Isuzu Rodeo UE. Service manual - part 436

6E2–499

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

A fuel injector which is stuck partly open will cause a loss
of fuel pressure after engine shut down, causing long
crank times.

0003

Fuel Metering System Components

The fuel metering system is made up of the following
parts:

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The fuel injectors.

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The throttle body.

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The fuel rail.

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The fuel pressure regulator.

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The PCM.

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The crankshaft position (CKP) sensor.

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The camshaft position (CMP) sensor.

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The idle air control (IAC) valve.

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The fuel pump.

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The fuel pump relay.

Basic System Operation
The fuel metering system starts with the fuel in the fuel
tank.  An electric fuel pump, located in the fuel tank,
pumps fuel to the fuel rail through an in-line fuel filter.  The
pump is designed to provide fuel at a pressure above the
pressure needed by the injectors.  A fuel pressure
regulator in the fuel rail keeps fuel available to the fuel
injectors at a constant pressure.  A return line delivers
unused fuel back to the fuel tank.  Refer to 

Section 6C for

further information on the fuel tank, line filter, and fuel
pipes.

Fuel Metering System Purpose

The basic function of the air/fuel metering system is to
control the air/fuel delivery to the engine.  Fuel is delivered
to the engine by individual fuel injectors mounted in the
intake manifold near each intake valve.
The main control sensor is the heated oxygen sensor
(HO2S) located in the exhaust system.  The HO2S tells
the PCM how much oxygen is in the exhaust gas.  The
PCM changes the air/fuel ratio to the engine by controlling
the amount of time that fuel injector is “ON.”  The best
mixture to minimize exhaust emissions is 14.7 parts of air

to 1 part of gasoline by weight, which allows the catalytic
converter to operate most efficiently.  Because of the
constant measuring and adjusting of the air/fuel ratio, the
fuel injection system is called a “closed loop” system.
The PCM monitors signals from several sensors in order
to determine the fuel needs of the engine. Fuel is
delivered under one of several conditions called “modes.”
All modes are controlled by the PCM.

Fuel Pressure Regulator

The fuel pressure regulator is a diaphragm-operated
relief valve mounted on the fuel rail with fuel pump
pressure on one side and manifold pressure on the other
side.  The fuel pressure regulator maintains the fuel
pressure available to the injector at three times
barometric pressure adjusted for engine load.  It may be
serviced separate.
If the pressure is too low, poor performance and a DTC
P0131, DTC P0151,DTC P0171 or DTC P1171 will be the
result.  If the pressure is too high, excessive odor and/or a
DTC P0132, DTC P0152,DTC P0172 or DTC P0175 will
be the result.  Refer to 

Fuel System Diagnosis for

information on diagnosing fuel pressure conditions.

0011

Fuel Pump Electrical Circuit

When the key is first turned “ON,” the PCM energizes the
fuel pump relay for two seconds to build up the fuel
pressure quickly.  If the engine is not started within two
seconds, the PCM shuts the fuel pump off and waits until
the engine is cranked.  When the engine is cranked and
the 58 X crankshaft position signal has been detected by
the PCM, the PCM supplies 12 volts to the fuel pump relay
to energize the electric in-tank fuel pump.
An inoperative fuel pump will cause a “no-start” condition.
A fuel pump which does not provide enough pressure will
result in poor performance.

Fuel Rail

The fuel rail is mounted to the top of the engine and
distributes fuel to the individual injectors.  Fuel is
delivered to the fuel inlet tube of the fuel rail by the fuel
lines.  The fuel goes through the fuel rail to the fuel

6E2–500

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

pressure regulator.  The fuel pressure regulator maintains
a constant fuel pressure at the injectors.  Remaining fuel
is then returned to the fuel tank.

055RV009

Idle Air Control (IAC) Valve

The purpose of the idle air control (IAC) valve is to control
engine idle speed, while preventing stalls due to changes
in engine load.  The IAC valve, mounted in the throttle
body, controls bypass air around the throttle plate.  By
moving the conical valve (pintle) in (to decrease air flow)
or out  (to increase air flow), a controlled amount of air can
move around the throttle plate.  If the RPM is too low, the
PCM will retract the IAC pintle, resulting in more air
moving past the throttle plate to increase the RPM.  If the
RPM is too high, the PCM will extend the IAC pintle,
allowing less air to move past the throttle plate,
decreasing the RPM.
The IAC pintle valve moves in small steps called counts.
During idle, the proper position of the IAC pintle is
calculated by the PCM based on battery voltage, coolant
temperature, engine load, and engine RPM.  If the RPM
drops below a specified value,  and the throttle plate is
closed, the PCM senses a near-stall condition. The PCM
will then calculate a new IAC pintle valve position to
prevent stalls.
If the IAC valve is disconnected and reconnected with the
engine running, the idle RPM will be wrong.  In this case,
the IAC must be reset.  The IAC resets when the key is
cycled “ON” then “OFF.”  When servicing the IAC, it
should only be disconnected or connected with the
ignition “OFF.”
The position of the IAC pintle valve affects engine start-up
and the idle characteristics of the vehicle.  If the IAC pintle
is fully open, too much air will be allowed into the manifold.
This results in high idle speed, along with possible hard
starting and a lean air/fuel ratio.  DTC P0507 or DTC
P1509 may set.  If the IAC pintle is stuck closed, too little
air will be allowed in the manifold.  This results in a low idle
speed, along with possible hard starting and a rich air/fuel
ratio.  DTC P0506 or DTC P1508 may set.  If the IAC
pintle is stuck part-way open, the idle may be high or low
and will not respond to changes in the engine load.

