air condition ISUZU TROOPER 1995 Workshop Manual

6E2-112 DRIVEABILITY AND EMISSIONS
CHART C-1E
POWER STEERING PRESSURE (PSP) SWITCH DIAGNOSIS
Circuit Description:
The Power Steering Pressure
(PSP) Switch is normally open to ground, and GRNIYEL wire will be near the battery
positive
voltage.
Turning the steering wheel increases power steering oil pressure and its load on an idling engine. The pressure
switch
will close before the load can cause an idle problem.
Closing
the switch causes GRN/YEL wire to read less than 1 volt. The Engine Control Module (ECM) will increase
the
idle air rate and disengage the air conditioning relay.
•
A pressure switch that will not close, or an open GRNIYEL wire, may cause the engine to stop, when power
steering loads are high.
• A switch that will not open or a GRNIYEL wire shorted to ground, may affect idle quality and will cause the air
conditioning
relay to be de-energized.
Test Description:
Numbers
below refer to circled numbers on the diagnostic chart.
CD Different makes of "Scan tools" may display the state of this switch in different ways. Refer to "Scan tool"
operator's manual to determine how this input is indicated.
® Checks to determine if GRNIYEL wire is shorted to ground.
@ This should simulate a closed switch.
POWER STEERING PRESSURE SWITCH ENGINE
CONTROL
MODULE(ECM)
I SIGNAL
r
BLU ---(~ BLU --+8 .. •f---BLU --{~ GRN/YEL ~ ~ B +
(LOCATED IN THE POWER
STEERING PUMP HIGH PASSENGERS CHASSIS PRESSURE LINE)
SIDE GROUND
FENDER
Fig. 6E2-65
•

6E2-116 DRIVEABILITY AND EMISSIONS
SECTION C-2
FUEL METERING SYSTEM
CONTENTS
General Description ...................... 6E2-116
Purpose ............................ 6E2-116
Modes of Operation .................... 6E2-117
Starting Mode ...................... 6E2-117
Clear Flood Mode .................... 6E2-117
RunMode ......................... 6E2-117
"Open Loop" ....................... 6E2-117
"Closed Loop" ...................... 6E2-117
Acceleration Mode ................... 6E2-117
Deceleration Mode ................... 6E2-117
Battery Positive Voltage Correction Mode ... 6E2-117
Fuel Cutoff Mode .................... 6E2-117
Fuel Metering System Components ........... 6E2-118
Fuel Supply System .................... 6E2-118
Fuel Pump Electrical Circuit ............... 6E2-118
Fuel Rail Assembly ..................... 6E2-118
Fuel Injectors ......................... 6E2-119
Fuel Injector Driver Operation ............. 6E2-119
Fuel Pressure Control Valve Assembly ....... 6E2-119
Throttle Body (TB) Assembly .............. 6E2-120
Idle Air Control (lAC) Valve .............. 6E2-120
Throttle Position (TP) Sensor ............ 6E2-121
Induction Air Control Plate System ......... 6E2-121
Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-121
Fuel Metering System . .

. . . . . . . . . . . . . . . . 6E2-121
Fuel System Pressure Test ............... 6E2-121
Idle Air Control (lAC) Valve . .

. . . . . . . . . . . . . 6E2-121
Induction Air Control Plate System ......... 6E2-122
On-Vehicle Service ...................... 6E2-122
Fuel Pump Relay . . . . . . . . . . . . . . . . . . . . . . 6E2-122
Multipart Fuel Injection Components . . . . . . . . 6E2-122 Fuel Pressure Relief Procedure . . . . . . . . . . 6E2-122
Fuel Rail Assembly . . . . . . . . . . . . . . . . . . . . 6E2-122
Unit Repair ............................ 6E2-123
Fuel Injector/Rail ...................... 6E2-123
Throttle Body Assembly . . . . . . . . . . . . . . . . . 6E2-124
Throttle Body (TB) . . . . . . . . . . . . . . . . . . . 6E2-125
Throttle Position (TP) Sensor . . . . . . . . . . . . . 6E2-126
Idle Air Control (lAC) Valve ............... 6E2-126
Minimum Throttle Body (TB) Position Check ... 6E2-127
Chart C-2A Injector Balance ................ 6E2-128
Chart C-2C Idle Air Control (lAC) System Check .. 6E2-130
Chart C-2D Induction Air Control Plate
System Check . .
