SsangYong Musso. Manual - part 161

1F-228 ENGINE CONTROLS

SSANGYONG Y158

DIAGNOSTIC TROUBLE CODE (DTC) P0171

BANK 1 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 heated
oxygen sensor (O2S 1) 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 1 (0 %). If the O2S 1
signal is indicating a lean condition, the ECM will add
fuel resulting in fuel trim values above 1 (0 % to 100 %).
If a rich condition is detected, the fuel trim values will
be below 1 (0 % to -100 %), indicating that the ECM is
re- ducing the amount of fuel delivered.

If exhaust emissions reach an excessive level due to a
lean condition, a fuel trim Diagnostic Trouble Code (DTC)
P0171.

Conditions for Setting the DTC

Short Term Trim

•••••

DTCs P0101, P0102, P0103, P0171, P0172, P0444
and P0445 are not set.

•••••

Short term trim at lean limit is equal to 65 % (2.3L
DOHC).

•••••

Short term trim at lean limit is less than or equal to
75 % (3.2L DOHC).

Short Term Adaption

•••••

DTCs P0101, P0102, P0103, P0171, P0172, P0335
and P0336 are not set.

•••••

Short term adaption exceeds lean threshold is less
than or equal to 80 % (2.3L DOHC).

•••••

Short term adaption exceeds lean threshold is less
than or equal to 78 % (3.2L DOHC).

Long Term Adaption

•••••

DTCs P0101, P0102, P0103, P0111, P0112, P0113,
P0116, P0117, P0118, P0125, P0171, P0172, P0335
and P0336 are not set.

•••••

long term adaption exceeds lean threshold is less
than or equal to 80 %.

Action Taken When the DTC Sets

•••••

The Malfunction Indicator Lamp (MIL) will illuminate
after two consecutive driving cycles in which the diag-
nostic runs with the fault active.

•••••

The ECM will record operating conditions at the time
the diagnostic fails. This information will be stored in
the Freeze Frame and Failure Records buffer.

•••••

A history DTC is stored.

Conditions for Clearing the MIL/DTC

•••••

The MIL will turn OFF after 3 consecutive driving
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 ECM
Initialization function to reset long term fuel trim to 1 (0
%).

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

MAF sensor - An output that causes the ECM to sense
a lower than normal mass air flow can cause the system
to go lean. Disconnecting the MAF sensor will allow the
ECM to substitute a fixed (default) value for the MAF
sensor. If the lean condition is gone when the sensor is
disconnected, substitute a known good sensor and re-
check.

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 a poor O2S 1 or MAF (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

Check for a damaged harness. Inspect wiring harness
for damage. If the harness appears to be OK, observe
the O2S 1 display on the scan tool while moving connec-
tors and 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.

Test Description

Number(s) below refer to the step(s) number on the
Diagnostic Table.

1. The Euro On-Board Diagnostic (EOBD) System

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

ENGINE CONTROLS 1F-229

SSANGYONG Y158

Step

Action

Value(s)

Yes

DTC P0171 Bank 1 System Too Lean

Go to Step 2

Go to “Euro

On-Board

Diagnostic

System Check”

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

Install the scan tool.
Are any component related to Diagnostic trouble Codes
(DTCs) set?
With the engine running, operate the vehicle until the
Loop Status indicates closed.
Is the Long Term Fuel Trim Bank 1 below the specified
value?
1. 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 the DTC as
noted.

Does the Long Term Fuel Trim Bank 1 below the
specified value?
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.

•••••

O2S 1 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 grouns are
clean, tight and in their proper locations.

Do any of the above checks isolate a condition requiring
repair?
1. Disconnect the Mass Air Flow (MAF or MAP) sensor

electrical connector.

2. Operate the vehicle in Closed Loop while monitoring

the Long Term Fuel Trim Bank 1.

Is the Long Term Fuel Trim Bank 1 below the specified
value?

20 %

Go to Step 14

Go to Step 5

the malfunction occurred. The information is stored
in the scan tool for later reference.

5. Visually/physically checking items which may

cause a lean condition may determine the cause of
the DTC being set and save diagnosis time.

9. A vacuum leak can change the Fuel trim index and

set DTC P0171. This step checks the intake
manifold for vacuum leaks.

10. Contaminants in fuel, such as alcohol or water, can

create a lean condition setting DTC P0171. Checking
for these contaminants could identify the
malfunction.

15. If no faults have been found at this point and no

additional DTCs were set, refer to ”Diagnostic Aids”
for additional checks and information.

20 %

Go to Step 13

Go to Step 9

20 %

Go to Step 4

Go to Step 5

Go to Step 7

Go to Step 6

Go to

applicable

DTC table

Go to Step 3

1F-230 ENGINE CONTROLS

SSANGYONG Y158

1. Repair the malfunction found in Step 5.
2. Check the Long Term Fuel Trim Bank 1 while

operating the engine.

Is the Long Term Fuel Trim Bank 1 below the specified
value?
Lean condition is not present.
Does a driveability problem exist?

Visually and physically inspect the following items for
vacuum leaks;

•••••

Intake manifold

•••••

Throttle body

•••••

Injector 1, 2 or 3 O-ring

•••••

Any other leaks

Do any of the above checks isolate a condition requiring
a repair?
Check the fuel for excessive water, alcohol, or other
contaminants and correct the contaminated fuel
condition if present.
Is the fuel contaminated?
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. 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?
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?
Replace the MAF (or MAP) sensor.
Is the action complete?
1. Using the scan tool, clear the 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 text.

Does the scan tool indicate that this diagnostic has run
and passed?
Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?

Step

Action

Value(s)

Yes

DTC P0171 Bank 1 System Too Lean (Cont’d)

20 %

Go to Step 8

Go to Step 9

Go to Step 14

Go to Step 10

Go to Step 14

Go to Step 11

Go to Step 14

Go to Step 15

Go to Step 2

3.8 bars

Go to Step 12

Go to “Fuel

System

Diagnosis”

0.6 bars

Go to “Fuel

Injector Balance

Test”

Go to “Fuel

System

Diagnosis”

Go to

“Symptoms

Diagnosis”

Go to Step 14

Go to

applicable

DTC table

System OK

ENGINE CONTROLS 1F-231

SSANGYONG Y158

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