Daewoo Matiz (2003 year). Manual - part 49

1F – 106 ENGINE CONTROLS

DIAGNOSTIC TROUBLE CODE (DTC) – P0171 FUEL TRIM SYSTEM TOO LEAN

System Description

To provide the best possible combination of driveability,
fuel economy, and emission control, a Closed Loop air/
fuel metering system is used. While in Closed Loop, the
Engine Control Module (ECM) monitors the oxygen sen-
sor (O2S) signal voltage and adjusts fuel delivery based
on signal voltage. A change made to fuel delivery will be
indicated by the long and short term fuel trim values
which can be monitored with the scan tool. Ideal fuel trim
values are around 128 (0%). If the O2S signal is indicat-
ing a lean condition, the ECM will add fuel resulting in
fuel trim values above 128 (0% to 100%). If a rich condi-
tion is detected, the fuel trim values will be below 128
(0% to –100%), indicating that the ECM is reducing the
amount of fuel delivered. If exhaust emissions reach an
excessive level due to a lean or rich condition, a fuel trim
Diagnostic Trouble Code (DTC) is set.

Conditions for Setting the DTC

No intrusive tests active.

DTCs P0106, P0107, P0108, P0112, P0113, P0117,
P0118, P0122, P0123, P0125, P0131, P0132,
P0133, P0134, P0137, P0138, P0140, P0141,
P1167, P1171, P0201, P0202, P0203, P0204,
P0300, P0336, P0337, P0341, P0342, P0402,
P0404, P1404, P0405, P0406, P0443, P0506, and
P0507are not set.

The average of short term fuel trim value is greater
than or equal to 120.

Throttle Position (TP) is less than 95%.

Engine speed is between 700 and 6000 rpm.

Barometric Pressure (BARO) is greater than 92.0
kPa (10.4 psi).

Coolant temperature is between 80

C (176

F) and

115

C (239

F).

Manifold Absolute Pressure (MAP) is more than 90
kPa (10.2 psi).

System is in closed loop.

Adaptive index is ready.

Action Taken when the DTC Sets

Emission related.

“Armed” after two trip with a fail.

“Disarmed” after one trip with a pass.

MIL on if failure is detected in three consecutive trips.

Stores a History DTC on the third consecutive 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).

Conditions for Clearing the MIL/DTC

The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.

A history DTC will clear after 40 consecutive warm up
cycles without a fault.

DTC(s) can be cleared by using the scan tool.

Diagnostic Aids

Important: After repairs, use the scan tool Fuel Trim
Reset function to reset the long-term fuel trim to 128
(0%).

Fuel pressure – The system will be lean if the pres-
sure is too low. It may be necessary to monitor fuel
pressure while driving the vehicle at various road
speeds and/or loads to confirm.

Map sensor – An output that causes the ECM to
sense a lower than normal manifold pressure (high
vacuum) can cause the system to go lean. Discon-
necting the MAP sensor will allow the ECM to substi-
tute a fixed (default) value for the MAP sensor. If the
lean condition is gone when the sensor is discon-
nected, substitute a known good sensor and recheck.

Fuel contamination – Water, in even small amounts,
near the in-tank fuel pump inlet can be delivered to
the injector. The water causes a lean exhaust and
can set DTC P0171.

Check for poor O2S or MAP sensor connection at the
ECM. Inspect the harness connectors for the following
conditions:

Backed-out terminals

Improper mating

Broken locks

Improperly formed

Damaged terminals

Poor terminal-to-wire connection

Inspect the wiring harness for damage. If the harness
appears to be OK, observe the O2S display on the scan
tool while moving the connectors and the wiring harness
related to the engine harness. A change in the display
will indicate the location of the fault.

Check the brake power booster check valve for possible
leaks.

ENGINE CONTROLS 1F – 107

DTC P0171 – Fuel Trim System Too Lean

Step

Action

Value(s)

Yes

Perform an Euro On-Board Diagnostic (EOBD)
System Check.
Is the system check complete?

–

Go to Step 2

Go to

“On-Board
Diagnostic

System Check”

1. Install the scan tool to the Data Link Connector

(DLC).

2. Turn the ignition ON.
Are any component related Diagnostic Trouble
Codes (DTCs) set?

–

Go to

Applicable DTC

table

Go to Step 3

With the engine running, operate the vehicle until the
LOOP STATUS indicates closed.
Is the Long Term Fuel Trim value below the
specified value?

–22%

Go to Step 4

Go to Step 5

1. Turn the ignition switch 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 The DTC as
noted.

Does the Long Term Fuel Trim value go below the
specified value while operating under the specified
conditions?

–22%

Go to Step 16

Go to Step 5

Visually/physically check the following items:

Vacuum hoses for splits, kinks and improper
connections.

Crankcase ventilation oil/air separator for proper
installation.

Exhaust system for corrosion, leaks, loose or
missing hardware.

Oxygen sensor (O2S) is installed securely and
the pigtail harness is not contacting exhaust
manifold or engine.

Fuel for excessive water, alcohol, or other
contaminants.

Engine Control Module (ECM) and sensor
grounds are clean, tight, and in their proper
locations.

