
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–26 ENGINE CONTROLS
DAEWOO M-150 BL2
Engine Cranks But Will Not Run (Cont’d)
StepActionValue(s)YesNo
12
Check for an open or short in the wires between
CKP sensor connector and ECM connector and
repair as need.
Is the repair complete?
–
Go to Step 2
–
13
1. Disconnect electronic Ignition (EI) system ignition
coil connector to prevent the vehicle from starting.
2. Measure the voltage at ECM connector terminal
24 and 54 by backprobing the ECM connector.
Are the voltage readings near the value specified?
0.4 V with
ignition ON,
2.0 V during
cranking
Go to Step 15Go to Step 14
14Replace the CKP sensor.
Is the repair complete?–Go to Step 2–
15
1. Turn the ignition OFF.
2. Disconnect the electrical connector at EI system
ignition coil.
3. Connect a test light between terminal 1 of the EI
system ignition coil connector and ground.
4. Turn the ignition ON.
Is the test light on?
–
Go to Step 17Go to Step 16
16
Check for open in wire between the battery and EI
system ignition coil connector terminal 1 and repair
as needed.
Is the repair complete?
–
Go to Step 2
–
17
1. Turn the ignition OFF.
2. Disconnect ECM connector and EI system
ignition coil connector.
3. Measure the resistance between following
terminals:
Terminal 2 of ignition coil and terminal 1 of
ECM connector.
Terminal 3 of ignition coil and terminal 32 of
ECM connector.
Terminal 4 of ignition coil and terminal 31 of
ECM connector.
Are the resistance within the value specified?
0 ΩGo to Step 19Go to Step 18
18Check for open circuit and repair as needed.
Is the repair complete?–Go to Step 2–
19
1. Measure the resistance between following
terminals:
Terminal 1 and 2 of ignition coil.
Terminal 3 and 4 of ignition coil.
Are the resistance within the value specified?
2. Remove the high tension cable.
3. Measure the resistance between second coil.
Between 1 and 4
Between 2 and 3
Are the resistance within the value specified?
0.9Ω
5.3 kΩ
Go to Step 21Go to Step 20
20Replace the EI system ignition coil.
Is the repair complete?–Go to Step 2–

ENGINE CONTROLS 1F–27
DAEWOO M-150 BL2
Engine Cranks But Will Not Run (Cont’d)
StepActionValue(s)YesNo
21
1. 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–
23
1. 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
24
1. Turn the ignition OFF.
2. Disconnect the electrical connector at the fuel
pump.
3. Connect a test light between the fuel pump
terminals 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 Step 32
25Replace the fuel pump.
Is the repair complete?–Go to Step 2–
26
Is the fuel pressure within the value specified?
380 kPa
(55 psi)
Go to Step 27Go to Step 29
27Check the fuel for contamination.
Is the fuel contaminated?–Go to Step 28Go to Step 41
28
1. Remove the contaminated fuel from the fuel tank.
2. Clean the fuel tank as needed.
Is the repair complete?
–
Go to Step 2
–
29
1. 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?
380 kPa
(55 psi)
Go to Step 2Go to Step 30
30
1. 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–
32
1. Remove the fuel pump assembly from the fuel
tank.
2. Inspect the fuel pump sender and the fuel
coupling hoses for a restriction.
3. Inspect the in-tank fuel filter for restriction.
Is the problem found?
–
Go to Step 33Go to Step 25

1F–38 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F050
MAIN RELAY CIRCUIT CHECK
Circuit Description
When the ignition is turned On or to the START position,
the main relay is energized. The main relay then supply
voltage to the engine fuse block fuse EF25 and EF26.
The Electronic Ignition (EI) system ignition coil is sup-
plied voltage through the engine fuse block fuse EF26.
The fuel injectors are supplied voltage through the en-
gine fuse block fuse EF25.Diagnostic Aids
An intermittent problem may be caused by a poor
connection, rubbed through wire insulation, or a bro-
ken wire inside the insulation.
A fault main relay will cause a no start condition.
There will be no voltage supplied to the EI system
ignition coil, or the fuel injectors. Without voltage sup-
plied to these components, they will not operate.

