Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 886

6E–568

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

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 remove and burned.

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

014RW145

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 “ON,”
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 “OFF,” 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 “OFF” the
EVAP vent solenoid and the EVAP purge solenoid (EVAP
vent solenoid “OPEN,” EVAP purge Pulse Width
Modulate (PWM) “0%”) 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 “ON”). The EVAP purge control is PWM,
or turned “ON” and “OFF,” 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.
The system checks for conditions that cause the EVAP
system to purge continuously by commanding the EVAP
vent solenoid “ON” and the EVAP purge solenoid “OFF”
(EVAP vent solenoid “CLOSED,” EVAP purge PWM
“0%”). 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

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.

6E–569

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

060R200237

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 “Actual EGR Pos.” “Actual EGR Pos.” should always
be near the commanded EGR position (”Desired EGR
Pos.”). 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.

Vehicle surges during cruise.

Rough idle.

DTC P0300 (misfire detected).

Too little or no EGR flow may allow combustion
temperatures to get too high. This could cause:

Spark knock (detonation).

Engine overheating.

Emission test failure.

DTC P0401 (EGR flow test).

Poor fuel economy.

0017

EGR Pintle Position Sensor

The PCM monitors the EGR valve pintle position input to
endure that the valve responds properly to commands
from the PCM and to detect a fault if the pintle position
sensor and control circuits are open or shorted. If the
PCM detects a pintle position signal voltage outside the
normal range of the pintle position sensor, or a signal
voltage that is not within a tolerance considered
acceptable for proper EGR system operation, the PCM
will set DTC P1406.

General Description (Positive
Crankcase Ventilation (PCV) System)

Crankcase Ventilation System Purpose

The crankcase ventilation system is use to consume
crankcase vapors in the combustion process instead of
venting them to the atmosphere. Fresh air from the
throttle body is supplied to the crankcase and mixed with
blow-by gases. This mixture is then passed through the
positive crankcase ventilation (PCV) valve into the
common chamber.

Crankcase Ventilation System Operation

The primary control is through the positive crankcase
ventilation (PCV) valve. The PCV valve meters the flow at
a rate that depends on the intake vacuum. The PCV valve
restricts the flow when the inlet vacuum is highest. In

6E–570

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

addition, the PCV valve can seal the common chamber
off in case of sudden high pressure in the crankcase.

060R200198

While the engine is running, exhaust fuses and small
amounts of the fuel/air mixture escape past the piston
rings and enter the crankcase. These gases are mixed
with clean air entering through a tube from the air intake
duct.

060R200063

During normal, part-throttle operation, the system is
designed to allow crankcase gases to flow through the
PCV valve into the throttle body to be consumed by
normal combustion.
A plugged valve or PCV hose may cause the following
conditions:

Rough idle.

Stalling of slow idle speed.

Oil leaks.

Sludge in the engine.

A leaking PCV hose would cause:

Rough idle.

Stalling.

High idle speed.

6E–571

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Special Tools

ILLUSTRATION

TOOL NO.

TOOL NAME

J 39200

High Impedance

Multimeter (Digital

Voltmeter – DVM)

(1) PCMCIA Card

(2) RS232 Loop Back

Connector

(3) SAE 16/19 Adapter

(4) DLC Cable

(5) TECH–2

J 34142-B

Unpowered Test Light

Connector Test Adapter

Kit J 35616-A/BT-8637

J 26792/BT-7220-1

Spark Tester

J 34730-E

Port Fuel Injection

Diagnostic Kit

ILLUSTRATION

TOOL NO.

TOOL NAME

J 37027-A

IAC Motor Analyzer

J 23738-A

Vacuum Pump with

Gauge

BT-8515/8515V

Exhaust Back Pressure

Tester

J 39194-B

Heated Oxygen Sensor

Wrench

J 35689-A

Terminal Remover

J 28742-A

Weather Pack II

Terminal Remover

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