2002 ISUZU AXIOM sensor

6E±579
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
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 ªmodes.º
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 separtely.
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 will be the result.
Refer to
Fuel System Diagnosis for information on
diagnosing fuel pressure conditions.
014RY00010
Fuel Pump Electrical Circuit
When the key is first turned ªON,º 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 ªno-startº 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
pressure regulator. The fuel pressure regulator maintains
a constant fuel pressure at the injectors. Remaining fuel
is then returned to the fuel tank.
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Run Mode
The run mode has the following two conditions:

Open loop

Closed loop
When the engine is first started the system is in ªopen
loopº operation. In ªopen loop,º 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 ªopen loopº until the following
conditions are met:

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

The ECT has reached a specified temperature.

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

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 ªclosed loopº operation. In
ªclosed loop,º 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 ªON,º 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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6VE1 3.5L 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 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.
025RY00005
General Description (Electronic
Ignition System)
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
section 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:

No moving parts.

Less maintenance.

Remote mounting capability.

No mechanical load on the engine.

More coil cooldown time between firing events.

Elimination of mechanical timing adjustments.

Increased available ignition coil saturation time.
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.
060RY00022
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:

Engine speed.

Crankshaft position (58X reference).

Engine coolant temperature (ECT) sensor.

Throttle position (TP) sensor.

ION sensing module.

Park/Neutral position (PRNDL input).

6E±581
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Vehicle speed (vehicle speed sensor).

PCM and ignition system supply voltage.

The crankshaft position (CKP) sensor sends the PCM
a 58X signal related to the exact position of the
crankshaft.
TS22909Based on these sensor signals and engine load
information, the PCM sends 5V to each ignition coil.
060RY00116This module has the function to energize and de-energize
the primary ignition coil in response to signals from the
PCM. The Throttle PCM controls ignition timing and dwell
time.
Continuity and out-or-range value check:
This diagnosis detects open circuit or short-circuiting in
the Electronic Spark Timing (EST) line by monitoring EST
signals. A failure determination is made when the signal
voltage remains higher or lower than the threshold for
corresponding fault code beyond a predetermined time
period.
Diagnosis enabling conditions are as follows:

RPM is higher than the specified threshold.
EST line is enabled.
060RY00029
Ignition Control PCM Output
The PCM provides a zero volt (actually about 100 mV to
200 mV) or a 5-volt output signal to the ignition control (IC)
module. Each spark plug has its own primary and
secondary ignition coil assembly (ºcoil-at-plugº) located
at the spark plug itself. When the ignition coil receives the
5-volt signal from the PCM, it provides a ground path for
the B+ supply to the primary side of the coil-at -plug
module. When the PCM shuts off the 5-volt signal to the
ION sensing module, the ground path for the primary coil
is broken. The magnetic field collapses and induces a
high voltage secondary impulse which fires the spark plug
and ignites the air/fuel mixture.
The circuit between the PCM and the ignition coil is
monitored for open circuits, shorts to voltage, and shorts
to ground. If the PCM detects one of these events, it will
set one of the following DTCs:

P0351: Ignition coil Fault on Cylinder #1

P0352: Ignition coil Fault on Cylinder #2

P0353: Ignition coil Fault on Cylinder #3

P0354: Ignition coil Fault on Cylinder #4

P0355: Ignition coil Fault on Cylinder #5

P0356: Ignition coil Fault on Cylinder #6
Powertrain Control Module (PCM)
The PCM is responsible for maintaining proper spark and
fuel injection timing for all driving conditions. To provide
optimum driveability and emissions, the PCM monitors
the input signals from the following components in order
to calculate spark timing:

Engine coolant temperature (ECT) sensor.

Intake air temperature (IAT) sensor.

Mass air flow (MAF) sensor.

PRNDL input from transmission range switch.

Throttle position (TP) sensor.

Vehicle speed sensor (VSS) .

