Opel Frontera UBS. Manual - part 1199

 

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Opel Frontera UBS. Manual - part 1199

 

 

6E–162

ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0174 Fuel Trim System Lean Bank 2

D06RW031

Circuit 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 powertrain control module (PCM) monitors the Bank 1
HO2S 1 and Bank 2 HO2S 1 signals and adjusts fuel
delivery based upon the HO2S signal voltages.  A change
made to fuel delivery will be indicated by the long and
short term fuel trim values which can be monitored with a
Tech 2.  Ideal fuel trim values are around 0%; if the HO2S
signals are indicating a lean condition the PCM will add
fuel, resulting in fuel trim values above 0%.  If a rich
condition is detected, the fuel trim values will be below
0%, indicating that the PCM is reducing the amount of fuel
delivered.  If an excessively lean condition is detected on
Bank 2, the PCM will set DTC P0174.
The PCM’s maximum authority to control long term fuel
trim allows a range between –15%(automatic
transmission) or –12%(manual transmission)  and +20%.
The PCM monitors fuel trim under various engine

speed/load fuel trim cells before determining the status of
the fuel trim diagnostic.

Conditions for Setting the DTC

D

No Tech 2 test is being run.

D

None of the following DTCs are set: idle system, EGR,
HO2S, (response, transition, open, low volts, no
activity), MAF, TP sensor, MAP, IAT, canister purge,
EVAP, injector circuit, or misfire.

D

Engine coolant temperature is between 25

°

C (77

°

F)

and 100

°

C (212

°

F).

D

Intake air temperature is between –40

°

C (–40

°

F) and

120

°

C (248

°

F).

D

Manifold absolute pressure is between 24 kPa and 99
kPa.

D

Throttle angle is steady below 95%.

D

Vehicle speed is below 136 km/h (85 mph).

D

Engine speed is between 400 and 6,000 RPM.

D

Barometric pressure is greater than 72.5 kPa.

D

Mass air flow is between 2 g/second and 200 g/second.

6E–163

ENGINE DRIVEABILITY AND EMISSIONS

D

Ignition voltage is above 9.5 volts.

D

Fuel system is in “closed loop.”

Action Taken When the DTC Sets

D

The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
failure is detected.

D

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

Conditions for Clearing the MIL/DTC

D

DTC P0174 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

Check for the following conditions:

D

Poor connection at PCM – Inspect harness connectors
for backed-out terminals, improper mating, broken
locks, improperly formed or damaged terminals, and
poor terminal-to-wire connection.

D

Damaged harness – Inspect the wiring harness for
damage.  If the harness appears to be OK, observe the

Bank 2 HO2S 1 display on the Tech 2 while moving
connectors and wiring harnesses related to the engine
harness.  A change in the display will indicate the
location of the fault.

Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the DTC to be set occurs.  This
may assist in diagnosing the condition.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart.
2. DTCs other than P0171 and P0174 may indicate a

condition present which may cause a lean condition.
If this is the case, repairing the condition which
caused the other DTC will most likely correct the
DTC P0171/P0174.

4. If the DTC P0174 test passes while the Failure

Records conditions are being duplicated, the lean
condition is intermittent.  Refer to 

Diagnostic Aids or

Symptoms for additional information on diagnosing
intermittent problems.

6E–164

ENGINE DRIVEABILITY AND EMISSIONS

DTC P0174 – Fuel Trim System Lean Bank 2

 

Step

Action

Value(s)

Yes

No

1

Was the “On-Board Diagnostic (OBD) System Check”
performed?

Go to 

Step 2

Go to 

OBD

System

Check

2

Are any DTCs set other than P0174 and P0171?

Go to the

applicable

DTC charts

and repair the

other DTCs

before

proceeding

with this

chart.

Go to 

Step 3

3

1. Start the engine and operate the vehicle in “closed

loop.”

2. Observe the “BANK 2 L.T. FUEL TRIM” display on

the Tech 2.

Is the displayed values greater than the specified
values?

L.T. Fuel

Trim: +20%

Go to 

Step 5

Go to 

Step 4 

4

1. Review and record Tech 2 Failure Records data.
2. Clear the DTC P0171/P0174 and operate the

vehicle to duplicate the Failure Records conditions.

