fuel ISUZU TROOPER 1995 Workshop Manual

DRIVEABILITV AND EMISSIONS 6E2-97
ADDITIONAL CHECKS • CHECK: Intake and exhaust manifold for casting
• CHECK: Exhaust gas recirculation (EGR) gasket flash.
for faulty or loose fit.
• CHECK: EGR operation for being open all the time.
Refer to
"EGR," CHART C-7.
DIESELING, RUN-ON
Definition: Engine continues to run after key is turned
"OFF", but runs very roughly. If engine
runs
smoothly, check ignition switch and
adjustment.
PRELIMINARY CHECKS
• Perform the careful visual/physical checks as
described at start of "Symptoms," Section "6E2-
B."
FUEL SYSTEM
• CHECK: Injectors for leaking. Refer to "Fuel
System Diagnosis" CHART A-7.

DRIVEABILITV AND EMISSIONS 6E2-99
SECTION C
COMPONENTS SYSTEMS
CAUTION
When fasteners are removed, always reinstall them at the same location from which they were removed. If a
fastener needs
to be replaced, use the correct part number fastener for that application. If the correct part number
fastener is not available, a fastener of equal size and strength (or stronger) may be used. Fasteners that are not
reused, and those requiring thread locking compound will be called out. The correct torque value must be used
when installing fasteners that require it. If the above conditions are not followed, parts or system damage could
result.
Section
"C" provides information on the following:
• General description of components and sub-systems.
• On-vehicle service.
• Part names and group numbers.
• Diagnostic charts. These include a functional check of the system as well as diagnosis of any problem found in
the functional check.
For locations
of components, wiring diagrams, and engine control module terminal and view, refer to the front of
"Engine Components/Wiring Diagrams/Diagnostic Charts", Section "A".
Refer to the following sections for the appropriate sub-system information:
• C1 Engine Control Module (ECM) and Sensors ................................. Page 6E2-1 00
•
C2 Fuel Metering System .................................................. Page 6E2-116
• C3 Evaporative Emission (EVAP) Control System ............................... Page 6E2-134
• C4 Electronic Ignition (EI) System/Ignition Control (IC) ........................... Page 6E2-138
• C5 Knock Sensor (KS) System .............................................. Page 6E2-146
• C7 Exhaust Gas Recirculation (EGR) System ................................... Page 6E2-151
• C8 Shift Indicator Light (M/T Only) ........................................... Page 6E2-157
• C1 0 Air Conditioning (A/C) Compressor Clutch Control System ..................... Page 6E2-161
• C13 Positive Crankcase Ventilation (PCV) ....................................... Page 6E2-164
DIAGNOSTIC CHARTS
The following diagnostic charts can be found at the end of some of the sections.
• Chart C-1A Park/neutral Position (PNP) Switch Diagnosis (Auto Transmission only) .... Page 6E2-108
• Chart C-1 D Manifold Absolute Pressure (MAP) Output Check ...................... Page 6E2-11 0
•
Chart C-1 E Power Steering Pressure (PSP) Switch Diagnosis ...................... Page 6E2-112
• Chart C-1 F Heated Oxygen Sensor (H02S) Heater Check ......................... Page 6E2-114
• Chart C-2A Injector Balance Test ............................................. Page 6E2-128
• Chart C-2C Idle Air Control (lAC) System Check ................................. Page 6E2-130
• Chart C-2D Induction Air Control System Check (DOHC Only) ...................... Page 6E2-132
• Chart C-3 Evaporate Emission Canister Purge Valve Check ....................... Page 6E2-136
• Chart C-4D-1 Electronic Ignition (EI) Misfire at Idle ................................ Page 6E2-142
• Chart C-4D-2 Electronic Ignition (EI) Misfire Under Load ............................ Page 6E2-144
• Chart C-5 Knock Sensor (KS) System Check .................................. Page 6E2-148