. . . . . . . . . . . . . . . . . . . . . . 6E2-132
GENERAL DESCRIPTION
PURPOSE
The function of the fuel metering system is to deliver
the correct amount of fuel to the engine under all
operating conditions. Fuel is delivered to the engine by
individual fuel injectors mounted in the intake manifold
near each cylinder.
The main control sensor is the heated oxygen sensor,
which is located in the front pipe. The heated oxygen
sensor indicates
to the engine control module the
amount of oxygen in the exhaust gas, and the engine
control module changes the air/fuel ratio to the engine
by
controlling the fuel injectors. The best air/fuel ratio
to minimize exhaust emissions is 14.7 to
1, which
allows the three way 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 (Fig. 6E2-67).
2. Fuel injectors
1. Engine Control Module (ECMl
4. Catalytic converter
3. 0, sensor
Fig. 6E2-67
I
I

MODES OF OPERATION
The Engine Control Module (ECM) uses voltage inputs
from several sensors to determine how much fuel to
give the engine. The fuel is delivered under one of
several conditions, called "modes". All the modes are
controlled by the ECM and are described below.
Starting Mode
When the ignition is first turned "ON", the ECM turns
"ON" the fuel pump relay for two seconds, and the fuel
pump builds up pressure. The ECM also checks the
Engine
Coolant Temperature (ECT) sensor and the
Throttle Position Sensor, and the determines the
proper
air/fuel ratio for starting. This ranges from 1.5:1
-36·c (-33.F) to 14.7:1, at 94•c (201.F) ECT.
The ECM controls the amount of fuel delivered in the
starting mode by changing
how long the injector is
turned
"ON" and "OFF". The is done by "Pulsing" the
injectors
for very short times.
Clear Flood Mode
If the engine floods, it may be cleared by pushing the
accelerator pedal down all the way. The ECM then will
fixed air/fuel ratio 16.5:1. The ECM holds this injector
rate
as long as the throttle stays wide open. If the
throttle position becomes less than approximately
70%, the ECM returns to the starting mode.
Run Mode
The run mode has two conditions called "Open Loop"
and "Closed Loop"
"Open Loop"
When the engine is first started, and it is above 500
Rovolution Per Minute (rpm), the system goes into
"Open Loop" operation. IN "Open Loop," the ECM
ignores the signal from the heated oxygen sensor
(H02S), and calculates the air/fuel ratio based on
inputs
from the ECT sensor and manifold absolute
pressure sensors.
The system stays in
"Open Loop" until the following
conditions are met:
1. The H02S has varying voltage output, showing
that
it is hot enough to operate properly. (This
depends on temperature.)
2. The ECT sensor is above a specified temperature.
3. A specific amount of time has elapsed after
starting the engine.
"Closed Loop"
The specific values for the above conditions vary with
different engines, and are stored in the ECM. When
these conditions are met, the system goes into
"Closed
Loop"
operation. In "Closed Loop", the ECM calculates
the air/fuel ratio (injector on-time) based on the signal
from the H02S. This allows the air/fuel ratio to stay
very close to 14.7:1.
DRIVEABILITV AND EMISSIONS 6E2-117
Acceleration Mode
The ECM responds to rapid changes in throttle position
and air
flow, and provides extra fuel.
Deceleration Mode
The ECM responds to changes in throttle position and
air
flow, and reduces the amount of fuel. When
deceleration is very fast, the ECM can cut off fuel
completely
for short periods.
Battery Positive Voltage Correction Mode
When battery positive voltage is low, the ECM can
compensate
for a weak spark delivered by the ignition
control module by:
• Increasing injector pulse width.
• Increasing the idle rpm.
• Increasing ignition dwell time.
Fuel Cutoff Mode
The fuel injectors are shut "OFF" if engine speed
"exceed" 6880 rpm (DOHC) or6800 rpm (SOHC). This is
to prevent damage to engine. When engine speed is
below 6880 rpm (DOHC) or 6800 rpm (SOHC), the fuel
injectors are again pulsed at a normal mode.