3. Monitor the Tech 2 “DTC” info for DTC P0174 while

operating the vehicle to duplicate the Failure
Records conditions.

4. Continue operating the vehicle until the DTC P0174

test runs.

5. Note the test result.

Does the Tech 2 indicate DTC P0174 failed this
ignition?

Go to 

Step 5

The lean

condition is

not present.

If a

driveability

symptom still

exists, refer

to 

Symptoms

section.

5

Was DTC P0171 also set?

Go to 

Step 6

Go to 

Step 15

6

Visually and physically inspect the vacuum hoses for
disconnects, splits, kinks, improper routing and
improper connections and repair any problem found.

Did your inspection reveal a problem requiring repair?

Verify repair 

Go to 

Step 7

7

Visually and physically inspect the crankcase
ventilation valve for proper installation and repair any
problem found (refer to 

Crankcase Ventilation

System).

Did your inspection reveal a problem requiring repair?

Verify repair

Go to 

Step 8

8

1. Inspect the MAF sensor inlet screen for damage or

for the presence of foreign objects which may
partially block the air flow sample through the MAF
sensor.

2. Correct any problem that is found as necessary.

Did your inspection of the MAF sensor reveal a
condition requiring repair?

Verify repair

Go to 

Step 9

9

Start the engine and note the idle quality.

Is a high or unsteady idle being experienced?

Go to 

Step 10

Go to 

Step 11

6E–165

ENGINE DRIVEABILITY AND EMISSIONS

DTC P0174 – Fuel Trim System Lean Bank 2

  (Cont'd)

Step

No

Yes

Value(s)

Action

10

1. Visually and physically inspect the throttle body,

intake manifold, EGR valve and the EGR feed pipe
for vacuum leaks.

2. Repair any vacuum leaks as necessary.

Did your inspection reveal a vacuum leak?

Verify repair

Go to 

Step 11

11

Check the fuel for excessive water, alcohol, or other
contaminants (see 

Diagnosis in Engine Fuel for

procedure) and correct the contaminated fuel condition
is present (see 

Engine Fuel).

Was the fuel contaminated?

Verify repair

Go to 

Step 12

12

1. Visually and physically inspect the PCM injector

grounds, power grounds and sensor grounds to
ensure that they are clean, tight, and in their proper
locations.

2. If a faulty ground condition is present, correct it as

necessary.

Did your inspection reveal a condition requiring repair?

Verify repair

Go to 

Step 13

13

1. Disconnect the MAF sensor electrical connector.
2. Operate the vehicle in “closed loop” while

monitoring the “BANK 1 S.T. FUEL TRIM” displayed
on the Tech 2.

Does the “BANK 1 S.T. FUEL TRIM” value decrease to
near the specified value?

0%

Go to 

Step 19

Go to 

Step 14

14

Perform the procedure in the ”Fuel System Pressure
Test” and repair fuel system problem if necessary.

Did the Fuel System Pressure Test isolate a condition
requiring repair?

Verify repair

Go to 

Step 15

15

1. Visually and physically inspect the intake manifold,

injector O-rings, EGR adapter, EGR valve and the
EGR feed pipes for vacuum leaks.

2. Repair any problem that is found.

Did your inspection reveal a problem?

Verify repair

Go to 

Step 16

16

Visually and physically inspect the Bank 2 exhaust
manifold for leaks and loose or missing hardware and
correct any problem found.

Did your inspection reveal a problem?

Verify repair

Go to 

Step 17

17

Perform the “Injector Balance Test,” and correct any
problem found (refer to 

Fuel Metering System).

Did the Injector Balance Test isolate a problem?

Verify repair 

Go to 

Step 18

18

1. Visually and physically inspect the Bank 2 HO2S 1

to ensure that it is installed securely and that the
Bank 2 HO2S 1 pigtail and wiring harness are not
contacting the exhaust or otherwise damaged.

2. If a problem is found, correct it as necessary.

Did your inspection reveal a problem?

Verify repair

Refer to

Diagnostic

Aids

19

Replace the MAF sensor.

Is the action complete?

Verify repair

 

 

 

 

 

 

 

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