Isuzu Rodeo UE. Manual — part 374
6E2–251
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Trouble Code (DTC) P0300 Engine Misfire Detected
Circuit Description
The powertrain control module (PCM) is able to detect a
misfire by monitoring the 58X reference and the camshaft
position input signals. If the PCM detects crankshaft
speed variations that indicate 1% or more of cylinder firing
events are misfires, the PCM will disable the torque
converter clutch (TCC). If the RPM variation detected
indicates a true misfire condition, DTC P0300 will be set.
If the ABS Rough Road sensor input signal to the PCM
determines that a rough road condition is present, the
misfire diagnostic will be temporarily disabled.
Conditions for Setting the DTC
f
None of the following DTCs occur: TP sensor, MAF
sensor, CMP sensor, VSS, ECT sensor, ABS rough
road sensor, CKP sensor.
f
The engine speed is between 600 and 6250 RPM.
f
The system voltage is between 11 and 16 volts.
f
The engine temperature sensor (ECT) indicates an
engine temperature between –7
°
C (20
°
F) and 120
°
C
(248
°
F).
f
Throttle angle is steady and throttle changes less than
3% per 125 milliseconds.
f
The PCM detects a crankshaft RPM variation
indicating a misfire that is sufficient to cause catalytic
converter damage or emissions levels to exceed the
mandated standard.
Action Taken When the DTC Sets
f
The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
f
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.
f
The PCM will disable the TCC operation.
f
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
f
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.
f
A history DTC P0300 will clear after 40 consecutive
warm-up cycles occur without a fault.
f
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.
f
Damaged or faulty ignition coil – Check for cracks or
other damage.
f
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:
f
System grounds – Ensure all connections are clean
and properly tightened.
f
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.
f
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.
f
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.
f
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.
f
EGR – Check for a leaking valve, adapter, or feed pipes
which will contribute to a lean condition or excessive
EGR flow.
f
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.
f
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.
6E2–252
RODEO 6VD1 3.2L 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 Current Cyl #” display for
each cylinder.
Is “Misfire Cur. #” display increasing for any cylinder
(indicating a misfire currently occurring)?
—
Go to
Step 3
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:
f
The intake manifold
f
The injector O-rings
f
The EGR adapter
f
The EGR feed pipes
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
6E2–253
RODEO 6VD1 3.2L 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 “B1 Long Term Fuel Trim” and “B1
Short Term 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.
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
6E2–254
RODEO 6VD1 3.2L 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:
f
A faulty or incorrect camshaft
f
Leaking or sticky valves or rings
f
Excessive valve deposits
f
Loose or worn rocker arms
f
Weak valve springs
f
Incorrect valve timing
f
A leaking head gasket
f
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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