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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Crankshaft position (CKP) sensor.
Spark Plug
Although worn or dirty spark plugs may give satisfactory
operation at idling speed, they frequency fail at higher
engine speeds. Faulty spark plugs may cause poor fuel
economy, power loss, loss of speed, hard starting and
generally poor engine performance. Follow the
scheduled maintenance service recommendations to
ensure satisfactory spark plug performance. Refer to
Maintenance and Lubrication section.
Normal spark plug operation will result in brown to
grayish-tan deposits appearing on the insulator portion of
the spark plug. A small amount of red-brown, yellow, and
white powdery material may also be present on the
insulator tip around the center electrode. These deposits
are normal combustion by-products of fuels and
lubricating oils with additives. Some electrode wear will
also occur. Engines which are not running properly are
often referred to as ªmisfiring.º This means the ignition
spark is not igniting the air/fuel mixture at the proper time.
While other ignition and fuel system causes must also be
considered, possible causes include ignition system
conditions which allow the spark voltage to reach ground
in some other manner than by jumping across the air gap
at the tip of the spark plug, leaving the air/fuel mixture
unburned. Refer to
DTC P0300. Misfiring may also occur
when the tip of the spark plug becomes overheated and
ignites the mixture before the spark jumps. This is
referred to as ªpre-ignition.º
Spark plugs may also misfire due to fouling, excessive
gap, or a cracked or broken insulator. If misfiring occurs
before the recommended replacement interval, locate
and correct the cause.
Carbon fouling of the spark plug is indicated by dry, black
carbon (soot) deposits on the portion of the spark plug in
the cylinder. Excessive idling and slow speeds under
light engine loads can keep the spark plug temperatures
so low that these deposits are not burned off. Very rich
fuel mixtures or poor ignition system output may also be
the cause. Refer to DTC P0172.
Oil fouling of the spark plug is indicated by wet oily
deposits on the portion of the spark plug in the cylinder,
usually with little electrode wear. This may be caused by
oil during break-in of new or newly overhauled engines.
Deposit fouling of the spark plug occurs when the normal
red-brown, yellow or white deposits of combustion by
products become sufficient to cause misfiring. In some
cases, these deposits may melt and form a shiny glaze on
the insulator around the center electrode. If the fouling is
found in only one or two cylinders, valve stem clearances
or intake valve seals may be allowing excess lubricating
oil to enter the cylinder, particularly if the deposits are
heavier on the side of the spark plug facing the intake
valve.
TS23995Excessive gap means that the air space between the
center and the side electrodes at the bottom of the spark
plug is too wide for consistent firing. This may be due to
improper gap adjustment or to excessive wear of the
electrode during use. A spark plug gap that is too small
may cause an unstable idle condition. Excessive gap
wear can be an indication of continuous operation at high
speeds or with engine loads, causing the spark to run too
hot. Another possible cause is an excessively lean fuel
mixture.
TS23992Low or high spark plug installation torque or improper
seating can result in the spark plug running too hot and
can cause excessive center electrode wear. The plug
and the cylinder head seats must be in good contact for
proper heat transfer and spark plug cooling. Dirty or
damaged threads in the head or on the spark plug can
keep it from seating even though the proper torque is
applied. Once spark plugs are properly seated, tighten
them to the torque shown in the Specifications Table. Low
torque may result in poor contact of the seats due to a
loose spark plug. Overtightening may cause the spark
plug shell to be stretched and will result in poor contact

6E±585
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
140R200004
Legend
(1) Fuel Filler Cap
(2) Fuel Tank
(3) Rollover Valve
(4) Fuel Pump and Sender Assembly
(5) Fuel Filter
(6) Fuel Rail Right
(7) Right Bank
(8) Fuel Rail Left
(9) Left Bank(10) Fuel Pressure Control Valve
(11) Common Chamber
(12) Duty Solenoid Valve (EVAP Purge Solenoid)
(13) Throttle Valve
(14) Canister (EVAP Canister)
(15) Vent Hose
(16) Vent Solenoid Valve
(17) Separator
(18) Shut off Valve (With Over Pressure Relief
Valve) and Vapor Pressure Sensor

6E±586
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Electrical Components
The electrical components that make up the enhanced
EVAP system are:

Fuel Tank (Vapor) Pressure Sensor. The fuel tank
pressure sensor is a three-wire strain gauge sensor
similar to a common MAP sensor. However, the fuel
tank pressure sensor has very different electrical
characteristics due to its pressure differential design.
The sensor measures the difference between the air
pressure (or vacuum) in the fuel tank and the outside
air pressure.
The sensor mounts at the top of the fuel pump
assembly. A three-wire electrical harness connects it to
the PCM. The PCM supplies a five-volt reference
voltage and a ground to the sensor. The sensor will
return a voltage between 0.1 and 4.9 volts. When the
air pressure in the fuel tank is equal to the outside air
pressure, such as when the fuel cap is removed, the
output voltage of the sensor will be 1.3 to 1.7 volts.
When the air pressure in the fuel tank is 4.5 in. H2O
(1.25 kPa), the sensor output voltage will be 0.5 + 0.2 V.
When there is neither vacuum nor pressure in the fuel
tank, the sensor voltage will be 1.5 V. At ±14 in. H2O
(±3.75 kPa), the sensor voltage will be 4.5 + 0.2 V.

EVAP Canister Purge Solenoid. Normally closed, the
purge solenoid opens upon the PCM's signal to allow
engine vacuum to purge gasoline fumes from the
canister. Mounted on the water pipe to front of the
engine assembly.
060R200080

EVAP Canister Vent Solenoid. Located next to the
canister, the vent solenoid opens to allow air into the
EVAP system. Fresh air is necessary to completely
remove gasoline fumes from the canister during
purge. The EVAP vent solenoid closes to seal off the
evaporative emissions system for leak testing.
060R200081

Fuel Level Sensor. The fuel level sensor is an
important input to the PCM for the enhanced EVAP
system diagnostic. The PCM needs fuel level
information to know the volume of fuel in the tank.
The fuel level affects the rate of change of air
pressure in the EVAP system. Several of the
enhanced EVAP system diagnostic sub-tests are
dependent upon correct fuel level information. The
diagnostic will not run when the tank is less than 15%
or more than 85% full. Be sure to diagnose any Fuel
Level Sensor DTCs first, as they can cause other
DTCs to set.
014RW114

Manifold Absolute Pressure (MAP) Sensor. The
PCM compares the signals from the fuel tank
pressure sensor and the MAP sensor to ensure that a
relative vacuum is maintained the EVAP system.

6E±587
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
055RW004
Non-Electrical Components

Purge/Vacuum Hoses. Made of rubber compounds,
these hoses route the gasoline fumes from their
sources to the canister and from the canister to the
intake air flow.

EVAP Canister. Mounted on a bracket ahead of the
fuel tank, the canister stores fuel vapors until the PCM
determines that engine conditions are right for them
to be removed and burned.

Fuel Tank. The tank has a built-in air space designed
for the collection of gasoline fumes.
060R200081

Vacuum Source. The vacuum source is split between
two ports, one on either side of the throttle body.

Fuel Cap. The fuel cap is designed to be an integral
part of the EVAP system.System Fault Detection
The EVAP leak detection strategy is based on applying
vacuum to the EVAP system and monitoring vacuum
decay. The PCM monitors vacuum level via the fuel tank
pressure sensor. At an appropriate time, the EVAP purge
solenoid and the EVAP vent solenoid are turned ªON,º
allowing the engine vacuum to draw a small vacuum on
the entire evaporative emission system.
After the desired vacuum level has been achieved, the
EVAP purge solenoid is turned ªOFF,º sealing the system.
A leak is detected by monitoring for a decrease in vacuum
level over a given time period, all other variables
remaining constant. A small leak in the system will cause
DTC P0442 to be set.
If the desired vacuum level cannot be achieved in the test
described above, a large leak or a faulty EVAP purge
solenoid is indicated.
Leaks can be caused by the following conditions:

Disconnected or faulty fuel tank pressure sensor

Missing or faulty fuel cap

Disconnected, damaged, pinched, or blocked EVAP
purge line

Disconnected or damaged EVAP vent hose

Disconnected, damaged, pinched, or blocked fuel
tank vapor line

Disconnected or faulty EVAP purge solenoid

Disconnected or faulty EVAP vent solenoid

Open ignition feed circuit to the EVAP vent or purge
solenoid

Damaged EVAP canister

Leaking fuel sender assembly O-ring

Leaking fuel tank or fuel filler neck
A restricted or blocked EVAP vent path is detected by
drawing vacuum into the EVAP system, turning ªOFFº the
EVAP vent solenoid and the EVAP purge solenoid (EVAP
vent solenoid ªOPEN,º EVAP purge Pulse Width
Modulate (PWM) ª0%º) and monitoring the fuel tank
vacuum sensor input. With the EVAP vent solenoid open,
any vacuum in the system should decrease quickly
unless the vent path is blocked. A blockage like this will
set DTC P0446 and can be caused by the following
conditions:

Faulty EVAP vent solenoid (stuck closed)

Plugged, kinked or pinched vent hose

Shorted EVAP vent solenoid driver circuit

Plugged EVAP canister
The PCM supplies a ground to energize the purge
solenoid (purge ªONº). The EVAP purge control is PWM,
or turned ªONº and ªOFF,º several times a second. The
duty cycle (pulse width) is determined by engine
operating conditions including load, throttle position,
coolant temperature and ambient temperature. The duty
cycle is calculated by the PCM and the output is
commanded when the appropriate conditions have been
met.

6E±588
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
The system checks for conditions that cause the EVAP
system to purge continuously by commanding the EVAP
vent solenoid ªONº and the EVAP purge solenoid ªOFFº
(EVAP vent solenoid ªCLOSED,º EVAP purge PWM
ª0%º). If fuel tank vacuum level increases during the test,
a continuous purge flow condition is indicated, which will
set a DTC P1441. This can be cause by the following
conditions:

EVAP purge solenoid leaking

EVAP purge and engine vacuum lines switched at the
EVAP purge solenoid

EVAP purge solenoid driver circuit grounded
Fuel vapor recovery system
060R100095Separator attaches after hose evaporative fuel. It
protects EVAP Canister from liquid fuel. It guarantees
EVAP Canister performance. When vibration bounces
fuel level, liquid fuel will accrete to EVAP Canister. It
separates liquid fuel.
General Description (Exhaust Gas
Recirculation (EGR) System)
EGR Purpose
The exhaust gas recirculation (EGR) system is use to
reduce emission levels of oxides of nitrogen (NOx). NOx
emission levels are caused by a high combustion
temperature. The EGR system lowers the NOx emission
levels by decreasing the combustion temperature.
057RW002
Linear EGR Valve
The main element of the system is the linear EGR valve.
The EGR valve feeds small amounts of exhaust gas back
into the combustion chamber. The fuel/air mixture will be
diluted and combustion temperatures reduced.
Linear EGR Control
The PCM monitors the EGR actual positron and adjusts
the pintle position accordingly. The uses information from
the following sensors to control the pintle position:

Engine coolant temperature (ECT) sensor.

Throttle position (TP) sensor.

Mass air flow (MAF) sensor.
Linear EGR Valve Operation and Results
of Incorrect Operation
The linear EGR valve is designed to accurately supply
EGR to the engine independent of intake manifold
vacuum. The valve controls EGR flow from the exhaust
to the intake manifold through an orifice with a PCM
controlled pintle. During operation, the PCM controls
pintle position by monitoring the pintle position feedback
signal. The feedback signal can be monitored with a Tech
2 as ªActual EGR Pos.º ªActual EGR Pos.º should always
be near the commanded EGR position (ºDesired EGR
Pos.º). If a problem with the EGR system will not allow the
PCM to control the pintle position properly, DTC P1406
will set. The PCM also tests for EGR flow. If incorrect flow
is detected, DTC P0401 will set. If DTCs P0401 and/or
P1406 are set, refer to the DTC charts.
The linear EGR valve is usually activated under the
following conditions:

Warm engine operation.

Above-idle speed.
Too much EGR flow at idle, cruise or cold operation may
cause any of the following conditions to occur:

Engine stalls after a cold start.

Engine stalls at idle after deceleration.