• Chart C-7A Exhaust Gas Recirculation (EGR) System Check ....................... Page 6E2-154
• Chart C-8 Manual Transmission (MIT) Shift Light Check ......................... Page 6E2-158
• Chart C-1 0 Air Conditioning (A/C) System Functional Check ....................... Page 6E2-162

6E2-100 DRIVEABILITY AND EMISSIONS
SECTION C1
ENGINE CONTROL MODULE (ECM) & SENSORS
CONTENTS
General Description ...................... 6E2-1 00
Engine Control Module (ECM) .............. 6E2-100
Engine Control Module (ECM) Function ....... 6E2-1 00
Information Sensors ..................... 6E2-1 01
Engine Coolant Temperature (ECT) Sensor ... 6E2-101
Intake Air Temperature (IAT) Sensor ........ 6E2-101
Heated Oxygen Sensor (H02S) ........... 6E2-101
Throttle Position
(TP) Sensor ............. 6E2-102
Manifold Absolute Pressure (MAP) Sensor ... 6E2-102
Vehicle Speed Sensor (VSS) ............. 6E2-102
Knock Sensor (KS) (DOHC ONLY) .......... 6E2-102
Air Conditioning (A/C) Request Signal ...... 6E2-1 02
Power Steering Pressure (PSP) Switch ...... 6E2-1 02
Park/Neutral Position (PNP) Switch
(Auto only)
........................ 6E2-1 03 Diagnosis ............................. 6E2-1 03
Engine Control Module (ECM) .............. 6E2-1 03
Electrically Erasable Programmable Read
Only Memory ........................ 6E2-1 03
Engine Control Module (ECM) Inputs ....... 6E2-103
Engine Coolant Temperature (ECT) Sensor ... 6E2-1 04
Intake Air Temperature (IAT) Sensor ........ 6E2-1 04
Heated Oxygen Sensor
(H02S) ........... 6E2-1 04
Throttle Position
(TP) Sensor ............. 6E2-1 04
Manifold Absolute Pressure (MAP) Sensor
... 6E2-1 04
Vehicle Speed Sensor (VSS) ............. 6E2-1 04
Air Conditioning (A/C) Request Signal
Power Steering Pressure
(PSP) Switch ..... .
Crankshaft Position
(CKP) Reference Signal ..
Park/Neutral Position (PNP) Switch ....... .
Knock Sensor
(KS) ................... .
On-Vehicle Service ..................... .
Engine Control Module
(ECM) ............ .
Engine Control Module
(ECM) Replacement ..
Engine Coolant Temperature (ECT) Sensor ... .
Intake Air Temperature (IAT) Sensor ........ .
Heated Oxygen Sensor
(H02S) ............ .
Throttle Position
(TP) Sensor ............. .
Manifold Absolute Pressure (MAP) Sensor
.... .
Vehicle Speed Sensor
(VSS) ............. .
Power Steering Pressure
(PSP) Switch ...... .
Park/Neutral Position
(PNP) Switch ......... .
Chart C-1A Park/Neutral Position
(PNP)
Switch Diagnosis .................... .
Chart
C-1 D Manifold Absolute Pressure (MAP)
Output Check
...................... .
Chart
C-1 E Power Steering Pressure (PSP)
Switch Diagnosis .................... .
Chart
C-1 F Heated Oxygen Sensor (H02S)
Heater Check ....................... .
6E2-104
6E2-104
6E2-104
6E2-104
6E2-104
6E2-104
6E2-104
6E2-105
6E2-105
6E2-106
6E2-106
6E2-107
6E2-107
6E2-107
6E2-107
6E2-107
6E2-108
6E2-110
6E2-112
6E2-114
GENERAL DESCRIPTION
ENGINE CONTROL MODULE (ECM)
The Engine Control Module (ECM) (Fig. 6E2-50),
located under the instrument panel, is the control
center of the fuel injection system. If constantly looks
at the information from various sensors, and controls
the systems that affect vehicle performance. The ECM
also performs the diagnostic function of the system. It
can recognize operational problems, alert the driver
through the "Check Engine" malfunction indicator
lamp, and store a diagnostic trouble code or diagnostic
trouble codes which identify the problem areas to aid
the technician in making repairs.
See "Introduction"
Section "6E2" for more information on using the
diagnostic function
of the ECM.
For service, this ECM is replaced as a complete unit.
There are no serviceable parts in the
ECM. The
calibrations are stored in the
ECM in the Electronic
Erasable Programmable Read Only Memory
(EEPROM).