6E2-118 DRIVEABILITV AND EMISSIONS
FUEL METERING SYSTEM COMPONENTS
The fuel metering system (Fig. 6E2-68) consists of the
following components:
• Fuel supply components (fuel tank, pump and
lines).
• Fuel
pump electrical circuit.
• Fuel rail assembly, including:
-Fuel pressure control valve
• Throttle
body assembly, including:
-Idle Air Control valve
-Throttle Position Sensor
engine
sensors
• Fuel • :pump : ........
Fuel tank
Fig. 6E2-68
FUEL SUPPL V SYSTEM
The fuel supply is stored in the fuel tank. An electric
fuel
pump, located in the fuel tank with the gage
sending unit, pumps
fuel through an in-line fuel filter to
the
fuel rail assembly. The pump is designed to
provide
fuel at a pressure above the pressure needed
by the injectors. A fuel pressure control valve, an
integral part of the fuel rail assembly, keeps fuel
available
to the injectors at a controlled pressure.
Unused
fuel is returned to the fuel tank by a separate
line. See ENGINE FUEL (SECTION 6C) for replacement
procedures covering the fuel tank, fuel pump, in-line
filter
and fuel lines.
FUEL PUMP ELECTRICAL CIRCUIT
When the key is first turned "ON" without the engine
running, Engine
Control Module (ECM) will turn the fuel
pump relay "ON" for two seconds. This builds up the
fuel pressure quickly. lfthe engine is not started within
two seconds, the ECM will shut the fuel pump "OFF"
and wait until the engine starts. As soon as the engine
is cranked, the
ECM will turn the relay "ON" and run the
fuel pump.
An inoperative
fuel pump would cause a no start
condition. A
fuel pump which does not provide
enough pressure can
result in poor performance,
(refer to CHARTs A-5 and A-7).
FUEL RAIL ASSEMBL V
The fuel rail assembly (Fig. 6E2-69) is mounted to the
Inlet manifold, and performs several functions: It
positions the injectors in the cylinder head, it
distributes fuel evenly to the injectors, and it integrates
the
fuel pressure control valve into the fuel metering
system.
Fuel flow within the rail is shown in Fig. 6E2-
70.
Fig. 6E2-69
Fig. 6E2-70

6E2 120 DRIVEABILITY AND EMISSIONS
THROTTLE BODY (TB) ASSEMBLY
The Throttle Body (TB) assembly is attached to the
intake manifold air
plenum, and is used to control air
flow into the engine, thereby controlling engine output
(Fig. 6E2-73). The TB within the TB is opened by the
driver through the accelerator controls. During engine
idle, the
TB is almost closed, and air flow control is
handled by the Idle Air Control (lAC) valve, described
below. To prevent
TB icing during cool weather
operation, engine
coolant is directed through a engine
coolant tube, part
of the TB, the engine coolant then
circulates through internal passageways around the
throttle bore and returns via the return engine coolant
tube.
The
TB also provides the location for mounting the
Throttle Position
Sensor. Vacuum ports the located at,
above or
below the throttle body to generate vacuum
signal needed
by various components.
Idle Air Control (lAC) Valve
Engine idle speed is controlled by the Engine Control
Module (ECM) through the Idle Air Control (lAC) valve
mounted on the
TB. The ECM sends voltage pulses to
the lAC motor windings causing the lAC valve pintle to
move "IN" or "OUT" a given distance (a step or count)
for each pulse. The pintle movement controls the
airflow around the TBs, which in turn, controls engine
idle speed.
• The "controlled" or desired idle speed for all
engine operating conditions is programmed into
the
calibration of the ECM. The programmed
engine speeds are based on engine coolant
temperature, park/neutral position switch status,
vehicle speed, battery positive voltage, and air
conditioning pressure (if equipped).
• The ECM "learns" the proper lAC valve positions to
achieve warm, stabilized idle speeds (revolution
per minute), desired
for the various conditions
(Park/Neutral position
or Drive, air conditioning
"ON" or "OFF", if equipped). This information is
stored in
ECM "Keep Alive" memories
(information
is retained after ignition is "OFF"). All
other lAC valve positioning is calculated based on
these
memory values.
