P0300 Engine Misfire Detected - Isuzu 2000 Trooper Workshop Manual

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 system. 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 120°C
(248°F).
D Throttle angle is steady and throttle changes less than
15% per 125 milliseconds.
Action Taken When the DTC Sets
D The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.
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.
TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
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–259