Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1284

6E1–212

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DIAGNOSTIC TROUBLE CODE (DTC)

P0303 RANDOM/MULTIPLE CYLINDER MISFIRE DETECTED

060R100034

Circuit Description

If the PCM determines that the engine is misfiring and can
determine the actual cylinder that is misfiring then it will
log the individual trouble code for that cylinder P0303.
This is normally the situation in the case of a failed fuel
injector, spark plug or ignition lead.

Conditions for Setting the DTC

None of the following Diagnostic Trouble Codes are
present: TP sensor, MAP sensor, CMP sensor, VSS,
ECT, CKP sensor.

The engine speed is between 687 and 6250 RPM.

The system voltage is between 11 and 16 volts.

The engine coolant temperature sensor (ECT)
indicates an engine temperature between –6.75

(20

F) and 120

C (248

F).

Throttle angle is steady and throttle angle changes less
than 2.73% per 100 milliseconds.

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.

TP sensor reads less than 3.125%.

Vehicle speed is greater than 19km/h (12mph).

Fuel level is more than 14.8%.

ECT is less than –7.0

C (19.4

F) at startup engine.

ECT is less than 20.75

C (69.35

F) and 120

(248

F).

Rough road table based on rough road valve from ABS
vs vehicle speed.

Decelation index versus engine speed versus load and
crank position.

Emission damage misfire ratio more than 2.00%.

Catalyst damage misfire ratio 11–25%.

Emission level is 5 failed 200 revolution blocks out of 16.
Catalyst Damage level is 4 of 16 failed 200 engine cycle
blocks.

Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

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.

”Open Loop” fuel control will be in effect.

The PCM will store conditions which were present
when the Diagnostic Trouble Code was set as Freeze
Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC

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.

A history Diagnostic Trouble Code P0303 will clear
after 40 consecutive warm–up cycles have occurred
without a fault.

6E1–213

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Diagnostic Trouble Code P0303 can be cleared by
using the Scan Tool’s ”Clear Info” function.

Diagnostic Aids

The Tech 2 displays ”Misfire Cur. # 1 through #4” can be
useful to determine whether the misfire is isolated to a
single cylinder.

Damaged or faulty ignition coils – Check for cracks or
other damage.

Substitute a known good coil – Swap the ignition coils
and retest. If misfire follows the coil, replace the ignition
coil.

If the misfire is random, check for the following conditions:

System grounds – Ensure all connections are clean
and properly tightened.

Air induction system – 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.

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.

Excessive engine vibration – This may falsely set a
P0303. Refer to Engine Mechanical Diagnosis to
check for a falsely Mechanical condition or component.

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.

EGR – Check for a leaking valve, adapter, or feed pipes
which will contribute to a lean condition or excessive
EGR flow.

Reviewing the Failure Records vehicle mileage since the
diagnostic test last failed may help determine how often
the condition that caused the Diagnostic Trouble Code to
be set occurs. This may assist in diagnosing the
condition.

6E1–214

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DTC P0303 – Random/Multiple Cylinder Misfire Detected

Step

Action

Value(s)

Yes

Was the ”On–Board Diagnostic (OBD) System Check”
performed?

—

Go to Step 2

Go to OBD

System

Check

1. Start and idle the engine.
2. Review and record the Tech 2 Freeze Frame data.
3. Operate the vehicle to duplicate the conditions

present when the Diagnostic Trouble Code 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

Refer to

Diagnostic

Aids

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

1. Visually and physically inspect the following areas

for vacuum leaks:

Intake manifold

Injector O–rings

EGR valve

EGR feed pipes

Did your inspection reveal a vacuum leak?

—

Verify repair

Go to Step 5

Inspect the crankcase ventilation valve for proper
installation or a cracked hose.

Did your inspection reveal a problem?

—

Verify repair

Go to Step 6

1. Remove and visually/physically inspect the ignition

coils. Ensure that the coils are free of cracks and
carbon tracking.

2. If a problem is found, replace the damaged ignition

coils.

Was a problem found?

—

Verify repair

Go to Step 7

1. Install a spark tester at the spark plug end of the

ignition wire for the cylinder that is indicated by the
”Misfire Cur. Counters” or ”Misfire Hist. Counters”
as having the most severe misfire (largest number
of counts).

2. Crank the engine while observing the spark tester. A

crisp, blue spark should be observed.

Is adequate spark present?

—

Go to Step

Go to Step 8

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 9

6E1–215

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

DTC P0303 – Random/Multiple Cylinder Misfire Detected

(Cont'd)

Step

Yes

Value(s)

Action

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

Replace the ignition control module.

—

Verify repair

—

1. 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

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

1. Check the fuel for excessive water, alcohol, or other

contaminants (refer to Diagnosis in Engine Fuel for
procedure).

Was the fuel contaminated?

—

Verify repair

Go to Step

1. Perform the ”Injector Coil/Balance Test.”
2. If a problem is found, replace the faulty injector(s) as

necessary.

Did any of the injectors require replacement?

—

Verify repair

Go to Step

Check for an engine mechanical problem. Refer to
Engine Mechanical Diagnosis to diagnose the following
conditions:

A faulty or incorrect camshaft

Leaking or sticky valves or piston rings

Excessive valve deposits

Loose or worn rocker arms

Weak valve springs

Incorrect valve timing

A leaking head gasket

A loose or broken motor mount

—

Verify repair

—

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