As a
result, engine variations due to wear and
variations in
minimum TB position (within limits)
do not affect engine idle speeds. This system
provides correct idle control under
all conditions.
This also means
that disconnecting power to the
ECM can result in incorrect idle control or
necessity to partially depress the accelerator
pedal
when starting until the ECM relearns idle
control. Refer to note regarding clearing
memory
in "ECM and Sensors," Section "6E2-C1 ".
•
Engine idle speed is a function of total airflow into
the engine based on
lAC valve pintle position plus
TB opening plus calibrated vacuum loss through
accessories.
• The minimum TB position is set at the factory with
a stop screw. This setting allows enough air flow
by the TB to cause the lAC valve pintle to be
positioned a calibrated
number of steps (counts),
from the seat, during "controlled" idle operation.
The
minimum TB position setting on this engine
should not be considered the
"minimum idle
speed", as on other fuel injected engines. The
throttle stop
screw is covered with a plug at the
factory
following adjustment.
U7 CAUTION:
VI Do not attempt to remove the protective cap and
readjust the stop screw before
reviewi~g t~e
"Minimum TB Position Check", later m th1s
section. Misadjustment may result in damage to
the lAC valve or TB.
Fig. 6E2-73
2. Throttle body assembly
3. Throttle position sensor (TPS)
• The ECM normally resets the lAC valve pintle
position once during each ignition cycle,
when
vehicle speed increases above 35 miles per hour
on moderate acceleration. During the reset, the
ECM commands the lAC valve pintle to retract
completely, then move
"IN" to the seated position
(to establish the zero
count position), and then
back
out to the desired position. If, after the reset,
the
ECM is able to control the idle speed within the
calibrated count range, the
lAC valve will not be
reset again until the ignition has been turned
"OFF", the engine restarted and the car then
driven above 35 mile per hour.
If the ECM is not
able to control idle speed within the calibrated
count range after the first reset, the
ECM assumes
the
lAC valve pintle position is "lost", and enables
another reset
to occur. This will continue until the
pintle position is relearned.
• If the lAC valve is suspected as being the cause of
improper idle speed, perform a functional check of
the lAC valve (CHART C-2C) as described later in
this section.
-----------------------------'
•

Throttle Position (TP) Sensor
The Throttle Position (TP) Sensor is mounted on the
side
of the throttle body opposite the throttle lever
assembly.
Its function is to sense the current throttle
body position and relay that information to the ECM.
Knowledge ofTP is needed by the ECM to generate the
proper injector pulse width.
If the TP sensor senses a
Wide
Open Throttle, a voltage signal indicating this
condition is transmitted to the
ECM. The ECM will
widen the injector pulse, or increase the repetition rate,
permitting increased fuel
flow to each for the six fuel
injectors located in the fuel fail. As the throttle shaft
rotates in response to
movement of the accelerator
pedal (opening
or closing of the throttle body), the
throttle shaft transmits throttle
movement to the TP
sensor. A potentiometer (variable resistor) within the
TP sensor assembly creates a voltage that varies in
response to
TP. By applying a reference voltage (+5
VDC) to the TP sensor input, a varying voltage
(reflecting
TP) is available at the TP sensor output. The
voltage
output from the TP sensor is sent to the ECM
for use in determining current TP.
For further information ofTP sensor, refer to "ECM and
Sensors", Section
"6E2-C1 ". The TP sensor is an auto
zeroing type and cannot
be adjusted.
DRIVEABILITY AND EMISSIONS 6E2-121
INDUCTION AIR CONTROL PLATE
SYSTEM (DOHC) (Fig. 6E2-74)
This system consists of the Induction Air control plate
valve mounted in the common chamber
duct and a
vacuum operated diaphragm
which moves the Induction Air
Control Plate linkage. The vacuum to the diaphragm is
turned
"ON" or "OFF" by a vacuum switching solenoid
which is electrically operated by the
ECM.
Refer to CHART C-20 for diagnosing the Induction air
control plate system.