ENGINE CONTROL MODULE (ECM)
FUNCTION
This ECM supplies either 5 to 12 volts to power various
sensors
or switches. This is done through resistances
in the
ECM which are so high in value that a test light
Fig. 6E2-50

will not light when connected to the circuit. In some
cases, even an ordinary shop voltmeter
will not give an
accurate reading because its resistance is
too low.
Therefore, a 10 megohms input impedance digital
voltmeter is required to assure accurate voltage
readings.
The Engine
Control Module (ECM) controls output
circuits such as the fuel injectors, idle air control valve,
air conditioning clutch relay, etc. by controlling the
ground circuit through transistors
or a device called a
"quad-driver".
INFORMATION SENSORS
Engine Coolant Temperature (ECT) Sensor
(Fig. 6E2-51)
The Engine Coolant Temperature (ECT) Sensor is a
thermistor
(a resistor which changes value based on
temperature) mounted in the engine coolant stream.
Low ECT produces a high resistance (1 00,000 ohms at
-40.C/-40.F) while high temperature causes low
resistance (70 ohms at 130.C/266.F).
The ECM supplies a 5-volts signal to the ECT sensor
through a resistor in the
ECM and measures the
voltage. The voltage
will be high when the engine is
cold, and low when the engine is hot.
By measuring the voltage, the
ECM knows the ETC.
ECT affects most systems the ECM controls.
A failure in the
ECT sensor circuit should set a
Diagnostic Trouble Code
(DTC) 14. Remember, these
DTC(s) indicate a failure in the
ETC circuit, so proper
use
of the chart will lead to either repairing a wiring
problem or replacing the sensor, to properly repair a
problem.
1. Engine coolant temperature sensor
2. Harness connector to ECM
3. Locking tab
Fig. 6E2-51
Intake Air Temperature (IAT) Sensor
The Intake Air Temperature (IAT) sensor is a
thermistor, a resistor which changes
value based on
the temperature
of air entering the engine. Low
temperature produces a high resistance
(1 00,000
ohms at -4o·c/-40.F), while high temperature causes
low resistance (70 ohms at 130.C/266.F).
The ECM supplies a 5-volts signal to the sensor through
a resistor in the
ECM and measures the voltage. The
voltage
will be high when the intake air is cold, and low
DRIVEABILITV AND EMISSIONS 6E2-1 01
when the air is hot. By measuring the voltage, the ECM
knows the lAT.
The IAT sensor is also used to control spark timing and
delays exhaust gas recirculation when intake air is
cold.
A failure in the IAT sensor circuit should set a DTC 23.
Heated Oxygen Sensor (H02S) (Fig. 6E2-52)
The Heated Oxygen Sensor (H02S) is mounted in the
exhaust system where
it can monitor the Oxygen (02)
content of the exhaust gas stream. The 02 content in
the exhaust reacts
with the sensor to produce a voltage
output. This voltage ranges
from approximately .1 volt
(high 02-lean mixture) to .9 volt (low 02-rich mixture).
This voltage can
be measured with a digital voltmeter
having at
least 10 megohms input impedance. Use of
standard shop type voltmeters will result in very
inaccurate readings.
By monitoring the voltage
output ofthe H02S, the ECM
will know what fuel mixture command to give to the
injector
(lean mixture-low 02 voltage= rich command,
rich mixture-high
02 voltage= lean command).
The
H02S circuit, if open, should set a DTC 13. A
constant
low voltage in the sensor circuit should set a
DTC 44. While a constant high voltage in the circuit
should set a DTC 45. DTC(s) 44 and 45 could also be set
as a result of fuel system problems. See DTC charts for
conditions that can cause a lean or rich system.
The
H02S works in the same manner as the non-H02S
The exception is that battery positive voltage is
supplied to a heating unit that is part of the sensor
itself. This heater receives voltage
from the ECM's
main
relay circuit.
The heater
helps to heat up the H02S so the ECM can
start
controlling the fuel injection sooner for better fuel
emissions. There are no malfunction DTC(s) to detect if
the heater part of the sensor is working. To check the
heater, refer to "Functional
Check" in this section.
Fig. 6E2-52
~
\W

6E2-1 02 DRIVEABILITV AND EMISSIONS
Throttle Position (TP) Sensor (Fig. 6E2-53)
The Throttle Position (TP) Sensor is a potentiometer
connected to the throttle shaft on the Throttle Body
(TB). The TP sensor electrical circuit consists of a 5
volts supply line (signal line) and a ground line,
provided by the Engine Control Module (ECM).
