Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual — part 1443
6E2–223
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
D
DTC P0171 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 1 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 P0171 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.
6E2–224
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0171 – Fuel Trim System Lean Bank 1
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 P0171 and P0174?
—
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 1 L.T. FUEL TRIM” display on
the Tech 2.
Is the displayed value greater than the specified value?
L.T. Fuel
Trim: +20%
Go to
Step 5
Go to
Step 4
4
1. Review and record the 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 P0171 while
operating the vehicle to duplicate the Failure
Records conditions.
4. Continue operating the vehicle until the DTC P0171
test runs and note the test result.
Does the Tech 2 indicate DTC P0171 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 P0174 also set?
—
Go to
Step 6
Go to
Step 15
6
Visually and physically inspect the vacuum hoses for
disconnections, 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
Step11
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
6E2–225
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0171 – Fuel Trim System Lean Bank 1
(Cont'd)
Step
No
Yes
Value(s)
Action
11
Check the fuel for excessive water, alcohol, or other
contaminants (see
Diagnosis in Engine Fuel for the
procedure) and correct the contaminated fuel condition
if 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 “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 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 1 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 Injector Balance Test isolate a problem?
—
Verify repair
Go to
Step 18
18
1. Visually and physically inspect the Bank 1 HO2S 1
to ensure that it is installed securely and that the
Bank 1 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
—
6E2–226
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0172 Fuel Trim System Rich Bank 1
060R200054
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
heated oxygen sensors (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
rich condition is detected on Bank 1, the PCM will set DTC
P0172.
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’s maximum authority to control short term fuel
trim allows a range between –11% 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
None of the following was set: EGR DTCs, HO2S
DTCs, (response, transition, open, low volts, no
activity), MAF DTCs, TPS DTCs, MAP DTCs, IAT
DTCs, canister purge DTCs, EVAP DTCs, injector
circuit DTCs, or misfire DTCs.
D
Engine coolant temperature is between 6
°
C (42.8
°
F)
and 105
°
C (221
°
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.
D
Ignition voltage is above 9.5 volts.
D
Fuel system is in “closed loop”.
D
Canister purge duty cycle is greater than 0%, if “ON”.
Action Taken When the DTC Sets
D
The PCM will illuminate the malfunction indicator lamp
(MIL) after the second consecutive trip in which the
fault 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
The PCM will turn the MIL “OFF” on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condition is no longer present.
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