Manifold vaccum
1
Vacuum actuator
Induction air control plate valve
(noma! open)
Fig. 6E2-74
Engine control module (ECM)
Ignition switch
Canister, EGR, A.I.R. solenoids
DIAGNOSIS
FUEL METERING SYSTEM
Some failures of this system will result in the symptom,
"Engine Cranks But Will Not Run". If this condition
exists, see CHART A-3. This chart will determine
if the
problem is caused by the ignition system,
ECM or fuel
pump circuit.
If it's determined to be a fuel problem.
CHART A-5
or A-7 will be used. This includes the
injectors, fuel pressure control valve, fuel
pump and
fuel pump relay. The fuel system
wiring schematic
diagram is covered on the facing page
of CHART A-5.
If a malfunction occurs in the fuel control system, it
usually results in either a rich or lean Heated Oxygen
Sensor (H02S) signal condition. This condition is
sensed by the
H02S and the ECM will change the fuel
calculation (injector pulse width) based on
H02S input.
The change made to the fuel calculation will be
indicated
by a change in the block learn values which
can be displayed on a
"Scan tool". The ideal block learn
values are around 128 counts.
If the H02S senses a
lean condition, the
ECM will add fuel, resulting in a
block learn value above 128 counts.
If the H02S senses
a rich condition, the
ECM will subtract fuel, resulting in
a block learn value below 128 counts.
Block learn values can vary greatly, depending on
temperature, altitude and individual engine
tolerances. The programmed range for block learn
values is
58 to 198. Values within this range indicate
the system is in
"control". If a system is operating near
the extremes
of the block learn range during normal vehicle
operation, and there is a driveability complaint,
the fuel metering system should be checked. Refer to
the diagnostic trouble code
45 chart on the facing page
for potential causes of a rich condition (low block learn
values). Refer to the diagnostic trouble code 44 chart
facing page
for potential causes of a lean condition
(high block learn values).
If a driveability symptom
exists, also refer to the particular symptom in
"Symptoms", Section "6E2-B" for additional items to
check.
FUEL SYSTEM PRESSURE TEST
A fuel system pressure test procedure is included in
CHART A-7 under
"Fuel System Diagnosis" in "Engine
Components/Wiring Diagrams/Diagnostic
Charts",
Section "6E2-A" diagnostic charts.
IDLE AIR CONTROL (lAC) VALVE
A "Scan tool" will display Idle Air Control (lAC) valve
position in
"Counts" or steps. "0" steps indicates the
ECM is commanding the lAC valve to be driven all the
way in, to a fully seated position. This condition is
usually caused by a vacuum leak.
The higher the number
of counts, the more air is being
allowed to pass the
lAC valve. A functional check of the
lAC valve system (CHART C-2C) is provided in this
section. Refer to
"Refer, Unstable, or Incorrect Idle,
Stalling"
in "Symptoms", Section "6E2-B" for other
possibilities
for the cause of idle problems.

1~1 Measure (If Installing a New Idle Air
Control (lAC) Valve) (Fig. 6E2-82)
• Distance between tip of idle air control (lAC)
valve pintle and mounting flange.
-
If greater than 28 mm, finger pressure to
slowly retract the pintle. The force required
to retract the pintle
of a new valve will not
cause damage to the valve.
Fig. 6E2-82
E) INSTALLATION
3. lAC valve assembly
2. lAC valve attaching screw
1. lAC valve electrical connector
MINIMUM THROTTLE BODY (TB)
POSITION CHECK
The minimum throttle body (TB) position (throttle stop
screw) adjustment
for the 3.2L should not be
considered the
"minimum idle speed", as on other fuel
injected engines. Low internal friction and provision
for slight production variations and various operation
altitudes resulted in a calibrated
minimum TB position
which is too
low to allow most engines to idle. The
adjustment is preset at the factory and no further
adjustment should be necessary.
If there is a complaint of high idle speed, vacuum leaks
should be considered the
most likely cause. Because
the Engine
Control Module (ECM) "learns" Idle lAC, it is
even less likely
that a stalling complaint would be due
to
an incorrect minimum TB position. In either case,
the
"Symptoms," Section "6E2-B" and lAC valve check
CHART C-2C should be referred to.