By
monitoring the voltage on the signal line the ECM
calculates throttle position. As the TB angle is changed
(accelerator pedal moved), the output
of TP sensor
also changes.
At a closed throttle position, the output
of the TP sensor is low (approximately 5volt). As the TB
opens, the output increases so that, at wide-open
throttle, the output voltage
will be between 4 and 5
volts.
The
ECM can determine fuel delivery based on TB
angle (driver demand). A broken or loose TP sensor
can cause intermittent bursts of fuel from the injector,
and
an unstable idle, because the ECM thinks the
throttle is moving. A problem in any
of the TP sensor
circuits should set a diagnostic trouble code
(DTC) 21.
Once a DTC is set, the ECM will use an artificial default
valueforTP sensor. A high idle will result when DTC 21
is set.
See
"On-Vehicle Service" for replacement or
adjustment
of TP sensor.
ECM
~--2. Throttle position
sensor (TPS)
Fig. 6E2-53
Manifold Absolute Pressure (MAP) Sensor (Fig.
6E2-54)
The Manifold Absolute Pressure (MAP) sensor
measures the changes in the intake manifold pressure
which result
from engine load and speed changes, and
converts this to a voltage output.
A closed throttle on engine coast
down would produce
a relatively
low MAP output, while a Wide Open
Throttle would produce a high output. MAP is the
OPPOSITE of what would be measured on a vacuum
gage. When manifold pressure is high, vacuum is low.
The
MAP sensor is also used to measure barometric
pressure under contain conditions, which
allows the
ECM to automatically adjust for different altitudes. The
ECM sends a 5 volts reference signal to the MAP
sensor. As the manifold pressure changes, the
electrical resistance
of the sensor also changes. By
monitoring the sensor output voltage, the ECM knows
the manifold pressure.
A higher pressure,
low vacuum (high voltage) requires
more fuel, while a lower pressure, higher vacuum (low
voltage) requires less
fuel.
A failure in the MAP sensor circuit should set a DTC 33.
Map sensor
Fig. 6E2-54
Vehicle Speed Sensor (VSS)
The Vehicle Speed Sensor, sends a pulsing voltage
signal to the
ECM, which the ECM converts to miles per
hour. This sensor helps to control the
operation
of the idle air control system.
See
ELECTRICAL DIAGNOSIS (SECTION 8A) for more
information.
Knock Sensor (KS) (DOHC only)
The Knock Sensor is mounted in the engine block.
When abnormal engine vibrations (spark knock) are
present, the sensor produces a voltage signal, which is
sent to the knock sensor module.
See
"Knock Sensor System," Section "6E2-C5" for
further information on the knock sensor system.
Air Conditioning (A/C) Request Signal
This signal tells the ECM that the Air Conditioning (A/C)
selector switch is turned
"ON". The ECM uses this to
adjust the idle speed, before turning
"ON" the A/C
clutch.
If this signal is not available to the ECM, the A/C
compressor will be inoperative.
See "A/C Compressor Clutch Control System", Section
"6E2-C1 0" for A/C wiring diagrams and diagnosis of
A/C electrical system.
Power Steering Pressure (PSP) Switch
This switch tells the ECM that the vehicle is in a parking
maneuver. The
ECM uses this information to
compensate
for the additional engine load by moving
the idle air control valve. The
ECM will also turn "OFF"
the A/C clutch when high pressure is detected.
•

6E2-1 04 DRIVEABILITV AND EMISSIONS
Engine Coolant Temperature (ECT) Sensor
A "Scan tool" displays engine temperature in degrees
centigrade. After engine is started, the temperature
should rise steadily to about 90°C then stabilize when
thermostat opens. If the engine has not been run for
several hours (overnight), the engine coolant
temperature (ECT) and intake air temperature (IAT)
readings should be close to each other. A fault in the
ECT sensor circuit should set a diagnostic trouble code
(DTC) 14. The DTC charts also contain a chart to check
for sensor resistance values relative to temperature.
Intake Air Temperature (IAT) Sensor
A "Scan tool" displays temperature of the air entering
the engine and
should read close to ambient air
temperature when engine
is cold, and rise as under
hood temperature increases.
