Isuzu Trooper (1998-2002 year). Manual — part 469
6E–246
6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0300 Engine Misfire Detected
Circuit Description
Misfire is monitored as a function of the combustion
quality (CQ) signals generated from the ION Sensing
Module. Combustion signals represent the degree of
combustion in each cylinder. Misfire is detected when the
combustion signal is below a predetermined value.
This DTC P0300 will determine if a multiple cylinder
misfire is occurring by monitoring the Combustion
Quality.
Conditions for Setting the DTC
D
None of the following DTCs occur: TP sensor, MAF
sensor, VSS, ECT sensor.
D
The engine speed is between 600 and 6250 RPM.
D
The system voltage is between 11 and 16 volts.
D
The engine temperature sensor (ECT) indicates an
engine temperature between –7
°
C (20
°
F) and 110
°
C
(230
°
F).
D
Throttle angle is steady and throttle changes less than
2% per 125 milliseconds.
Action Taken When the DTC Sets
D
The PCM will ON the MIL after second trip with
detected the fault.
D
If the misfire is severe enough to cause possible
catalyst damage, the PCM will flash the MIL for as long
as the misfire remains at catalyst damaging levels.
D
The PCM will disable the TCC operation.
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 in which the diagnostic has been
run and the fault condition is no longer present.
D
A history DTC P0300 will clear after 40 consecutive
warm-up cycles occur without a fault.
D
DTC P0300 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.
Diagnostic Aids
The Tech 2 display “Misfire Cur. #1 through #6” can be
useful to determine whether the misfire is isolated to a
single cylinder.
D
Damaged or faulty ignition coil – Check for cracks or
other damage.
D
Substitute a known good coil – Swap the ignition coils
and retest. If the misfire follows the coil, replace the
ignition coil.
If the misfire is random, check for the following conditions:
D
System grounds – Ensure all connections are clean
and properly tightened.
D
MAF – A mass air flow (MAF) sensor output that
causes the PCM to sense a lower than normal air flow
will cause a lean condition.
D
Air induction system – Air leaks into the induction
system which bypass the MAF sensor will cause a lean
condition. Check for disconnected or damaged
vacuum hoses, incorrectly installed or faulty PCV
valve, or for vacuum leaks at the throttle body, EGR
valve, and intake manifold mounting surfaces.
D
Fuel pressure – Perform a fuel system pressure test.
A faulty fuel pump, plugged filter, or faulty fuel system
pressure regulator will contribute to a lean condition.
D
Injector(s) – Perform an injector coil/balance test to
locate faulty injector(s) contributing to a lean or
flooding condition. In addition to the above test, check
the condition of the injector O-rings.
D
EGR – Check for a leaking valve, adapter, or feed pipes
which will contribute to a lean condition or excessive
EGR flow.
D
Fuel quality – Using fuel with the wrong octane rating
for the vehicle may cause driveability problems.
Although alcohol-enhanced fuels may raise the octane
rating, the fuel’s ability to turn into vapor in cold
temperatures deteriorates. This may affect the cold
driveability of the engine. The Reid Vapor Pressure of
the fuel can also create problems in the fuel system,
especially during the spring and fall when changes by
the refineries may not coincide with changes in the
weather.
D
Vehicle marshalling – The transportation of new
vehicles from the assembly plant to the dealership can
involve as many as 60 key cycles within 2 to 3 miles of
driving. This type of operation contributes to the fuel
fouling of the spark plugs and will turn on the MIL with
a P0300 Misfire DTC.
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.
6E–247
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0300 – Engine Misfire Detected
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
1. Start the engine. Run the engine at idle.
2. Review and record the Tech 2 Freeze Frame data.
3. Operate the vehicle to duplicate the conditions
present when the DTC was set (as defined by the
Freeze Frame data).
4. Monitor the Tech 2 “Misfire Cur. #” display for each
cylinder.
Is “Misfire Cur. #” display increasing for any cylinder
(indicating a misfire currently occurring)?
—
Go to
Step 3
Check the
Procedure
Refer to
Diagnostic
Aids
3
1. Visually and physically inspect the vacuum hoses
for splits, kinks, and improper connections.
2. If a problem is found, repair or replace the vacuum
hoses as necessary.
Did your inspection reveal a problem?
—
Verify repair
Go to
Step 4
4
1. Visually and physically inspect the following areas
for vacuum leaks:
D
The intake manifold
D
The injector O-rings
D
The EGR adapter
D
The EGR feed pipes
D
ION Sensing Module
2. If a problem is found, repair the vacuum leak as
necessary.
Did your inspection reveal a vacuum leak?
—
Verify repair
Go to
Step 5
5
1. Visually and physically inspect the crankcase
ventilation valve for improper installation or
damaged grommet.
