2004 DAEWOO LACETTI Service Repair Manual

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Page 345 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 99
DAEWOO V–121 BL4

Page 346 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 100IENGINE CONTROLS
DAEWOO V–121 BL4
ENGINE COOLING FAN CIRCUIT CHECK – DUAL FAN
(1.8L DOHC)
Circuit Description
The engine cooling fan circuit operates the main cooling
fan and the auxilia

1F – 100IENGINE CONTROLS
DAEWOO V–121 BL4
ENGINE COOLING FAN CIRCUIT CHECK – DUAL FAN
(1.8L DOHC)
Circuit Description
The engine cooling fan circuit operates the main cooling
fan and the auxiliary cooling fan. The cooling fans are con-
trolled by the engine control module (ECM) based on in-
puts from the Engine Coolant Temperature (ECT) sensor
and the Air Conditioning Pressure (ACP) sensor. The
ECM controls the low speed cooling fan operation by inter-
nally grounding the ECM connector terminal K28. This en-
ergizes the low speed cooling fan relay and operates the
main cooling fan and the auxiliary cooling fan at low speed
as the cooling fans are connected in a series circuit. The
ECM controls the high speed cooling fan operation by in-
ternally grounding the ECM connector terminal K28 and
the ECM connector terminal K12 at the same time. This
energizes the low speed cooling fan relay, the high speed
cooling fan relay, and the series/parallel cooling fan relay
resulting in high speed fan operation as the cooling fans
are now connected in a parallel circuit.
Diagnostic Aids
S If the owner complained of an overheating problem,
it must be determined if the complaint was due to
an actual boil over, or the engine coolant tempera-
ture gauge indicated overheating. If the engine is
overheating and the cooling fans are on, the cooling
system should be checked.
S If the engine fuse block fuses Ef21, Ef6, Ef8 be-
come open (blown) immediately after installation,
inspect for a short to ground in the wiring of the ap-
propriate circuit. If the fuses become open (blown)
when the cooling fans are to be turned on by the
ECM, suspect a faulty cooling fan motor.
S The ECM will turn the cooling fans on at low speed
when the coolant temperature is 97°C (207°F). The
ECM will turn the cooling fans off when the coolant
temperature is 94°C(201°F).
S The ECM will turn the cooling fans on at high speed
when the coolant temperature is 101°C (214°F).
The ECM will change the cooling fans from high
speed to low speed when the coolant temperature
is 98°C (208°F).S The ECM will turn the cooling fans on at low speed
when the A/C system is on. The ECM will change
the cooling fans from low speed to high speed
when the high side A/C pressure is 1882 kPa (273
psi) then return to low speed when the high side
A/C pressure is 1448 kPa (210 psi). When the A/C
system is on, the ECM will change the cooling fans
from low to high speed when the coolant tempera-
ture reaches 117°C (244°F) then return to low
speed when the coolant temperature reaches
11 4°C (237°F).
S The cooling fan circuit can be checked quickly by
disconnecting the ECM connector 2 and grounding
the connector terminal K28. This should create low
speed cooling fan operation with the ignition ON. By
grounding the ECM connector terminals K28 and
K12 and turning the ignition ON, high speed cooling
fan operation should be achieved.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
4. This step, along with step 5, checks for the ability of
the ECM to operate the cooling fans.
8. This step, along with step 9, checks for the ability of
the ECM to operate the cooling fans in response to
A/C pressure readings.
16. After confirming battery voltage and the ECM sup-
plying a ground to the coil side of the cooling fan
relay A, by jumpering connector terminals 30 and
87 it will be determined if the relay is at fault or a
wiring problem is present.
31. This step checks for the presence of battery volt-
age to the main cooling fan when the A/C is on. If
battery voltage is present and the cooling fans are
not operating, the problem is in the ground side of
the cooling fan circuit.
37. By directly grounding the ECM connector terminals
K28 and K12, the main and auxiliary cooling fans
should run at high speed.
Engine Cooling Fan Circuit Check – Dual Fan (1.8L DOHC)
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) system
check.
Is the check completed?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Check the I/P fuse block fuse F2.
2. Replace the fuse as needed.
Is the fuse OK?–Go to Step 3Go to
”Diagnostic
Aids”

Page 347 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 101
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
31. Check the engine fuse block fuse Ef21, Ef6,
Ef8.
2. Replace the fuse as needed.
Is the fuse OK?–Go to Step 4Go to
”D

Page 348 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 102IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
111. Turn the ignition OFF.
2. Connect a scan tool to the DLC.
3. The coolant temperature should be above
97°C (207°C).
4.