If the engine has not
been run for several hours (overnight), the IAT sensor
temperature and
ECT readings should be close to each
other. A
failure in the IAT sensor circuit should set a
DTC 23. The DTC charts also contain a chart to check
for sensor resistance values relative to temperature.
Heated Oxygen Sensor (H02S)
The "Scan tool" has several positions that will indicate
the state
of the exhaust gases, Oxygen voltage,
integrator, and block learn. See "Scan tool" position
information in
"Introduction", "Driveability and
Emission," in this section.
A
problem in the oxygen sensor circuit, or fuel system,
should set a DTC 13 (open circuit), DTC 44 (lean
indication)/DTC 45 (rich indication). Refer to
applicable chart, if any of these DTC(s) were stored in
memory.
Throttle Position (TP) Sensor
A "Scan tool" displays throttle position in volts. On 3.2L
engine, Throttle position
(TP) sensor voltage should
read below 0.85 volts, with throttle closed and ignition
"ON", or at idle. Voltage should increase at a steady
rate
as throttle is moved toward wide open throttle.
The Engine
Control Module (ECM) has the ability to
auto-zero the TP sensor voltage if it is below about 0.85
volts. This means that any voltage less than 0.85 volts
will
be determined by the ECM to be 0% throttle.
Some
"Scan tools" have the ability to read the throttle
angle and should read 0%, when the throttle is closed.
A failure in the TP sensor or circuit should set a DTC 21.
Manifold Absolute Pressure (MAP) Sensor
"Scan tool" displays manifold pressure in volts. Low
pressure (high vacuum) reads a
low voltage, while a
high pressure
(low vacuum) reads a high voltage. A
failure in the Manifold Absolute Pressure (MAP) sensor
circuit
should set a DTC 33 and using the chart will find
the cause
of the problem. A DTC 33 may be set if a
rough or unstable
idle exists. CHART C-1 D can also be
used
to check MAP sensor.
Vehicle Speed Sensor (VSS)
A "Scan tool" reading should closely match with
speedometer reading with drive wheels turning. A
failure in the vehicle speed sensor circuit should set a
DTC 24.
AIR CONDITIONING (A/C) Request Signal
When air conditioning in "ON", the "Scan tool" should
indicate air conditioning "ON".
See
"Air Conditioning Compressor Clutch Control
System",
Section "6E2-C1 0" for A/C electrical system
diagnosis.
Power Steering Pressure (PSP) Switch
A "Scan tool" should read "OFF" normally, and "ON"
with high pressure. This reading may vary with
different "Scan tools". Refer to CHART C-1 E for power
steering pressure switch diagnosis.
Crankshaft Position (CKP) Reference Signal
The ignition control module sends a signal to the ECM,
which is used to calculate proper spark advance and
fuel delivery. A "Scan tool" will read this signal and is
displayed in revolution per minute.
See "Electronic
Ignition System",
Section "6E2-C-4" for more
information on the ignition system (ignition control).
Park/Neutral Position (PNP) Switch
A "Scan tool" should read park/neutral position when
in park, or neutral, and R-D, L, when in drive or
overdrive. This reading may vary with different makes
of tools. Refer to CHART C-1 A for park/neutral position
switch diagnosis.
Knock Sensor (KS)
A "Scan tool" will indicate when the knock sensor
module signals the ECM that knock is present. See
"Knock
Sensor System," Section "6E2-C5" for further
information on the knock sensor system.
ON-VEHICLE SERVICE
ENGINE CONTROL MODULE (ECM)
The ECM is programmed from the factory and has no replaceable calibration chip.
•

6E2-1 06 DRIVEABILITV AND EMISSIONS
1••1 REMOVAL
\f7 CAUTION:
Y/ Care must be taken when handling Engine
Coolant Temperature (ECT) sensor. Damage to
ECT sensor will affect proper operation of the fuel
injection system.
Preparation: • Negative battery cable.
•
Drain engine coolant system.
1. Inlet manifold assembly
• Refer to "Fuel metering system" section "6E2-
C2"
for removal procedure.
2. Electrical connector
3. ECT sensor
• Remove from rear of engine coolant transfer
tube.