If it is determined that the minimum TB position is
suspect,
be sure lAC valve is not "lost'' (not actually at
the location indicated by current
lAC "counts"). The
lAC valve could be "lost" if ECM power has been
interrupted
with the ignition "ON", or the lAC valve has
been disconnected
with the engine running since the
last reset,
as described previously in this section in the
"lAC Valve Assembly" general description.
DRIVEABILITY AND EMISSIONS 6E2-127
The minimum TB position may be checked using the
following procedure.
1. Block drive wheels, and apply parking brake.
2. Connect "Scan tool" to the data link connector.
3. Start engine and allow to reach operating
temperature (about
go•q and "Closed Loop".
4. A/T-shift to DRIVE ("D") and then back to neutral
("N").
5. Select power steering pressure switch input on
"Scan tool". With air conditioning and all electrical
accessories
"OFF", transmission in natural, "Scan
tool" should read "OFF" or "NORMAL". (If not,
refer to
CHART C-1 E to diagnose and repair faulty
power steering pressure switch circuit before
proceeding).
Allow idle to stabilize.
6. Select lAC valve display on "Scan tool", and read
lAC valve counts. If between 5-45 counts, the
minimum
TB position adjustment is acceptable. It
is important to allow idle speed to stabilize to
assure correct counts are determined.
If counts in step 6 are too low, check for intake air
(vacuum) leaks at hoses,
TB and intake manifold or
damaged throttle lever and correct as necessary.
Also, refer to
CHART C-2C facing page "Diagnostic
Aids". If no vacuum leaks or other cause of
excessive air into the intake are found, it may be
necessary
to replace the TB to correct the low idle
speed problem. Refer to
"TB Replacement" in this
section.
If counts in Step 6 are too high, check for damaged
throttle lever or airflow restriction by the
TB. If no
problem is evident, remove inlet air
duct at the TB,
and
clean residue from inside of TB bore and from
edges of TB using carburetor cleaner and a shop
towel. (Do Not use a cleaner that contains methyl
ethyl ketone.
It is an extremely strong solvent, and
not necessary for this type of deposit). Re-check
"Scan tool" lAC valve counts, per the preceding
procedure.
If counts are still too high it may be necessary to
replace the
lAC valve or the TB assembly, If no
vacuum leaks are indicated
or engine loads are
present.
Minimum Throttle Body (TB) Position
(Non-Adjustable)
\fl CAUTION:
VI • It is extremely unlikely that this adjustment will
ever be necessary on a TB that has not been
tampered
with after production! If idle
revolution per minute is low, you may need
to
replace the TB to correct the low idle speed.

DRIVEABILITY AND EMISSIONS 6E2-131
CHART C-2C
IDLE AIR CONTROL (lAC) SYSTEM CHECK
CD • IGNITION "OFF", CONNECT IDLE AIR CONTROL (lAC) DRIVER* TO lAC VALVE. • SET PARKING BRAKE, BLOCK WHEELS, AIR CONDITIONING "OFF".
• IDLE ENGINE IN PARK (A/T) OR NEUTRAL (MIT). • INSTALL "SCAN TOOL" AND DISPLAY REVOLUTION PER MINUTE (RPM). • WITH lAC DRIVER, EXTEND AND RETRACT lAC VALVE. • ENGINE SPEED SHOULD DECREASE AND INCREASE AS lAC IS CYCLED.
I
1 I • RPM CHANGES I NO RPM CHANGE I
I I • RPM SHOULD CHANGE SMOOTHLY
WITH EACH • CHECK lAC PASSAGES.
I FLASH OF THE lAC DRIVER LIGHT FROM 700 RPM • IF OK, REPLACE lAC.
TO ABOUT 1500 RPM. DOES IT?
I
~ cf
• INSTALL APPROPRIATE lAC NODE LIGHT* IN • CHECK lAC PASSAGES.
l ENGINE CONTROL MODULE HARNESS. • IF OK, REPLACE lAC. ®
• CYCLE lAC
DRIVER AND NODE LIGHTS.
• BOTH LIGHTS SHOULD CYCLE RED AND GREEN BUT NEVER "OFF" AS RPM IS CHANGED OVER
ITS RANGE. DO THEY?