ENGINE CONTROLS 1F–45
DAEWOO M-150 BL2
IGNITION SYSTEM CHECK
Circuit Description
The Electronic Ignition (EI) system uses a waste spark
method of spark distribution. In this type of EI system,
the Crankshaft Position (CKP) sensor is mounted to the
oil pump near a slotted wheel that is a part of the crank-
shaft pulley. The CKP sensor sends reference pulses to
the Engine Control Module (ECM). The ECM then trig-gers the EI system ignition coil. Each cylinder is individu-
al with coil per cylinder in sequence.
This leaves the remainder of the high voltage to be used
to fire the spark plug in the cylinder on its compression
stroke. Since the CKP sensor is in a fixed position, tim-
ing adjustments are not possible or needed.
Ignition System Check
Caution: Use only electrically insulated pliers when
handling ignition wires with the engine running to
prevent an electrical shock.
StepActionValue(s)YesNo
1
1. Remove the spark plugs.
2. Inspect for wet spark plugs, cracks, wear,
improper gap, burned electrodes, or heavy
deposits.
3. Replace the spark plugs as needed.
Is the repair complete?
–
System OKGo to Step 2
2
Check for the presence of spark from all of the
ignition wires while cranking the engine.
Is spark present from all of the ignition wires?
–
System OKGo to Step 3
3
1. Measure the resistance of the ignition wires.
2. Replace any ignition wire(s) with a resistance
above the value specified.
3. Check for the presence of spark from all of the
ignition wires.
Is spark present from all of the ignition wires?
30000 ΩSystem OKGo to Step 4
4Is spark present from at least one of the ignition
wires, but not all of the ignition wires?Go to Step 5Go to Step 12
5
1. Turn the ignition OFF.
2. Disconnect the Electronic Ignition (EI) system
ignition coil connector.
3. While cranking the engine, measure the voltage
at the EI system ignition coil connector terminal 1.
Does the voltage fluctuate within the values
specified?
0.2–2.0 VGo to Step 8Go to Step 6
6
Check for an open in the wire from EI system
ignition coil connector terminal 1 to the Engine
Control Module (ECM) connector terminal 66.
Is the problem found?
–
Go to Step 7Go to Step 11
7
1. Repair the wiring as needed.
2. Connect the EI system ignition coil connector.
3. Check for the presence of spark from all of the
ignition wires.
Is spark present from all of the ignition wires?
–
System OK
–
8
While cranking the engine, measure the voltage at
the EI system ignition coil connector terminal 2.
Does the voltage fluctuate within the values
specified?
0.2–2.0 VGo to Step 10Go to Step 9

1F–46 ENGINE CONTROLS
DAEWOO M-150 BL2
Ignition System Check (Cont’d)
StepActionValue(s)YesNo
9
Check for an open in the wire from EI system
ignition coil connector terminal 2 to the Engine
Control Module (ECM) connector terminal 1.
Is the problem found?
–
Go to Step 7Go to Step 11
10
1. Replace the EI system ignition coil.
2. Connect the EI system ignition coil connector.
3. Check for the presence of spark from all of the
ignition wires.
Is spark present from all of the ignition wires?
–
System OK
–
11
1. Replace the ECM.
2. Connect the EI system ignition coil connector.
3. Check for the presence of spark from all of the
ignition wires.
Is spark present from all of the ignition wires?
–
System OK
–
12
1. Turn the ignition OFF.
2. Disconnect the crankshaft position (CKP) sensor
connector.
3. Measure the resistance between the CKP sensor
terminals 1 and 2.
Is the resistance within the value specified?
4. Measure the resistance between following
terminals.
Terminals 1 and 3 of CKP sensor.
Terminals 2 and 3 of CKP sensor.
Is the resistance within the value specified?
400–600 Ω
∞
Go to Step 14Go to Step 13
13Replace the crankshaft position sensor.
Is the repair complete?–System OK–
14
1. Turn the ignition ON.
2. Measure the voltage between the CKP sensor
connector terminals 1 and 3.
Is the voltage within the value specified?
0.95–1.10 VGo to Step 20Go to Step 15
15
Measure the voltage between the CKP sensor
connector terminal 1 and ground.
Is the voltage within the value specified?
0.95–1.10 VGo to Step 18Go to Step 16
16
Check the wire between the CKP sensor connector
terminal 1 and the ECM connector terminal 54 for an
open or short.
Is the problem found?
–
Go to Step 17Go to Step 10
17
Repair the wire between the CKP sensor connector
terminal 1 and the ECM connector terminal 54.
Is the repair complete?
–
System OK
–
18
Check the wire between the CKP sensor connector
terminal 3 and ground for an open or short.
Is the problem found?
–
Go to Step 19Go to Step 11
19
Repair the wire between the CKP sensor connector
terminal 3 and ground.
Is the repair complete?
–
System OK
–
20
1. Turn the ignition ON.
2. Measure the voltage between the CKP sensor
connector terminals 2 and 3.
Is the voltage within the value specified?
0.95–1.10 VGo to Step 24Go to Step 21

