run-key off cycle in
which the vehicle is operated in such a way as to satisfy
the enable criteria for a given diagnostic, and this diag-
nostic will consider this cycle to be one trip. However,
another diagnostic with a different set of enable criteria
(which were not met) during this driving event, would not
consider it a trip. No trip will occur for that particular
diagnostic until the vehicle is driven in such a way as to
meet all the enable criteria.
Diagnostic Information
The diagnostic charts and functional checks are de-
signed to locate a faulty circuit or component through a
process of logical decisions. The charts are prepared
with the requirement that the vehicle functioned correct-
ly at the time of assembly and that there are not multiple
faults present.
There is a continuous self-diagnosis on certain control
functions. This diagnostic capability is complimented by
the diagnostic procedures contained in this manual. The
language of communicating the source of the malfunc-
tion is a system of diagnostic trouble codes. When a
malfunction is detected by the control module, a DTC is
set, and the Malfunction Indicator Lamp (MIL) is illumi-
nated.
Malfunction Indicator Lamp (MIL)
The Malfunction Indicator Lamp (MIL) is required by
Euro On-Board Diagnostics (EOBD) to illuminate under
a strict set of guidelines.
Basically, the MIL is turned on when the Engine Control
Module (ECM) detects a DTC that will impact the vehicle
emissions.
The MIL is under the control of the Diagnostic Execu-
tive. The MIL will be turned on if an emissions-related
diagnostic test indicates a malfunction has occurred. It
will stay on until the system or component passes the
same test for three consecutive trips with no emissions
related faults.
Extinguishing the MIL
When the MIL is on, the Diagnostic Executive will turn
off the MIL after three consecutive trips that a “test
passed” has been reported for the diagnostic test that
originally caused the MIL to illuminate. Although the MIL
has been turned off, the DTC will remain in the ECM
memory (both Freeze Frame and Failure Records) until
forty (40) warm-up cycles after no faults have been com-
pleted.
If the MIL was set by either a fuel trim or misfire-related
DTC, additional requirements must be met. In addition
to the requirements stated in the previous paragraph,
these requirements are as follows:

The diagnostic tests that are passed must occur with
375 rpm of the rpm data stored at the time the last
test failed.

Plus or minus ten percent of the engine load that was
stored at the time the last test failed. Similar engine
temperature conditions (warmed up or warming up)
as those stored at the time the last test failed.
Meeting these requirements ensures that the fault which
turned on the MIL has been corrected.
The MIL is on the instrument panel and has the following
functions:

It informs the driver that a fault affecting the vehicle’s
emission levels has occurred and that the vehicle
should be taken for service as soon as possible.

As a system check, the MIL will come on with the key
ON and the engine not running. When the engine is
started, the MIL will turn OFF.

When the MIL remains ON while the engine is run-
ning, or when a malfunction is suspected due to a
driveability or emissions problem, an EOBD System
Check must be performed. The procedures for these
checks are given in EOBD System Check. These
checks will expose faults which may not be detected
if other diagnostics are performed first.

ENGINE CONTROLS 1F–13
DAEWOO M-150 BL2
Data Link Connector (DLC)
The provision for communicating with the control mod-
ule is the Data Link Connector (DLC). The DLC is used
to connect to a scan tool. Some common uses of the
scan tool are listed below:

Identifying stored DTCs.

Clearing DTCs.

Performing output control tests.

Reading serial data.
DTC TYPES
Each Diagnostic Trouble Code (DTC) is directly related
to a diagnostic test. The Diagnostic Management Sys-
tem sets DTCs based on the failure of the tests during a
trip or trips. Certain tests must fail two consecutive trips
before the DTC is set. The following are the three types
of DTCs and the characteristics of those codes:
Type A

Emissions related.

Requests illumination of the Malfunction Indicator.
Lamp (MIL) of the first trip with a fail.

Stores a History DTC on the first trip with a fail.

Stores a Freeze Frame (if empty).

Stores a Fail Record.

Updates the Fail Record each time the diagnostic test
fails.
Type B

Emissions related.