Do any of the above checks isolate a condition
requiring repair?

–

Go to Step 7

Go to Step 6

1. Disconnect the Manifold Absolute Pressure

(MAP) sensor electrical connector.

2. Operate the vehicle in Closed Loop while

monitoring the Long Term Fuel Trim value.

Is the Long Term Fuel Trim value below the
specified value?

–22%

Go to Step 15

Go to Step 9

1. Repair the malfunction found in Step 5.
2. Recheck the Long Term Fuel Trim value while

operating the engine.

Is the Long Term Fuel Trim value below the
specified value?

–22%

Go to Step 8

Go to Step 9

Lean condition is not present.
Does a driveability problem exist?

–

Go to

“Symptom

Diagnosis”

Go to Step 16

1F – 108 ENGINE CONTROLS

DTC P0171 – Fuel Trim System Too Lean (Cont’d)

Step

Action

Value(s)

Yes

1. Visually/physically inspect the following items for

vacuum leaks:

Intake manifold.

Throttle body.

Injector O-rings.

2. Repair any leaks found as necessary.
Is the repair complete?

–

Go to Step 16

Allow the engine to idle.
Are the Idle Air Control (IAC) counts above the
specified value?

Go to Step 11

Go to Step 12

Check the fuel for excessive water, alcohol, or other
contaminants and correct the contaminated fuel
condition if present.
Is the repair complete?

–

Go to Step 16

Go to Step 13

Check the IAC valve performance. Refer to “DTC
P0506 Idle Speed RPM Lower Than Desired Idle
Speed” or “DTC P0507 Idle Speed RPM Higher
Than Desired Idle Speed” in this section and repair
as necessary.
Is the repair complete?

–

Go to Step 16

Go to Step 13

1. Connect a fuel pressure gauge to the fuel system.
2. Turn the ignition OFF for at least 10 seconds.
3. Turn the ignition ON, with the engine OFF. The

fuel pump will run for approximately 2–3 seconds.
It may be necessary to cycle the ignition switch
ON more than once to obtain maximum fuel
pressure.

4. Note the fuel pressure with the fuel pump running.

The pressure should be within the specified value.
When the fuel pump stops, the pressure may vary
slightly then hold steady.

Is the fuel pressure steady and does the fuel
pressure hold?

380 KPa

(55 psi)

Go to Step 14

Go to

“Fuel System

Diagnosis”

1. Start and idle the engine at normal operating

temperature.

2. The fuel pressure noted in the above step should

drop by the indicated value.

Does the fuel pressure drop by the indicated value?

21–69 KPa

(3–10 psi)

Go to

“Fuel Injector

2alance Test”

Go to

“Fuel System

Diagnosis”

Replace the MAP sensor.
Is the action complete?

–

Go to Step 16

–

1. 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 this DTC as specified in the supporting
text.

Does the scan tool indicate that this diagnostic has
run and passed?

–

Go to Step 17

Go to Step 2

Check if any additional DTCs are set.
Are any DTCs displayed that have not been
diagnosed?

–

Go to

applicable DTC

table

System OK

ENGINE CONTROLS 1F – 109

DIAGNOSTIC TROUBLE CODE (DTC) – P0172 FUEL TRIM SYSTEM TOO RICH

System Description

Conditions for Setting the DTC

No intrusive tests active.

DTCs P0106, P0107, P0108, P0112, P0113, P0117,
P0118, P0122, P0123, P0131, P0132, P0133,
P0134, P0137, P0138, P1167, P1171, P0300,
P0336, P0337, P0341, P0342, P0402, P0404,
P1404, P0405, P0406, P0443, P0506, and P0507are
not set.

The average of short term fuel trim value is greater
than or equal to 120.

Throttle Position (TP) is less than 95%.

Engine speed is between 700 and 6000 rpm.

Barometric Pressure (BARO) is greater than 90.0
kPa (10.4 psi).

Coolant temperature is between 80

C (176

F) and

115

C (239

F).

Manifold Absolute Pressure (MAP) is more than 70
kPa (10.2 psi).

System is in closed loop.

Adaptive index is ready.

Action Taken when the DTC Sets

Emission related.

“Armed” after two trip with a fail.

“Disarmed” after one trip with a pass.

MIL on if failure is detected in three consecutive trips.

Stores a History DTC on the third consecutive 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).

Conditions for Clearing the MIL/DTC

The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.

A history DTC will clear after 40 consecutive warm up
cycles without a fault.

DTC(s) can be cleared by using the scan tool.

Diagnostic Aids

Important: After repairs, use the scan tool Fuel Trim
Reset function to reset the long-term fuel trim to 128
(0%).

Check for poor connection at the ECM. Inspect the har-
ness connectors for the following conditions:

Backed-out terminals.

Improper mating.

Broken locks.

Improperly formed.

Damaged terminals.

Poor terminal-to-wire connection.

If a DTC P1404 is also set, check the 5 volt reference
circuits for a short to voltage.

Check for a restricted exhaust system.

A shorted 5 volt reference circuit may cause a DTC
P0172 to set. Check the 5 volt reference sensors for ab-
normal readings.

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