Daewoo Nubira. Manual — part 112

1F – 30

I

ENGINE CONTROLS

DAEWOO V–121 BL4

On–Board Diagnostic (OBD II) System Check

Step

Action

Value(s)

Yes

No

1

1. Ignition ON, engine OFF.
2. Observe the malfunction indicator lamp (MIL)

Is the MIL on?

Go to Step 2

Go to ”No Mal-

function Indica-

tor Lamp”

2

1. Ignition OFF.
2. Install the scan tool.
3. Ignition ON.
4. Attempt to display the powertrain control mod-

ule (PCM)/engine control module (ECM) en-
gine data with the scan tool.

Does the scan tool display the PCM/ECM engine
data?

Go to Step 3

Go to Step 8

3

1. Using the scan tool output test function, select

MIL dash lamp control and command the MIL
OFF.

2. Observe the MIL.

Does the MIL turn OFF?

Go to Step 4

Go to ”Malfunc-

tion Indicator

Lamp on

Steady”

4

Attempt to start the engine.
Does the engine start and continue to run?

Go to Step 5

Go to ”Engine

Cranks But Will

Not Run”

5

Select DISPLAY DTC with the scan tool.
Are any Diagnostic Trouble Codes (DTCs) stored?

Go to Step 6

Go to Step 7

6

Check the display for DTCs P0107, P0108, P0113,
P0118, P0122, P0123, P0712, P1392.
Are two or more of the following DTCs stored?

Go to ”Multiple

PCM/ECM In-

formation Sen-

sor DTCs Set”

Go to applica-

ble DTC table

7

Compare the PCM/ECM data values displayed on
the scan tool to the typical engine scan data values.
Are the displayed values normal or close to the typi-
cal values?

Go to ”PCM/

ECM Output

Diagnosis”

Go to indicated

component

system check

8

1. Ignition OFF, disconnect the PCM/ECM.
2. Ignition ON, engine OFF.
3. Check the class 2 data circuit for an open,

short to ground, or short to voltage. Also,
check the Data Link Connector (DLC) ignition
feed circuit for an open or short to ground and
the DLC ground circuits for an open.

Is a problem found?

Go to Step 9

Go to Step 10

9

Repair the open, short to ground or short to voltage
in the class 2 data circuit or the DLC ignition feed cir-
cuit or DLC ground circuts.
Is the repair complete?

System OK

10

1. Attempt to reprogram the PCM/ECM.
2. Attempt to display the PCM/ECM data with the

scan tool.

Does the scan tool display PCM/ECM engine data?

Go to Step 2

Go to Step 11

11

Replace the PCM/ECM.
Is the repair complete?

System OK

ENGINE CONTROLS 1F – 31

DAEWOO V–121 BL4

PCM/ECM OUTPUT DIAGNOSIS

Circuit Description

The powertrain control module (PCM)/engine control
module (ECM) controls most components with electronic
switches which complete a ground circuit when turned on.
These switches are arranged in groups of 4 and 7, and are
called either a surface mounted quad driver module, which
can independently control up to 4 output terminals or an
Output Driver Module (ODM), which can independently
control up to 7 outputs. Not all of the outputs are always
used.

Drivers are fault protected. If a relay or solenoid is shorted,
having very low or zero resistance, or if the control side of
the circuit is shorted to voltage, it would allow too much
current flow into the PCM/ECM. The driver senses this
and the output is turned OFF or its internal resistance in-
creases to limit current flow and protect the PCM/ECM
and driver. The result is high output terminal voltage when
it should be low. If the circuit from B+ to the component or
the component is open, or the control side of the circuit is
shorted to ground, terminal voltage will be low. Either of
these conditions is considered to be a driver fault.

Drivers also have a fault line to indicate the presence of a
current fault to the PCM/ECM’s central processor. A scan
tool displays the status of the driver fault lines as 0=OK
and 1=Fault.

Diagnostic Aids

The scan tool has the ability to command certain compo-
nents and functions ON and OFF. If a component or func-
tion does not have this capability, operate the vehicle dur-
ing its normal function criteria to check for an open or
shorted circuit.

An open or short to ground will appear in the open posi-
tions on the scan tool only when it is not commanded by
the PCM/ECM or the scan tool, while a short to voltage will
appear in the short positions on the scan tool only while the
component is being commanded by the PCM/ECM or
scan tool.

Test Description

Number(s) below refer to the step number(s) on the Diag-
nostic Table.

1.

The Powertrain On–Board Diagnostic (OBD II) 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.

2.

A 1 in any of the positions indicates that an open or
short is present in the corresponding circuit for that
position.

4.