“Armed” after one trip with a fail.

“Disarmed” after one trip with a pass.

Requests illumination of the MIL on the second con-
secutive trip with a fail.

Stores a History DTC on the second consecutive trip
with a fail (The DTC will be armed after the first fail).

Stores a Freeze Frame on the second consecutive
trip with a fail (if empty).
Type Cnl

Non-Emissions related.

Does not request illumination of any lamp.

Stores a History DTC on the first trip with a fail .

Does not store a Freeze Frame.

Stores Fail Record when test fails.

Updates the Fail Record each time the diagnostic test
fails.
Type E

Emissions related.

“Armed” after two consecutive trip with a fail.

“Disarmed” after one trip with a pass.
Requests illumination of the MIL on the third consec-
utive trip with a fail.

Stores a History DTC on the third consecutive trip
with a fail (The DTC will be armed after the second
fail).

Stores a Freeze Frame on the third consecutive trip
with a fail (if empty).
Important: For 0.8 SOHC engine eight fail records can
be stored. Each Fail Record is for a different DTC. It is
possible that there will not be Fail Records for every
DTC if multiple DTCs are set.
Special Cases of Type B Diagnostic Tests
Unique to the misfire diagnostic, the Diagnostic Execu-
tive has the capability of alerting the vehicle operator to
potentially damaging levels of misfire. If a misfire condi-
tion exists that could potentially damage the catalytic
converter as a result of high misfire levels, the Diagnos-
tic Executive will command the MIL to “flash” as a rate of
once per seconds during those the time that the catalyst
damaging misfire condition is present.
Fuel trim and misfire are special cases of Type B diag-
nostics. Each time a fuel trim or misfire malfunction is
detected, engine load, engine speed, and Engine Cool-
ant Temperature (ECT) are recorded.
When the ignition is turned OFF, the last reported set of
conditions remain stored. During subsequent ignition
cycles, the stored conditions are used as a reference for
similar conditions. If a malfunction occurs during two
consecutive trips, the Diagnostic Executive treats the
failure as a normal Type B diagnostic, and does not use
the stored conditions. However, if a malfunction occurs
on two non-consecutive trips, the stored conditions are
compared with the current conditions. The MIL will then
illuminate under the following conditions:

When the engine load conditions are within 10% of
the previous test that failed.

Engine speed is within 375 rpm, of the previous test
that failed.

ECT is in the same range as the previous test that
failed.
READING DIAGNOSTIC TROUBLE
CODES
The procedure for reading Diagnostic Trouble Code(s)
(DTC) is to use a diagnostic scan tool. When reading
DTC(s), follow instructions supplied by tool manufactur-
er.
Clearing Diagnostic Trouble Codes
Important: Do not clear DTCs unless directed to do so
by the service information provided for each diagnostic
procedure. When DTCs are cleared, the Freeze Frame
and Failure Record data which may help diagnose an in-

1F–14 ENGINE CONTROLS
DAEWOO M-150 BL2
termittent fault will also be erased from memory. If the
fault that caused the DTC to be stored into memory has
been corrected, the Diagnostic Executive will begin to
count the ‘‘warm-up” cycles with no further faults de-
tected, the DTC will automatically be cleared from the
Engine Control Module (ECM) memory.
To clear DTCs, use the diagnostic scan tool.
It can’t cleared DTCs without the diagnostic scan tool.
So you must use the diagnostic scan tool.
Notice: To prevent system damage, the ignition key
must be OFF when disconnecting or reconnecting bat-
tery power.

The power source to the control module. Examples:
fuse, pigtail at battery ECM connectors, etc.

The negative battery cable. (Disconnecting the nega-
tive battery cable will result in the loss of other Euro
On-Board memory data, such as preset radio tuning.)
DTC Modes
On Euro On-Board Diagnostic (EOBD) passenger cars
there are five options available in the scan tool DTC
mode to display the enhanced information available. A
description of the new modes, DTC Info and Specific
DTC, follows. After selecting DTC, the following menu
appears:

DTC Info.

Specific DTC.

Freeze Frame.

