2004 DAEWOO LACETTI Service Repair Manual

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Page 497 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 251
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0481
HIGH SPEED COOLING FAN RELAY CIRCUIT FAULT
(1.4L DOHC)
Circuit Description
Ignition voltage is supplied directly to

ENGINE CONTROLS 1F – 251
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0481
HIGH SPEED COOLING FAN RELAY CIRCUIT FAULT
(1.4L DOHC)
Circuit Description
Ignition voltage is supplied directly to the cooling fan relay
coil. The engine control module(ECM) controls the relay
by grounding the control circuit via an internal switch called
a driver. The primary function of the driver is supply the
ground for the component being controlled. Each driver
has a fault line which is monitored by the ECM. When the
ECM is commanding a component ON, the voltage of the
control circuit should be low (near 0volts). When the ECM
is commanding the control circuit to a component OFF, the
voltage potential of the circuit should be high(near battery
voltage). If the fault detection circuit senses a voltage oth-
er than what is expected, the fault line status will change
causing the DTC to set.
The relay is used to control the high current flow to the
cooling fan motors. This allows the ECM driver to only
have to handle the relatively low current used by the relay.
Conditions for Setting the DTC
S The high speed cooling fan control circuit is an
open or a short to battery or a short to ground con-
dition exist.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will not illumi-
nate after three consecutive trip with a fail.S The ECM will record operating conditions ant the
time the diagnostic fail. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after four 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
Using Freeze Frame and/or failure records data may aid
in locating an intermittent condition. If the DTC cannot be
duplicated, the information included in the Freeze Frame
and/or failure records data can be useful in determining
how many miles since the DTC set. The fail counter and
Pass Counter can also be used to determine how many
ignition cycles the diagnostics reported a Freeze Frame
conditions (rpm, load, vehicle speed, temperature, etc.)
that .are noted. This will isolate when the DTC failed.
DTC P0481 – High Speed Cooling Fan Relay Circuit Fault
(1.4L DOHC)
StepActionValue(s)YesNo
1Perform an Euro On–Board Diagnostic (EOBD)
System Check.
Is the system check complete?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Turn the ignition switch to ON with the engine
OFF.
2. Install a scan tool.
3. Command the relay ON and OFF.
Does the relay turn ON and OFF when command-
ed?–Go to Step 3Go to Step 5
31. Turn the ignition switch to LOCK.
2. Disconnect the engine control module (ECM)
connector.
3. Turn the ignition switch to ON.
4. Using a digital voltmeter(DVM), measure the
current in high speed relay control circuit, at
terminal 9 to ground for 2 minutes.
Does the amperage measure less than the specified
value?0.75 ampsGo to
”Diagnostic
Aids”Go to Step 6

Page 498 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 252IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
41. Turn the ignition switch to LOCK.
2. Disconnect the relay.
3. Using a DVM, measure the resistance between
terminals 85 a

1F – 252IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
41. Turn the ignition switch to LOCK.
2. Disconnect the relay.
3. Using a DVM, measure the resistance between
terminals 85 and 9 in the relay control circuit in
the ECM harness connector to ground.
Does the DVM display infinite resistance?–Go to Step 12Go to Step 10
51. Turn the ignition switch to LOCK.
2. Disconnect the relay.
3. Connect a test light between the relay coil ter-
minals 86 and 85 in the relay harness connec-
tor.
4. Turn the Turn the ignition switch to ON.
5. Using the scan tool, command the relay ON
and OFF.
Does the test light turn ON and OFF with each com-
manded?–Go to Step 8Go to Step 6
6With the test light connected to ground, probe the
ignition feed circuit in the relay harness connector.
Does the test light illuminate?–Go to Step 7Go to Step 11
71. Turn the ignition switch to LOCK.
2. Reconnect the relay.
3. Disconnect the ECM connector containing the
relay control circuit.
4. Turn the Turn the ignition switch to ON.
5. With a fused jumper wire connected to ground,
probe the relay control circuit at terminal 9 in
the ECM harness connector.
Does the relay operate?–Go to Step 9Go to Step 10
8Check the connections at the relay.
Is a problem found and corrected?–Go to Step 14Go to Step 12
9Check the connection at the ECM.
Is a problem found and corrected?–Go to Step 11Go to Step 13
10Repair the faulty relay control circuit.
Is the repair complete?–Go to Step 14–
11Repair the faulty relay ignition feed circuit.
Is the repair complete?–Go to Step 14–
12Replace the relay.
Is the replacement complete?–Go to Step 14–
13Replace the ECM.
Is the replacement complete?–Go to Step 14–
141. 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 DTC as specifiec in the supporting
text.
Does the scan tool indicate that this diagnostic ran
and passed?–Go to Step 15Go to Step 2
15Check if any additional DTCs are set.
Are any DTCs displayed that have not been diag-
nosed?–Go to
Applicable DTC
tableSystem OK

Page 499 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 253
DAEWOO V–121 BL4

Page 500 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 254IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0481
HIGH SPEED COOLING FAN RELAY CIRCUIT FAULT
(1.6L DOHC)
Circuit Description
Ignition voltage is supplied directly to t