1F – 102IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
111. Turn the ignition OFF.
2. Connect a scan tool to the DLC.
3. The coolant temperature should be above
97°C (207°C).
4. Disconnect the main cooling fan connector.
5. Connect a test light between the main cooling
fan connector terminal 1 and ground.
Is the test light on?–Go to Step 28Go to Step 17
121. Turn the ignition OFF.
2. Disconnect the cooling fan relay Low.
3. Connect a test light between the cooling fan
relay Low connector terminal 85 and ground.
4. Turn the ignition ON.
Is the test light on?–Go to Step 13Go to Step 24
131. Turn the ignition OFF.
2. Connect the cooling fan relay Low.
3. Disconnect engine control module (ECM) white
connector.
4. Connect a fused jumper between the ECM
connector terminal K28 and ground.
5. Turn the ignition ON.
Do the cooling fans run at low speed?–Go to Step 30Go to Step 14
14Check for an open wire between the low speed cool-
ing fan relay connector terminal 85 and the ECM
connector terminal K28.
Is the problem found?–Go to Step 25Go to Step 15
151. Turn the ignition OFF.
2. Disconnect the cooling fan relay Low.
3. Connect a test light between the cooling fan
relay Low connector terminal 30 and ground.
Is the test light on?–Go to Step 16Go to Step 23
16Connect a fused jumper between the cooling fan
relay Low connector terminals 30 and 87.
Do the cooling fans run at low speed?–Go to Step 26Go to Step 17
171. Disconnect the cooling fan control relay.
2. Connect a fused jumper between the cooling
fan relay Low connector terminals 30 and 87.
3. Connect a fused jumper between the cooling
fan control relay connector terminals 30 and
87.
Do the cooling fans run at low speed?–Go to Step 27Go to Step 18
18Check the wire between the cooling fan relay Low
connector terminal 87 to the main cooling fan con-
nector terminal 2 for an open.
Is the problem found?–Go to Step 22Go to Step 19
19Check the wire between the main cooling fan con-
nector terminal 1 and the cooling fan control relay
connector terminal 30 for an open.
Is the problem found?–Go to Step 22Go to Step 20

Page 349 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 103
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
20Check the wire between the cooling fan control relay
connector terminal 87A and the auxiliary cooling fan
connector terminal

Page 350 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 104IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
341. Turn the ignition OFF.
2. Connect a test light between the cooling fan
relay Hi connector terminal 30 and ground.
Is the

Page 351 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 105
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
411. Connect the cooling fan control relay.
2. Connect a fused jumper between the ECM
connector terminal K12 and ground.
3.

Page 352 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 106IENGINE CONTROLS
DAEWOO V–121 BL4
DATA LINK CONNECTOR DIAGNOSIS (1.4L/1.6L DOHC)
Circuit Description
The provision for communicating with the Engine Control
Module (ECM) is the Data Link C

1F – 106IENGINE CONTROLS
DAEWOO V–121 BL4
DATA LINK CONNECTOR DIAGNOSIS (1.4L/1.6L DOHC)
Circuit Description
The provision for communicating with the Engine Control
Module (ECM) is the Data Link Connector (DLC). It is lo-
cated under the instrument panel. The DLC is used to con-
nect the scan tool. Battery power and ground is supplied
for the scan tool through the DLC. The Keyword 2000 seri-
al data circuit to the DLC allows the ECM to communicate
with the scan tool. A Universal Asynchronous Receiver
Transmitter (UART) serial data line is used to communi-
cate with the other modules such as the Electronic Brake
Control Module (EBCM), the Supplemental Inflatable Re-
straint (SIR) system. and the Instrument Panel Cluster.
Diagnostic Aids
Ensure that the correct application (model line, car year,
etc.) has been selected on the scan tool. If communication
still cannot be established, try the scan tool on another ve-
hicle to ensure that the scan tool or cables are not the
cause of the condition.
An intermittent may be caused by a poor connection,
rubbed through wire insulation, or a broken wire inside the
insulation.
Any circuitry that is suspected of causing an intermittent
complaint should be thoroughly checked for the following
conditions:
S Backed–out terminals.S Improper mating of terminals.
S Broken locks.
S Improperly formed or damaged terminals.
S Poor terminal–to–wiring connection.
S Physical damage to the wiring harness.
S Corrosion.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic Table.
1. The On–Board Diagnostic (EOBD) System Check
prompts the technician to complete some basic
checks and store the freeze frame and failure re-
cords data on the scan tool if applicable. This
creates an electronic copy of the data taken when
the malfunction occurred. The information is then
stored on the scan tool for later reference.
2. Unlike the UART serial data circuit, the only time a
Class II serial data circuit has any voltage on it is
when a scan tool asks the ECM for information and
sends the information out.
5. Locate and repair any shorts that may have caused
the fuse to open before replacement, if the no volt-
age condition was due to an open fuse.
10. The scan tool or associated cables could be mal-
functioning. Refer to the scan tool’s manual for re-
pair information.

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