Fail Records (not all applications).

Clear Info.
The following is a brief description of each of the sub
menus in DTC Info and Specific DTC. The order in
which they appear here is alphabetical and not neces-
sarily the way they will appear on the scan tool.
DTC Information Mode
Use the DTC info mode to search for a specific type of
stored DTC information. There are seven choices. The
service manual may instruct the technician to test for
DTCs in a certain manner. Always follow published ser-
vice procedures.
To get a complete description of any status, press the
‘‘Enter” key before pressing the desired F-key. For ex-
ample, pressing ‘‘Enter” then an F-key will display a defi-
nition of the abbreviated scan tool status.
DTC Status
This selection will display any DTCs that have not run
during the current ignition cycle or have reported a test
failure during this ignition up to a maximum of 33 DTCs.
DTC tests which run and pass will cause that DTC num-
ber to be removed from the scan tool screen.
Fail This Ign. (Fail This Ignition)
This selection will display all DTCs that have failed dur-
ing the present ignition cycle.
History
This selection will display only DTCs that are stored in
the ECM’s history memory. It will not display Type B
DTCs that have not requested the Malfunction Indicator
Lamp (MIL). It will display all type A, B and E DTCs that
have requested the MIL and have failed within the last
40 warm-up cycles. In addition, it will display all type C
and type D DTCs that have failed within the last 40
warm-up cycles.
Last Test Fail
This selection will display only DTCs that have failed the
last time the test ran. The last test may have run during
a previous ignition cycle if a type A or type B DTC is dis-
played. For type C and type D DTCs, the last failure
must have occurred during the current ignition cycle to
appear as Last Test Fail.
MIL Request
This selection will display only DTCs that are requesting
the MIL. Type C and type D DTCs cannot be displayed
using this option. This selection will report type B and E
DTCs only after the MIL has been requested.
Not Run SCC (Not Run Since Code Clear)
This option will display up to 33 DTCs that have not run
since the DTCs were last cleared. Since the displayed
DTCs have not run, their condition (passing or failing) is
unknown.
Test Fail SCC (Test Failed Since Code
Clear)
This selection will display all active and history DTCs
that have reported a test failure since the last time DTCs
were cleared. DTCs that last failed more than 40 warm-
up cycles before this option is selected will not be dis-
played.
Specific DTC Mode
This mode is used to check the status of individual diag-
nostic tests by DTC number. This selection can be ac-
cessed if a DTC has passed, failed or both. Many EOBD
DTC mode descriptions are possible because of the ex-
tensive amount of information that the diagnostic execu-
tive monitors regarding each test. Some of the many
possible descriptions follow with a brief explanation.
The “F2” key is used, in this mode, to display a descrip-
tion of the DTC. The “Ye s” and “No” keys may also be
used to display more DTC status information. This
selection will only allow entry of DTC numbers that are
supported by the vehicle being tested. If an attempt is,

ENGINE CONTROLS 1F–15
DAEWOO M-150 BL2
made to enter DTC numbers for tests which the diag-
nostic executive does not recognize, the requested in-
formation will not be displayed correctly and the scan
tool may display an error message. The same applies to
using the DTC trigger option in the Snapshot mode. If an
invalid DTC is entered, the scan tool will not trigger.
Failed Last Test
This message display indicates that the last diagnostic
test failed for the selected DTC. For type A, B and E
DTCs, this message will be displayed during subse-
quent ignition cycles until the test passes or DTCs are
cleared. For type C and type D DTCs, this message will
clear when the ignition is cycled.
Failed Since Clear
This message display indicates that the DTC has failed
at least once within the last 40 warm-up cycles since the
last time DTCs were cleared.
Failed This Ig. (Failed This Ignition)
This message display indicates that the diagnostic test
has failed at least once during the current ignition cycle.
This message will clear when DTCs are cleared or the
ignition is cycled.
History DTC
This message display indicates that the DTC has been
stored in memory as a valid fault. A DTC displayed as a
History fault may not mean that the fault is no longer
present. The history description means that all the con-
ditions necessary for reporting a fault have been met
(maybe even currently), and the information was stored
in the control module memory.
MIL Requested
This message display indicates that the DTC is currently
causing the MIL to be turned ON. Remember that only
type A B and E DTCs can request the MIL. The MIL re-
quest cannot be used to determine if the DTC fault con-
ditions are currently being experienced. This is because
the diagnostic executive will require up to three trips dur-
ing which the diagnostic test passes to turn OFF the
MIL.
Not Run Since CI (Not Run Since Cleared)
This message display indicates that the selected diag-
nostic test has not run since the last time DTCs were
cleared. Therefore, the diagnostic test status (passing
or failing) is unknown. After DTCs are cleared, this mes-
sage will continue to be displayed until the diagnostic
test runs.
Not Run This Ig. (Not Run This Ignition)
This message display indicates that the selected diag-
nostic test has not run during this ignition cycle.
Test Ran and Passed
This message display indicates that the selected diag-
nostic test has done the following:
Passed the last test.