ENGINE CONTROLS 1F–47
DAEWOO M-150 BL2
Ignition System Check (Cont’d)
StepActionValue(s)YesNo
21
Measure the voltage between the CKP sensor
connector terminal 2 and ground.
Is the voltage within the value specified?
0.95–1.10 VGo to Step 18Go to Step 22
22
Check the wire between the CKP sensor connector
terminal 2 and the ECM connector terminal 24 for an
open or short.
Is the problem found?
–
Go to Step 23Go to Step 11
23
Repair the wire between the CKP sensor connector
terminal 2 and the ECM connector terminal 24.
Is the repair complete?
–
System OK
–
24
1. Turn the ignition OFF.
2. Connect a test light between the EI system
ignition coil connector terminal 2 and ground.
3. Turn the ignition ON.
Is the test light on?
–
Go to Step 27Go to Step 25
25
Check for an open in the wiring between the EI
system ignition coil connector, terminal 1 and the
main relay connector terminal 87.
Is the problem found?
–
Go to Step 26
Go to “Main
Relay Circuit
Check”
26
Repair the open in the wiring between the EI system
ignition coil connector terminal 1 and the main relay
connector terminal 87.
Is the repair complete?
–
System OK
–
27
Check for a damage in the terminal of the EI system
ignition coil connector and repair as needed.
Is the repair complete?
–
System OK
–

1F–48 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F090
ENGINE COOLING FAN CIRCUIT CHECK
Circuit Description
The engine cooling fan circuit operates the cooling fan.
The cooling fan is controlled by the engine control mod-
ule (ECM) based on input from the coolant temperature
sensor (CTS) and the A/C ON/OFF. The ECM controls
the low speed cooling fan operation by internally ground-
ing the ECM connector terminal 39. This energizes the
low speed cooling fan relay and operates the cooling fan
at low speed. The low speed cooling fan operation is
achieved by the cooling fan resistor causing a drop in
the voltage supplied to the cooling fan. The ECM con-
trols the high speed cooling fan operation by internally
grounding the ECM connector terminal 5. This ener-
gizes the high speed cooling fan relay, bypassing the ra-
diator fan resistor. This results in high speed cooling fan
operation.
Diagnostic Aids
If the owner complained of an overheating problem, it
must be determined if the complaint was due to anactual boil over, or the engine coolant temperature
gauge indicated overheating. If the engine is over-
heating and the cooling fans are on, the cooling sys-
tem should be checked.
If the engine fuse block fuse EF15 become open
(blown) immediately after installation, inspect for a
short to ground in the wiring of the appropriate circuit.
If the fuse become open (blown) when the cooling
fans are to be turned on by the Engine Control Mod-
ule (ECM), suspect a faulty cooling fan motor.
The ECM will turn the cooling fan on at low speed
when the coolant temperature is 93C (199F). The
ECM will turn the cooling fans off when the coolant
temperature is 90C (194F).
The ECM will turn the cooling fans on at high speed
when the coolant temperature is 100C (212F). The
ECM will change the cooling fans from high speed to
low speed when the coolant temperature is 97C
(207F).