I
cf ~ IF CIRCUIT(S) DID NOT TEST GREEN AND RED, CHECK •
USING THE OTHER CONNECTOR ON THE lAC
FOR: DRIVER
PIGTAIL, CHECK RESISTANCE
•
FAULTY CONNECTOR TERMINAL CONTACTS. ACROSS
lAC COILS.
• OPEN CIRCUITS INCLUDING CONNECTIONS. •
SHOULD BE 40 TO 80 OHMS BETWEEN lAC
• CIRCUITS SHORTED TO GROUND OR VOLTAGE. TERMINALS "A" TO "B" AND "C" TO "D".
• FAULTY ENGINE CONTROL MODULE CONNECTION I OR ENGINE CONTROL MODULE.
~
l REPAIR AS NECESSARY AND RETEST. l NOT OK I .
_l
• CHECK RESISTANCE BETWEEN lAC I REPLACE lAC VALVE I TERMINALS "B" AND "C" AND "A" AND RETEST. AND "D". • SHOULD BE INFINITE.
I
~
l
I NOT OK I
]
AC DRIVER AND NODE LIGHT REQUIRED. * I J lAC VALVE AND CIRCUIT OK. I REPLACE lAC VALVE J 37027 FROM KENT-MOORE, INC. REFER TO "DIAGNOSTIC AIDS" ON AND RETEST. FACING~
~ CLEAR DIAGNOSTIC TROUBLE CODES AND CONFIRM "CLOSED LOOP" OPERATION AND NORMAL "CHECK ENGINE" MALFUNCTION
INDICATOR LAMP OPERATION.
------

6E2-134 DRIVEABILITV AND EMISSIONS
SECTION C-3
EVAPORATIVE EMISSION (EVAP) CONTROL SYSTEM
(ELECTRONICALL V CONTROLLED)
CONTENTS
General Description ...................... 6E2-134
Purpose ............................ 6E2-134
Vapor Canister ........................ 6E2-134
Evaporative Emission (EVAP) Control System .. 6E2-134 Results of Incorrect Operation ............. 6E2-135
Diagnosis ............................. 6E2-135
Visual Check of Canister ................. 6E2-135
On-Vehicle service . . . . . . . . . . . . . . . . . . . . . . 6E2-135
Fuel Vapor Canister . . . . . . . . . . . . . . . . . . . . 6E2-135
Canister Hoses . . . . . . . . . . . . . . . . . . . . . . . 6E2-135
Chart C-3 Evaporate Emission Canister
Purge Valve . . . . . . . . . . . . . . . . . . . . . . . . . 6E2-136
GENERAL DESCRIPTION
PURPOSE
The basic Evaporative Emission (EVAP) Control
System used on
all vehicles is the charcoal canister
storage method. This method transfers fuel
vapor
from the fuel tank to an activated carbon (charcoal)
storage device (canister)
to hold the vapors when the
vehicle
is not operating. When the engine is running,
the fuel
vapor is purged from the carbon element by
intake air flow and consumed in the normal
combustion process.
VAPOR CANISTER
Gasoline vapors from the fuel tank flow into the tube
labeled tank.
Any liquid fuel goes into a reservoir in the
bottom of the canister to protect the integrity of the
carbon bed above (Fig 6E2-86). These vapors are
absorbed into the carbon. The canister is purged
when
the engine is running or commanded by Engine
Control Module (ECM).
Ambient air is allowed into the
canister through the air tube in the top. The air mixes
with the vapor and the mixture is drawn into the intake
manifold.
EVAPORATIVE EMISSION (EVAP)
CONTROL SYSTEM
The solenoid used with this canister uses Vacuum
Switch Valve to control purge. The ECM opens and
closes the solenoid to control purge.
The
ECM operates a Normally Closed (N/C) solenoid
valve
which controls the vacuum to purge the charcoal
canister. Under cold engine
or idle conditions, the
solenoid is
not energized by the ECM, which blocks
vacuum
to purge the canister. The
ECM energizes
the solenoid valve and allows
purge when:
• Engine is warm above sg·c (156.F).
• After the engine has been running a specified
time.
4.
1. Vapor from Fuel Tank 4. Carbon
2. Evaporate Emission
Canister Purge
Vacuum
3. Canister Body
Fig. 6E2-86
3.