An open or short to ground will appear in the open
positions on the scan tool only when it is not com-
manded by the PCM/ECM or scan tool, while a
short to voltage will appear in the short positions on
the scan tool only while the component is being
commanded by the PCM/ECM or scan tool.

5.

Proper operation of any component of function with
no 1 in any operation of the positions indicates that
system operation is normal at this time.

6.

A component or function that failed to operate at
this point indicates that the fault is not on the PCM/
ECM side of the circuitry.

8.

The 1 going away after disconnecting the compo-
nent electrical connector indicates that the compo-
nent or component side wiring is at fault. If the scan
tool indicates a fault after disconnecting the compo-
nent electrical connector and verifying that no open
or short is present in the circuit, then the PCM/ECM
is faulty.

9.

The replacement PCM/ECM must be repro-
grammed. Refer to the latest Techline procedure for
PCM/ECM reprogramming.

10. If no faults have been found at this point, refer to

”Diagnostic Aids” in this section for additional
checks and information.

1F – 32

I

ENGINE CONTROLS

DAEWOO V–121 BL4

PCM/ECM Output Diagnosis

Step

Action

Value(s)

Yes

No

1

Perform an On–Board Diagnostic (OBD II) System
Check.
Is the check performed ?

Go to Step 2

Go to ”On–

Board Diagnos-

tic System

Check”

2

Install the scan tool.
Is there a number 1 below any of the numbered posi-
tions in the OUTPUT DRIVERS?

Go to Step 3

Go to Step 4

3

Check for an open or shorted circuit in any corre-
sponding position (circuit) that contained a number
1 and repair as necessary.
Is a repair necessary?

Go to Step 10

Go to Step 8

4

Command the output being checked with a scan tool
while watching the corresponding position for each
circuit.
Do any of the positions change to a 1?

Go to Step 7

Go to Step 5

5

Command the output being checked with a scan tool
while watching the corresponding position for each
circuit.
Does the component or function operate when com-
manded?

Go to Step 10

Go to the ap-

propriate com-

ponent repair

6

Repair the short to voltage in the corresponding cir-
cuit for position (circuit) that displayed a 1.
Is the repair complete?

Go to Step 10

7

Disconnect the electrical connector to the compo-
nent connected to the faulty circuit.
Is a 1 still displayed in the corresponding OUTPUT
DRIVER position?

Go to Step 9

Go to the ap-

propriate com-

ponent repair

8

Replace the powertrain control module (PCM)/en-
gine control module (ECM)
Is the repair complete?

Go to Step 10

9

Operate the vehicle within the conditions under
which the original symptom was noted.
Does the system now operate properly?

System OK

Go to Step 2

ENGINE CONTROLS 1F – 33

DAEWOO V–121 BL4

MULTIPLE PCM/ECM INFORMATION SENSOR DTCS SET

Circuit Description

The powertrain control module (PCM)/engine control
module (ECM) monitors various sensors to determine en-
gine operating conditions. The PCM/ECM controls fuel de-
livery, spark advance, transaxle operation, and emission
control device operation based on the sensor inputs.

The PCM/ECM provides a sensor ground to all of the sen-
sors. The PCM/ECM applies 5 volts through a pullup resis-
tor 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 Tem-
perature (IAT) sensor, and the Transmission Fluid Tem-
perature (TFT) sensor. The PCM/ECM provides the Ex-
haust Gas Recirculation (EGR) Pintle Position Sensor, the
Throttle Position (TP) sensor, the Manifold Absolute Pres-
sure (MAP) sensor, the Air Conditioning Temperature
(ACT) sensor and the Fuel Tank Pressure Sensor with a
5 volt reference and a sensor ground signal. The PCM/
ECM monitors the separate feedback signals from these
sensors to determine their operating status.

Diagnostic Aids

Be sure to inspect PCM/ECM and 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 Diagnostic Trouble Codes
(DTCs) to be set: P0108, P0113, P0118, P0123, P1106,
P1111, P1115, P1121, P1625.

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 PCM/
ECM and the splice will cause one or more of the following
DTCs to be set: P0108, P0113, P0118, P0123, P1106,
P1111, P1115, P1121.

A short to ground in the 5 volt reference circuit or an open
in the 5 volt reference circuit between the PCM/ECM and
the splice will cause one or more of the following DTCs to
be set: P0107, P0112, P0117, P0122, P1107, P1112,
P1114, P1122.

Check for the following conditions:

S

Inspect for a poor connection at the PCM/ECM.
Inspect harness connectors for backed–out termi-
nals, improper mating, broken locks, improperly
formed or damaged terminals, and poor terminal–
to–wire connection.

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 (OBD II) 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 PCM/ECM must be repro-

grammed. Refer to the latest Techline procedure for
PCM/ECM reprogramming.