I••IINSTALLATION
3. ECT sensor
• Apply sealer or equivalent to threads only.
•
Tighten the ECT sensor to the specified torque
~~~ Torque N·m (lb·ft) I 30 (22)
2. ECT sensor connector
1. Intake manifold assembly
• Refer to "Fuel metering system" section "6E2-
C2" for installation.
INTAKE AIR TEMPERATURE (IAT)
SENSOR
Fig. 6E2-57
1••1 REMOVAL
Preparation: • Negative battery cable.
1. Wiring connector
• Disconnect connector from Intake Air
Temperature (IAT) sensor.
2. IAT sensor
I••IINSTALLATION
2. IAT sensor
• Apply sealer or equivalent to threads only.
•
Tighten the IAT sensor to the specified torque.
~~~ Torque N·m (lb·ft) 30 (22)
1. Wiring
connector
HEATED OXYGEN SENSOR (H02S)
Fig. 6E2-58
1••1 REMOVAL
'fCAUTION
• The Heated Oxygen Sensor (H02S) uses a
permanently attached pigtail and connector.
This
pigtail should not be removed from the
H02S. Damage or removal of the pigtail or
connector
could affect proper operation of the
H02S.
•
Take care when handling the H02S. The in-line
electrical
connector and louver end must be
kept free
of grease, dirt, or other contaminants.
Also, avoid using cleaning solvents of any type.
Do not drop or roughly handle the H02S.
Preparation: • Battery negative cable.
1. H02S wiring connector
2. H02S
• The H02S may be difficult to remove when
engine temperature is
below 48• (120.).
•
Excessive force may damage threads in
exhaust pipe.
I••IINSTALLATION
2. H02S
• A special anti-seize compound is used on the
H02S threads. The compound consists of a
liquid graphite which will burn away, but the
glass beads will remain, making the sensor
easier
to remove.
•

6E2-11 0 DRIVEABILITY AND EMISSIONS
CHART C-10
MANIFOLD ABSOLUTE PRESSURE (MAP) OUTPUT CHECK
Circuit Description:
Manifold Absolute Pressure (MAP) sensor measures the changes in the intake MAP which result
from engine load
(intake manifold vacuum) and revolution per minute changes; and converts these into a voltage output. The
Engine
Control Module (ECM) sends a 5-volt reference voltage to the MAP sensor. As the MAP changes, the
output voltage of the sensor also changes. By monitoring the sensor output voltage, the ECM knows the MAP. A
lower pressure (low voltage)
output voltage will be about 1 - 2 volts at idle. While higher pressure (high voltage)
output voltage
will be about 4-4.8 at Wide Open Throttle. The MAP sensor is also used, under certain conditions,
to measure barometric pressure,
allowing the ECM to make adjustment for different altitudes. The ECM uses the
MAP sensor
to control fuel delivery and ignition timing.
Test Description:
Numbers
below refer to circled numbers on the diagnostic chart.
\fl CAUTION
'(/ • Be sure to use the same Diagnostic Test Equipment for all measurements.
CD When comparing "Scan tool" readings to a known good vehicle, it is important to compare vehicle that use a
MAP sensor having the same color insert
or having the same "Hot Stamped" number. See figures on facing
page.
® Applying 34 kPa (1 0" hydragyrum) vacuum to the MAP sensor should cause the voltage to be 1.5-2.1 volts
than the voltage at
Step 1. Upon applying vacuum to the sensor, the change in voltage should be
instantaneous. A slow voltage change indicates a faulty sensor.
® Check vacuum hose to sensor for leaking or restriction. Be sure that no other vacuum devices are connected ....-...
the MAP hose. ~
NOTE:
Make sure electrical connector remains securely fastened.
@) Disconnect sensor from bracket and twist sensor by hand (only) to check for intermittent connection. Output
changes greater that
.1 0 volt indicate a bad sensor.
MANIFOLD
ABSOLUTE PRESSURE
SENSOR
TO MANIFOLD
ABSOLUTE PRESSURE
(VACUUM)
HARNESS ENGINE
CONNECTOR
(BLUE) TOTPS
TOECT SENSOR
Fig. 6E2-62
GRY
ENGINE CONTROL
MODULE(ECM)
I---...JVV'--5 VOLT
REF
SENSOR -GROUND
•

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.