• Throttle position is above 7% throttle position
sensor.
•

6E2-138 DRIVEABILITY AND EMISSIONS
SECTION C4
ELECTRONIC IGNITION (EI) SYSTEM/IGNITION CONTROL (IC)
CONTENTS
General Description . . . . . . . . . . . . . . . . . . . . . 6E2-138
Purpose
............................ 6E2-138
Operation
........................... 6E2-138
Results of Incorrect Operation . . . . . . . . . . . 6E2-139
How diagnostic trouble code (DTC) 42 is
Determined ........................ 6E2-139
Diagnosis. . . . . . . . . . . . . . . ............. 6E2-139
Diagnostic
trouble code (DTC) 12 . . . . . . . . . 6E2-139
On-Vechicle Service . .

. . . . . . . . . . . . . . . . . . . 6E2-139
Electronic Ignition (EI) Assembly .......... 6E2-139
Crankshaft Position (CKP) Sensor ......... 6E2-140
Ignition Coil
.......................... 6E2-140
Ignition Control
Module (ICM) ............ 6E2-140
Ignition
Timing ....................... 6E2-140
Chart
C-4D-1 Electronic Ignition (EI) misfire
at
Idle .............................. 6E2-142
Chart C-4D-2 Electronic Ignition (EI) misfire
Under Load .......................... 6E2-144
GENERAL DESCRIPTION
PURPOSE
The Electronic Ignition (EI) system controls fuel
combustion by providing a spark to ignite the
compressed
air/fuel mixture at the correct time. To
provide improved engine performance,
fuel economy,
and
control of exhaust emissions, the Engine Control
Module
(ECM) controls spark advance timing with the
Ignition Control (IC) system.
OPERATION
The "EI" is a "waste spark" system in which 2 plugs are
fired
simultaneously from one coil. The spark plugs are
paired
to a coil, so that when both fire, one cylinder is
on the compression stroke and the other is on exhaust.
There is
Iitie resistance across the plug gap on the
exhaust stroke, so the
plug requires very little voltage
to fire, thereby providing the other plug (compression)
with maximum available voltage.
The system uses a magnetic Crankshaft Position (CKP)
sensor which protrudes into the block, within
approximately .050" of the crankshaft reluctor. The
reluctor is a special wheel cast on the crankshaft that
has seven machined
slots, six of which are equally
spaced 60° apart). The seventh slot is spaced 1 oo from
one
of the other slots. As the reluctor rotates with the
crankshaft, the
slots change the magnetic field of the
sensor, causing
an induced voltage pulse.
By counting the time between pulses, the Ignition
Control Module (ICM)
can recognize the pulse of the
seventh
slot (sync pulse). Based on this sync pulse, the
module sends the reference signal to the ECM to
calculate CKP (used to fire coils in correct sequence)
and engine speed.
To
properly control timing, the ECM relies on the
following information:
• Engine load (manifold absolute pressure or
vacuum).
• Atmospheric (barometric) pressure.
• Engine temperature.
• Intake air temperature.
• CKP
• Engine speed (revolution per minute).
The ignition
control system consisits of the "EI"
assembly (coils, module,
and CKP sensor), ECM and
connecting wires. These circuits
perform the following
functions:
• "EI" reference
The CKP sensor sends a signal to the ICM which
generates a reference
pulse which is sent to the
ECM. The ECM uses this signal to calculate CKP
and engine speed (also used to trigger the
injector).
• Reference ground (GND)
This wire is GNd through the module and makes
sure the GNd circuit has no
voltage drop between
the
ICM and the ECM, which if open, could affect
performance.
• Bypass
At about 400 revolution per minute, the ECM
applies 5 volts to this circuit to switch spark timing
control from the ICM to the ECM. An open or
grounded bypass circuit
will set a diagnostic
trouble code 42 and the engine will run at base
timing,
plus a small amount of advance built into
the
ICM.
• IGNITION CONTROL (IC)
The ECM uses this circuit (when bypass voltage is
applied) to trigger the "EI" module. The ECM uses
the
CKP to base its calculation of the amount of
spark advance needed under present engine
conditions.
•