Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Service manual - part 1344

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RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Damage during re–gapping can happen if the
gapping tool is pushed against the center electrode or
the insulator around it, causing the insulator to crack.
When re–gapping a spark plug, make the adjustment
by bending only the ground side terminal, keeping the
tool clear of other parts.

”Heat shock” breakage in the lower insulator tip
generally occurs during several engine operating
conditions (high speeds or heavy loading) and may be
caused by over–advanced timing or low grade fuels.
Heat shock refers to a rapid increase in the tip
temperature that causes the insulator material to
crack.

Spark plugs with less than the recommended amount of
service can sometimes be cleaned and re–gapped, then
returned to service. However, if there is any doubt about
the serviceability of a spark plug, replace it. Spark plugs
with cracked or broken insulators should always be
replaced.

A/C CLUTCH DIAGNOSIS

A/C Clutch Circuit Operation

A 12–volt signal is supplied to the A/C request input of the
PCM when the A/C is selected through the A/C control
switch.
The A/C compressor clutch relay is controlled through the
PCM. This allows the PCM to modify the idle air control
position prior to the A/C clutch engagement for better idle
quality. If the engine operating conditions are within their
specified calibrated acceptable ranges, the PCM will
enable the A/C compressor relay. This is done by
providing a ground path for the A/C relay coil within the
PCM. When the A/C compressor relay is enabled, battery
voltage is supplied to the compressor clutch coil. The
PCM will enable the A/C compressor clutch whenever the
engine is running and the A/C has been requested. The
PCM will not enable the A/C compressor clutch if any of
the following conditions are met:

The engine speed is greater than 6315 RPM.

The ECT is greater than 119

C (246

F).

The throttle is more than 80% open.

A/C Clutch Circuit Purpose

The A/C compressor operation is controlled by the
powertrain control module (PCM) for the following
reasons:

It improves idle quality during compressor clutch
engagement.

It improves wide open throttle (WOT) performance.

It provides A/C compressor protection from operation
with incorrect refrigerant pressures.

The A/C electrical system consists of the following
components:

1. The A/C control switch.
2. The A/C refrigerant pressure switches.
3. The A/C compressor clutch.
4. The A/C compressor clutch relay.
5. The PCM.

A/C Request Signal

This signal tells the PCM when the A/C mode is selected
at the A/C control switch. The PCM uses this input to
adjust the idle speed before turning on the A/C clutch. The
A/C compressor will be inoperative if this signal is not
available to the PCM.
For A/C wiring diagrams and diagnosis for the A/C
electrical system, refer to A/C Clutch Circuit Diagnosis.

GENERAL DESCRIPTION —
EVAPORATIVE EMISSION (EVAP)
SYSTEM

EVAP Emission Control System Purpose

The basic evaporative emission (EVAP) control system
used on all vehicles is the charcoal canister storage
method. Gasoline vapors from the fuel tank flow into the
canister through the inlet labeled ”TANK.” These vapors
are absorbed into the activated carbon (charcoal) storage
device (canister) in order to hold the vapors when the
vehicle is not operating. The canister is purged by PCM
control when the engine coolant temperature is over 60

(140

F), the IAT reading is over 10

C (50

F), and the

engine has been running. Air is drawn canister through
the air inlet grid. The air mixes with the vapor and the
mixture is drawn into the intake manifold.

EVAP Emission Control System Operation

The EVAP canister purge is controlled by a solenoid valve
that allows the manifold vacuum to purge the canister.
The Powertrain control module (PCM) supplies a ground
to energize the solenoid valve (purge on). The EVAP
purge solenoid control is pulse–width modulated (PWM)
(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. The output is commanded when
the appropriate conditions have been met. These
conditions are:

The engine is fully warmed up.

The engine has been running for a specified time.

The IAT reading is above 10

C (50

F).

A continuous purge condition with no purge
commanded by the PCM willset a DTC P1441.

Poor idle, stalling and Poor driveability can be caused by:

A malfunctioning purge solenoid.

A damaged canister.

Hoses that are split, cracked, or not connected
properly.

Enhanced Evaporative Emission Control
System

The basic purpose of the Enhanced Evaporative
Emissions control system is the same as other EVAP
systems. A charcoal–filled canister captures and stores
gasoline fumes. When the PCM determines that the time
is right, it opens a purge valve which allows engine
vacuum to draw the fumes into the intake manifold. The

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RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

difference between this and other systems is that the
PCM monitors the vacuum and/or pressure in the system
to determine if there is any leakage. If the PCM
determines that the EVAP system is leaking or not
functioning properly, it sets a Diagnostic Trouble Code
(DTC) in the PCM memory.
The enhanced EVAP system is required to detect
evaporative fuel system leaks as small as 0.040 in. (1.0
mm) between the fuel filler cap and purge solenoid. The
system can test the evaporative system integrity by
applying a vacuum signal (ported or manifold) to the fuel
tank to create a small vacuum. The PCM then monitors
the ability of the system to maintain the vacuum. If the
vacuum remains for a specified period of time, there are
no evaporative leaks and a PASS report is sent to the
diagnostic executive. If there is a leak, the system either
will not achieve a vacuum, or a vacuum cannot be
maintained. Usually, a failure can only be detected after a
cold start with a trip of sufficient length and driving
conditions to run the needed tests. The enhanced EVAP
system diagnostic will conduct up to eight specific
sub–tests to detect fault conditions. If the diagnostic fails
a sub–test, the PCM will store a Diagnostic Trouble Code
(DTC) to indicate the type of fault detected.

Electrical Components
The electrical components that make up the enhanced
EVAP system are:
Fuel Tank 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 top of the upper intake manifold
assembly.
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.

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.
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 in the EVAP system.

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.
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

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RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

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 caused 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 used 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.

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 position and adjusts
the pintle position accordingly. The PCM uses information
from the following sensors to control the pintle position:

Engine coolant temperature (ECT) sensor.

Throttle position (TP) 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.”). The PCM also tests for EGR flow.
If incorrect flow is detected, DTC P0401 will set. If DTC
P0401 is 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 Insufficient detected).

Poor fuel economy.

0017

EGR Pintle Position Sensor

The PCM monitors the EGR valve pintle position input to
ensure 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

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RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

voltage that is not within a tolerance considered
acceptable for proper EGR system operation, the PCM
will set DTC P0404.

GENERAL DESCRIPTION —
POSITIVE CRANKCASE
VENTILATION (PCV) SYSTEM

Crankcase Ventilation System Purpose

The crankcase ventilation system is used 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) port into the intake
manifold.
While the engine is running, exhaust gases 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.

028RX003

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 or slow idle speed.

Oil leaks.

Sludge in the engine.

A leaking PCV hose would cause:

Rough idle.

Stalling.

High idle speed.

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