Run and passed during this ignition cycle.

Run and passed since DTCs were last cleared.
If the indicated status of the vehicle is “Test Ran and
Passed” after a repair verification, the vehicle is ready to
be released to the customer.
If the indicated status of the vehicle is “Failed This Igni-
tion” after a repair verification, then the repair is incom-
plete and further diagnosis is required.
Prior to repairing a vehicle, status information can be
used to evaluate the state of the diagnostic test, and to
help identify an intermittent problem. The technician can
conclude that although the MIL is illuminated, the fault
condition that caused the code to set is not present. An
intermittent condition must be the cause.
PRIMARY SYSTEM-BASED
DIAGNOSTICS
There are primary system-based diagnostics which
evaluate the system operation and its effect on vehicle
emissions. The primary system-based diagnostics are
listed below with a brief description of the diagnostic
function:
Oxygen Sensor Diagnosis
The fuel control oxygen sensor (O2S) is diagnosed for
the following conditions:

Few switch count (rich to lean or lean to rich).

Slow response (average transient time lean to rich or
rich to lean).

Response time ratio (ratio of average transient time
rich(lean) to lean(rich)).

Inactive signal (output steady at bias voltage approxi-
mately 450 mV).

Signal fixed high.

Signal fixed low.
The catalyst monitor heated oxygen sensor (HO2S) is
diagnosed for the following conditions:

Heater performance (current during IGN on).

Signal fixed low during steady state conditions or
power enrichment (hard acceleration when a rich mix-
ture should be indicated).

Signal fixed high during steady state conditions or de-
celeration mode (deceleration when a lean mixture
should be indicated).

Inactive sensor (output steady at approx. 438 mV).
If the O2S pigtail wiring, connector or terminal are dam-
aged, the entire O2S assembly must be replaced. Do
not attempt to repair the wiring, connector or terminals.
In order for the sensor to function properly, it must have
clean reference air provided to it. This clean air refer-
ence is obtained by way of the O2S wire(s). Any attempt
to repair the wires, connector or terminals could result in

