Isuzu 1999 RODEO Workshop Manual page 1504

Diagnostic Trouble Code (DTC) P0304 Cylinder 4 Misfire Detected
Circuit Description
The powertrain control module (PCM) has the ability to
detect a misfire by monitoring the 58X reference and the
camshaft position sensor input signals.
detects a crankshaft speed variation that indicates 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 misfire, the PCM attempts
to calculate which cylinder is misfiring by associating
crankshaft angle (using the camshaft position sensor
signal) with the RPM variation (using the 58X reference).
If cylinder #4 is isolated as the misfiring cylinder, DTC
P0304 will 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, camshaft position sensor, vehicle speed
sensor, ECT sensor, ABS rough road sensor,
crankshaft position sensor.
f The engine speed is between 600 and 6250 RPM.
f The system voltage is between 11 and 16 volts.
f The ECT indicates an engine temperature between
–7°C (28°F) and 120°C (248°F).
f The throttle angle is steady.
f The PCM is detecting a crankshaft RPM variation that
indicates a misfire on cylinder #4 sufficient to cause
three-way catalytic converter damage or emissions
levels to exceed 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.
Step
1 Was the "On-Board Diagnostic (OBD) System Check"
performed?
2 1. Start the engine. Run the engine at idle.
2. Review and record Tech 2 Freeze Frame data.
3. Monitor "Misfire Cur. #4" on the Tech 2.
Is "Misfire Cur. #4" increasing (indicating a misfire
currently occurring)?
3 Monitor "Misfire Hist. #4" while operating the vehicle to
duplicate the conditions present when the DTC was set
(as defined by the Freeze Frame data recorded in Step
2).
Is "Misfire Hist. #4" increasing (indicating a misfire
currently occurring)?
RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS
If the PCM
DTC P0304 – Cylinder 4 Misfire Detected
Action
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 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 ignition cycle in which the diagnostic has
been run and the fault condition is no longer present.
f A history DTC P0304 will clear after 40 consecutive
ignition cycles occur without a fault.
f DTC P0304 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:
f System grounds – Ensure all connections are clean
and properly tightened.
f Injector – Perform the injector coil/balance test to
locate a faulty injector that contributes to a lean
condition on the affected cylinder. In addition to the
above test, check the condition of the injector O-ring.
f Faulty spark plug – Check for a cracked insulator,
carbon tracking, incorrect gap, and worn electrodes.
f Damaged or faulty ignition coil – Check for cracks,
carbon tracking 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.
Value(s)
Go to Step 2
—
Go to Step 4
—
— Go to Step 4
6E2–261
Yes No
Go to OBD
System
Check
Go to Step 3
Refer to
Diagnostic
Aids