Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1532

6E2–579

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

060R200182

6E2–580

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

Electrical Components
The electrical components that make up the enhanced
EVAP system are:

D

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.

D

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

D

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

D

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.

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D

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.

6E2–581

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

055RW004

Non-Electrical Components

D

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.

D

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.

D

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

060R200081

D

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

D

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:

D

Disconnected or faulty fuel tank pressure sensor

D

Missing or faulty fuel cap

D

Disconnected, damaged, pinched, or blocked EVAP
purge line

D

Disconnected or damaged EVAP vent hose

D

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

D

Disconnected or faulty EVAP purge solenoid

D

Disconnected or faulty EVAP vent solenoid

D

Open ignition feed circuit to the EVAP vent or purge
solenoid

D

Damaged EVAP canister

D

Leaking fuel sender assembly O-ring

D

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:

D

Faulty EVAP vent solenoid (stuck closed)

D

Plugged, kinked or pinched vent hose

D

Shorted EVAP vent solenoid driver circuit

D

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.

6E2–582

RODEO 6VD1 3.2L ENGINE DRIVEABILITY AND EMISSIONS

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:

D

EVAP purge solenoid leaking

D

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

D

EVAP purge solenoid driver circuit grounded

Onboard Vapor Recovery (ORVR) system

060R100095

Separator 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.

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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:

D

Engine coolant temperature (ECT) sensor.

D

Throttle position (TP) sensor.

D

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:

D

Warm engine operation.

D

Above-idle speed.

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

D

Engine stalls after a cold start.

D

Engine stalls at idle after deceleration.