2. If a problem is found, repair as necessary (refer to
Crankcase Ventilation System).
Did your inspection reveal a problem?
—
Verify repair
Go to
Step 6
6
1. Inspect the MAF sensor inlet screen for damage or
for the presence of foreign objects that may partially
block the air flow sample through the MAF sensor.
2. If a problem is found, repair or replace the MAF
sensor as necessary.
Did your inspection of the MAF sensor reveal a
condition requiring repair or replacement?
—
Verify repair
Go to
Step 7
7
1. Remove the EGR valve and visually/physically
inspect the valve to ensure that the pintle is not
sticking partially open. Also, inspect the EGR valve
pintle and seat for carbon deposits or burrs that may
interfere with the pintle closing completely.
2. If a problem is found, clean the EGR valve pintle and
seat or replace the EGR valve as necessary.
Did your inspection reveal a problem?
—
Verify repair
Go to
Step 8
6E–248
6VE1 3.5 ENGINE DRIVEABILITY AND EMISSIONS
DTC P0300 – Engine Misfire Detected
(Cont'd)
Step
No
Yes
Value(s)
Action
8
1. Install a spark tester at the spark plug end of the
ignition coil for a cylinder that indicated a misfire.
2. Crank the engine while observing the spark tester.
A crisp, blue spark should be observed.
Is adequate spark present?
—
Go to
Step 14
Go to
Step 9
9
1. Remove and visually/physically inspect the ignition
coil(s) associated with the cylinders that were
indicated as misfiring. Ensure that the coil(s) are
free of cracks.
2. If a problem is found, replace the damaged ignition
coil(s) as necessary.
Did any ignition coils require replacement?
—
Verify repair
Go to
Step 10
10
1. Remove the spark plugs from the cylinders that
were indicated as misfiring.
2. Visually inspect the spark plug electrodes.
Does your inspection reveal any spark plugs exhibiting
excessive fouling?
—
Go to
Engine
Mechanical
Diagnosis
Go to
Step 11
11
1. Visually inspect the spark plug insulators for cracks,
carbon tracking, or other damage.
2. If a problem is found, replace the faulty spark
plug(s) as necessary.
Did your inspection reveal a problem?
—
Verify repair
Go to
Step 12
12
1. Disconnect the MAF sensor electrical connector.
2. Operate the vehicle in “closed loop” while
monitoring the “BANK 1 L.T. FUEL TRIM” and
“BANK 1 S.T. FUEL TRIM” display on the Tech 2.
Do both values decrease below the specified values?
”BANK 1 L.T.
FUEL TRIM”
below +20%;
“BANK 1 S.T.
FUEL TRIM”
below +50%
Go to
Step 13
Replace the
ignition coil of
the affected
cylinder
13
Replace the ignition coil control module.
Is the action complete?
—
Verify repair
—
14
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 problem is found, correct the faulty ground
condition as necessary.
Did your inspection reveal a poor ground?
—
Verify repair
Go to
Step 15
15
1. Perform the “Fuel System Pressure Test”
procedure.
2. If a problem is found, repair as necessary (refer to
Engine Fuel or Fuel Metering System).
Was a fuel system problem found?
—
Verify repair
Go to
Step 16
16
1. Check the fuel for excessive water, alcohol, or other
contaminants (refer to
Diagnosis in Engine Fuel for
procedure).
2. If a problem is found, correct the contaminated fuel
condition as necessary.
Was the fuel contaminated?
—
Verify repair
Go to
Step 17
6E–249
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
DTC P0300 – Engine Misfire Detected
(Cont'd)
Step
No
Yes
Value(s)
Action
17
1. Perform the “Injector Coil/Balance Test”.
2. If a problem is found, replace faulty injector(s) as
necessary.
Did any of the injectors require replacement?
—
Verify repair
Go to
Step 18
18
1. Check for an engine mechanical problem. Refer to
Engine Mechanical Diagnosis to diagnose the
following conditions:
D
A faulty or incorrect camshaft
D
Leaking or sticky valves or rings
D
Excessive valve deposits
D
Weak valve springs
D
Incorrect valve timing
D
A leaking head gasket
D
A loose or broken motor mount
2. If a problem is found, repair as necessary.
Was a basic engine mechanical problem found and
repaired?
—
Verify repair
Go to
Step 19
19
1. Check for a transmission TCC problem. Refer to
4L30-E Automatic Transmission Diagnosis.
2. If a problem is found, repair the transmission as
necessary. Refer to
4L30-E Automatic
Transmission Unit Repair.
Was a transmission problem found and repaired?
—
Verify repair
Go to
Step 20
20
Replace the MAF sensor.
Is the action complete?
—
Verify repair
—
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