0006

Run Mode

The run mode has the following two conditions:

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Open loop

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Closed loop

When the engine is first started the system is in “open
loop” operation.  In “open loop,” the PCM ignores the
signal from the heated oxygen sensor (HO2S).  It
calculates the air/fuel ratio based on inputs from the TP,
ECT, and MAF sensors.
The system remains in “open loop” until the following
conditions are met:

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The HO2S has a varying voltage output showing that
it is hot enough to operate properly (this depends on
temperature).

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The ECT has reached a specified temperature.

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A specific amount of time has elapsed since starting
the engine.

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Engine speed has been greater than a specified RPM
since start-up.

The specific values for the above conditions vary with
different engines and are stored in the programmable
read only memory (PROM).  When these conditions are
met, the system enters “closed loop” operation.  In
“closed loop,” the PCM calculates the air/fuel ratio
(injector on-time) based on the signal from the HO2S.
This allows the air/fuel ratio to stay very close to 14.7:1.

Starting Mode

When the ignition is first turned “ON,” the PCM energizes
the fuel pump relay for two seconds to allow the fuel pump
to build up pressure.  The PCM then checks the engine
coolant temperature (ECT) sensor and the throttle
position (TP) sensor to determine the proper air/fuel ratio
for starting.
The PCM controls the amount of fuel delivered in the
starting mode by adjusting how long the fuel injectors are
energized by pulsing the injectors for very short times.

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RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

Throttle Body Unit

The throttle body has a throttle plate to control the amount
of air delivered to the engine.  The TP sensor and IAC
valve are also mounted on the throttle body.  Vacuum
ports located behind the throttle plate provide the vacuum
signals needed by various components.
Engine coolant is directed through a coolant cavity in the
throttle body to warm the throttle valve and to prevent
icing.

0019

General Description (Electronic
Ignition System)

Camshaft Position (CMP) Sensor

The camshaft position (CMP) sensor is located on the
timing cover near the camshaft sprocket.  As the
camshaft sprocket turns, a magnet in the sprocket
activates the Hall-effect switch in the CMP sensor.  When
the Hall-effect switch is activated, it grounds the signal
line to the PCM, pulling the camshaft position sensor
signal circuit’s applied voltage low. This is a CMP signal.
The CMP signals is created as piston #1 is approximately
25

°

 after top dead counter on the power stroke.  If the

correct CMP signal is not received by the PCM, DTC
P0341 will be set.

0014

Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor provides a signal
used by the powertrain control module (PCM) to calculate
the ignition sequence.  The sensor initiates the 58X
reference pulses which the PCM uses to calculate RPM
and crankshaft position.  Refer to 

Electronic Ignition

System for additional information.

Electronic Ignition

The electronic ignition system controls fuel combustion
by providing a spark to ignite the compressed air/fuel
mixture at the correct time.  To provide optimum engine
performance, fuel economy, and control of exhaust
emissions, the PCM controls the spark advance of the
ignition system.  Electronic ignition has the following
advantages over a mechanical distributor system:

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No moving parts.

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Less maintenance.

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Remote mounting capability.

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No mechanical load on the engine.

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More coil cooldown time between firing events.

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Elimination of mechanical timing adjustments.

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Increased available ignition coil saturation time.

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RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

0013

Ignition Coils

A separate coil-at-plug module is located at each spark
plug.  The coil-at-plug module is attached to the engine
with two screws.  It is installed directly to the spark plug by
an electrical contact inside a rubber boot.  A three-way
connector provides 12-volt primary supply from the
15-amp ignition fuse, a ground-switching trigger line from
the PCM, and a ground.

0001

Ignition Control

The ignition control (IC) spark timing is the PCM’s method
of controlling the spark advance and the ignition dwell.
The IC spark advance and the ignition dwell are
calculated by the PCM using the following inputs:

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Engine speed.

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Crankshaft position (58X reference).

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Camshaft position (CMP) sensor.

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Engine coolant temperature (ECT) sensor.

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Throttle position (TP) sensor.

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Knock signal (knock sensor).

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Park/Neutral position (PRNDL input).

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Vehicle speed (vehicle speed sensor).

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PCM and ignition system supply voltage.

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The crankshaft positron (CKP) sensor sends the
PCM a 58X signal related to the exact position of the
crankshaft.

TS22909

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The camshaft position (CMP) sensor sends a signal
related to the position of the camshaft.

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The knock sensor tells the PCM if there is any
problem with pre-ignition or detonation.  This
information allows the PCM to retard timing, if
necessary.

TS24037

Based on these sensor signals and engine load
information,  the PCM sends 5V to each ignition coil.