1F–16 ENGINE CONTROLS
DAEWOO M-150 BL2
the obstruction of the reference air and degrade the O2S
performance.
Misfire Monitor Diagnostic Operation
The misfire monitor diagnostic is based on crankshaft
rotational velocity (reference period) variations. The En-
gine Control Module (ECM) determines crankshaft rota-
tional velocity using the Crankshaft Position (CKP)
sensor and the Camshaft Position (CMP) sensor. When
a cylinder misfires, the crankshaft slows down momen-
tarily. By monitoring the CKP and CMP sensor signals,
the ECM can calculate when a misfire occurs.
For a non-catalyst damaging misfire, the diagnostic will
be required to monitor a misfire present for between
1000–3200 engine revolutions.
For catalyst-damaging misfire, the diagnostic will re-
spond to misfire within 200 engine revolutions.
Rough roads may cause false misfire detection. A rough
road will cause torque to be applied to the drive wheels
and drive train. This torque can intermittently decrease
the crankshaft rotational velocity. This may be falsely
detected as a misfire.
A rough road sensor, or “G sensor,” works together with
the misfire detection system. The rough road sensor
produces a voltage that varies along with the intensity of
road vibrations. When the ECM detects a rough road,
the misfire detection system is temporarily disabled.
Misfire Counters
Whenever a cylinder misfires, the misfire diagnostic
counts the misfire and notes the crankshaft position at
the time the misfire occurred. These “misfire counters”
are basically a file on each engine cylinder. A current
and a history misfire counter are maintained for each
cylinder. The misfire current counters (Misfire Current
#1–4) indicate the number of firing events out of the last
200 cylinder firing events which were misfires. The mis-
fire current counter will display real time data without a
misfire DTC stored. The misfire history counters (Misfire
Histtory #1–4) indicate the total number of cylinder firing
events which were misfires. The misfire history counters
will display 0 until the misfire diagnostic has failed and a
DTC P0300 is set. Once the misfire DTC P0300 is set,
the misfire history counters will be updated every 200
cylinder firing events. A misfire counter is maintained for
each cylinder.
If the misfire diagnostic reports a failure, the diagnostic
executive reviews all of the misfire counters before re-
porting a DTC. This way, the diagnostic executive re-
ports the most current information.
When crankshaft rotation is erratic, a misfire condition
will be detected. Because of this erratic condition, the
data that is collected by the diagnostic can sometimes
incorrectly identify which cylinder is misfiring.
Use diagnostic equipment to monitor misfire counter
data on EOBD compliant vehicles. Knowing which spe-
cific cylinder(s) misfired can lead to the root cause, evenwhen dealing with a multiple cylinder misfire. Using the
information in the misfire counters, identify which cylin-
ders are misfiring. If the counters indicate cylinders
numbers 1 and 4 misfired, look for a circuit or compo-
nent common to both cylinders number 1 and 4.
The misfire diagnostic may indicate a fault due to a tem-
porary fault not necessarily caused by a vehicle emis-
sion system malfunction. Examples include the following
items:

Contaminated fuel.

Low fuel.

Fuel-fouled spark plugs.

Basic engine fault.
Fuel Trim System Monitor Diagnostic
Operation
This system monitors the averages of short-term and
long-term fuel trim values. If these fuel trim values stay
at their limits for a calibrated period of time, a malfunc-
tion is indicated. The fuel trim diagnostic compares the
averages of short-term fuel trim values and long-term
fuel trim values to rich and lean thresholds. If either val-
ue is within the thresholds, a pass is recorded. If both
values are outside their thresholds, a rich or lean DTC
will be recorded.
The fuel trim system diagnostic also conducts an intru-
sive test. This test determines if a rich condition is being
caused by excessive fuel vapor from the controlled char-
coal canister. In order to meet EOBD requirements, the
control module uses weighted fuel trim cells to deter-
mine the need to set a fuel trim DTC. A fuel trim DTC
can only be set if fuel trim counts in the weighted fuel
trim cells exceed specifications. This means that the ve-
hicle could have a fuel trim problem which is causing a
problem under certain conditions (i.e., engine idle high
due to a small vacuum leak or rough idle due to a large
vacuum leak) while it operates fine at other times. No
fuel trim DTC would set (although an engine idle speed
DTC or HO2S DTC may set). Use a scan tool to observe
fuel trim counts while the problem is occurring.
A fuel trim DTC may be triggered by a number of vehicle
faults. Make use of all information available (other DTCs
stored, rich or lean condition, etc.) when diagnosing a
fuel trim fault.
Fuel Trim Cell Diagnostic Weights
No fuel trim DTC will set regardless of the fuel trim
counts in cell 0 unless the fuel trim counts in the
weighted cells are also outside specifications. This
means that the vehicle could have a fuel trim problem
which is causing a problem under certain conditions (i.e.
engine idle high due to a small vacuum leak or rough
due to a large vacuum leak) while it operates fine at oth-
er times. No fuel trim DTC would set (although an en-
gine idle speed DTC or HO2S DTC may set). Use a
scan tool to observe fuel trim counts while the problem is
occurring.