1F – 254IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0481
HIGH SPEED COOLING FAN RELAY CIRCUIT FAULT
(1.6L DOHC)
Circuit Description
Ignition voltage is supplied directly to the cooling fan relay
coil. The engine control module(ECM) controls the relay
by grounding the control circuit via an internal switch called
a driver. The primary function of the driver is supply the
ground for the component being controlled. Each driver
has a fault line which is monitored by the ECM. When the
ECM is commanding a component ON, the voltage of the
control circuit should be low (near 0volts). When the ECM
is commanding the control circuit to a component OFF, the
voltage potential of the circuit should be high(near battery
voltage). If the fault detection circuit senses a voltage oth-
er than what is expected, the fault line status will change
causing the DTC to set.
The relay is used to control the high current flow to the
cooling fan motors. This allows the ECM driver to only
have to handle the relatively low current used by the relay.
Conditions for Setting the DTC
S The high speed cooling fan control circuit is an
open or a short to battery or a short to ground con-
dition exist.
Action Taken When the DTC SetsS The Malfunction Indicator Lamp (MIL) will not illumi-
nate.
S The ECM will store conditions which were present
when the DTC was set as Failure Records data
only.
S This information will not be stored in the Freeze
Frame data.
Conditions for Clearing the MIL/DTC
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 more than
10 seconds.
Diagnostic Aids
Using Freeze Frame and/or failure records data may aid
in locating an intermittent condition. If the DTC cannot be
duplicated, the information included in the Freeze Frame
and/or failure records data can be useful in determining
how many miles since the DTC set. The fail counter and
Pass Counter can also be used to determine how many
ignition cycles the diagnostics reported a Freeze Frame
conditions (rpm, load, vehicle speed, temperature, etc.)
that .are noted. This will isolate when the DTC failed.
DTC P0481 – High Speed Cooling Fan Relay Circuit Fault
(1.6L DOHC)
StepActionValue(s)YesNo
1Perform an Euro On–Board Diagnostic (EOBD)
System Check.
Is the system check complete?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Turn the ignition switch to ON with the engine
OFF.
2. Install a scan tool.
3. Command the relay ON and OFF.
Does the relay turn ON and OFF when command-
ed?–Go to Step 3Go to Step 5
31. Turn the ignition switch to LOCK.
2. Disconnect the engine control module (ECM)
connector.
3. Turn the ignition switch to ON.
4. Using a digital voltmeter(DVM), measure the
current in high speed relay control circuit, at
terminal 9 to ground for 2 minutes.
Does the amperage measure less than the specified
value?0.75 ampsGo to
”Diagnostic
Aids”Go to Step 6

Page 501 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 255
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
41. Turn the ignition switch to LOCK.
2. Disconnect the relay.
3. Using a DVM, measure the resistance between
terminals 85

Page 502 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 256IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
141. Using the scan tool, clear the Diagnostic
Trouble Codes (DTCs).
2. Start the engine and idle at normal operating
tempera

Page 503 of 2643

DAEWOO LACETTI 2004 Service Repair Manual ENGINE CONTROLS 1F – 257
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0501
VEHICLE SPEED NO SIGNAL (M/T ONLY)
Circuit Description
Vehicle speed information is provided to the engine control
mo

Page 504 of 2643

DAEWOO LACETTI 2004 Service Repair Manual 1F – 258IENGINE CONTROLS
DAEWOO V–121 BL4
S Damaged terminals
S Poor terminal to wire connection
S Physical damage to the wiring harness
Ensure the VSS is correctly torqued to the trnasaxle hous

1F – 258IENGINE CONTROLS
DAEWOO V–121 BL4
S Damaged terminals
S Poor terminal to wire connection
S Physical damage to the wiring harness
Ensure the VSS is correctly torqued to the trnasaxle hous-ing.
Refer to ”Intermittents” in this section.
DTC P0501 – Vehicle Speed No Signal (M/T Only)
StepActionValue(s)YesNo
1Perform an Euro On–Board Diagnostic (EOBD)
System Check.
Is the system check complete?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
2Notice : Running the vehicle in gear with the wheels
hanging down at full travel will damage the drive
axles.
1. Turn the ignition ON, with the engine OFF.
2. Install a scan tool.
3. Raise the drive wheels.
4. Support the lower control arms so that the
drive axles are in a horizontal (straight) posi-
tion.
5. Allow the engine to idle in gear.
Does the scan tool display vehicle speed above the
specified value?0 mphGo to Step 3Go to Step 4
31. Turn the ignition ON, with the engine OFF.
2. Review the Freeze Frame data and note the
parameters.
3. Operate the vehicle within the Freeze Frame
conditions and Conditions for Setting this DTC.
Does the scan tool display the vehicle speed above
the specified value?0 mphGo to Step 12Go to Step 4
41. Turn the ignition OFF.
2. Disconnect the engine control module(ECM)
connector 51.
3. Using a digital voltmeter(DVM) connected to
ground, measure the voltage in the Vehicle
Speed Sensor (VSS) signal circuit, at terminal
C while rotating the wheels.
Is the voltage greater than or eqaul to specified val-
ue?0.5VGo to Step 12Go to Step 5
5Measure the resistant in the VSS signal circuit while
rotating the wheels.
Is the resistance greater than the specified value?1950WGo to Step 6Go to Step 7
6Check the VSS signal circuit for an open and repair
as necessary.
Is the repair complete?–Go to Step 12Go to Step 9
7Is the resistance value within or equal to the speci-
fied value?1300–1950WGo to Step 8Go to Step 9
8Check the VSS signal circuit for a short to ground or
for being shorted together and repair as necessary.
Is a repair necessary?–Go to Step 12Go to Step 12
91. Remove the VSS.
2. Measure the resistance between terminals A
and C.
Is the resistance value within the specified value?1300–1950WGo to Step 11Go to Step 10

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