engine CHRYSLER VOYAGER 2004 Service Manual

FUEL PUMP
DESCRIPTION
The electric fuel pump is located in and is part of
the fuel pump module. It is a positive displacement,
gerotor type, immersible pump with a permanent
magnet electric motor. The fuel pump module is sus-
pended in fuel in the fuel tank.
OPERATION
The pump draws fuel through a strainer and
pushes it through the motor to the outlet. The pump
contains a check valve. The valve, in the pump out-
let, maintains pump pressure during engine off con-
ditions, for a short while. It is normal for fuel
pressure to drop to zero after cooldown. The fuel
pump relay provides voltage to the fuel pump. The
fuel pump has a maximum deadheaded pressure out-
put of approximately 880 kPa (130 psi). The regula-
tor adjusts fuel system pressure to approximately
400 kpa  34 kpa (58 psi   5 psi).
FUEL PUMP MODULE
DESCRIPTION
The fuel pump module is installed in the top of the
fuel tank (Fig. 9).
The fuel pump module contains the following:
²Electric fuel pump²Fuel pump reservoir
²Inlet strainer
²Fuel pressure regulator
²Fuel gauge sending unit
²Fuel supply line connection
The inlet strainer, fuel pressure regulator
and fuel level sensor are the only serviceable
items. If the fuel pump or electrical wiring har-
ness requires service, replace the fuel pump
module.
The electric fuel pump is located in and is part of
the fuel pump module. It is a positive displacement,
gerotor type, immersible pump with a permanent
magnet electric motor.
OPERATION
The pump draws fuel through a strainer and
pushes it through the motor to the outlet. The pump
contains one check valve. The check valve, in the
pump outlet, maintains pump pressure during engine
off conditions. The fuel pump relay provides voltage
to the fuel pump.
The fuel pump has a maximum deadheaded pres-
sure output of approximately 880 kPa (130 psi). The
regulator adjusts fuel system pressure to approxi-
mately 400  34 kPa (58  5 psi).
FUEL PUMP ELECTRICAL CONTROL
Voltage to operate the electric pump is supplied
through the fuel pump relay. For an electrical opera-
tional description of the fuel pump refer to fuel Pump
RelayÐPCM Output.
ELECTRICAL PUMP REPLACEMENT
The electric fuel pump is not serviceable. If the
fuel pump or electrical wiring harness needs replace-
ment, the complete fuel pump module must be
replaced. Perform the Fuel System Pressure Release
procedure before servicing the fuel pump.
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
SERVICE VEHICLES IN WELL VENTILATED AREAS
AND AVOID IGNITION SOURCES. NEVER SMOKE
WHILE SERVICING THE VEHICLE.
(1) Remove fuel filler cap and perform Fuel Sys-
tem Pressure Release procedure.
(2) Disconnect negative cable from auxiliary
jumper terminal.
(3) Drain fuel tank, refer to the Fuel Tank proce-
dure in the Fuel Delivery section.
(4) Remove fuel tank, refer to the Fuel Tank
removal section.
Fig. 9 Fuel Pump Module
1 - INLET STRAINER
2 - FUEL RESERVOIR
3 - FUEL PRESSURE REGULATOR
4 - FUEL LEVEL SENSOR
5 - FILTER
6 - GROUND STRAPS
14 - 8 FUEL DELIVERYRS

(6) Remove harness from vehicle.
(7) Remove fuel hose quick connect fitting from the
chassis tube.Refer to Fuel Hoses, Clamps and
Quick Connect Fittings in this Section.Place a
shop towel under the connections to absorb any fuel
spilled from the fitting.
WARNING: WRAP A SHOP TOWEL AROUND HOSES
TO CATCH ANY GASOLINE SPILLAGE.
(8) Remove fuel rail attaching bolts.
(9) Remove fuel rail. Be careful not to damage the
injector O-rings upon removal from their ports.
REMOVAL - 3.3/3.8L
(1) Perform fuel system pressure release procedure
before servicing or starting repairs.Refer to
Fuel System Pressure Release Procedure in this sec-
tion.
(2) Disconnect negative cable from battery.
(3) Remove upper intake manifold, refer to the
Engine/Manifolds/Upper Intake for more informa-
tion..
(4) Cover intake manifold with suitable cover
when servicing.
(5) Remove the fuel hose quick connect fitting from
the chassis tube.Refer to Fuel Hoses, Clamps
and Quick Connect Fittings in this Section.
WARNING: WRAP A SHOP TOWEL AROUND HOSES
TO CATCH ANY GASOLINE SPILLAGE.
(6) Remove the fuel rail attaching bolts (Fig. 13).
(7) Remove fuel rail. Be careful not to damage the
injector O-rings upon removal from their ports.
INSTALLATION
INSTALLATION - 2.4L
(1) Ensure injector holes are clean. Replace
O-rings if damaged.
(2) Lubricate injector O-rings with a drop of clean
engine oil to ease installation.
(3) Put the tip of each injector into their ports.
Push the assembly into place until the injectors are
seated in the ports.
(4) Install the fuel rail mounting bolts. Tighten
bolts to 22 N´m (200 in. lbs.) torque.
(5) Connect the connectors to the fuel injectors.
(6) Install wiring harness to brackets.
(7) Connect the wiring connectors to fuel injectors
harness (Fig. 12).
(8) Connect negative battery cable.
(9) Use the DRBIIItscan tool to pressurize the
fuel system. Check for leaks.
INSTALLATION - 3.3/3.8L
(1) Ensure injector holes are clean. Replace
O-rings if damaged.
(2) Lubricate injector O-rings with a drop of clean
engine oil to ease installation.
(3) Put the tip of each injector into their ports.
Push the assembly into place until the injectors are
seated in the ports.
(4) Install the fuel rail mounting bolts. Tighten
bolts to 22 N´m (200 in. lbs.) torque.
(5) Remove covering on lower intake manifold and
clean surface.
(6) Install the Upper Intake Manifold, refer to
Engine/Manifolds/Upper Intake for more information.
(7) Install fuel hose quick connector fitting to chas-
sis tubes.Refer to Fuel Hoses, Clamps and
Quick Connect Fittings in this Section.Push the
fitting onto the chassis tube until it clicks into place.
Pull on the fitting to ensure complete insertion.
(8) Connect negative cable to battery.
(9) Use the DRBIIItscan tool to pressurize the
fuel system. Check for leaks.
FUEL TANK
DESCRIPTION
The fuel tank is constructed of a plastic material.
Its main functions are for fuel storage and for place-
ment of the fuel pump module. The tank is made
from High density Polyethylene (HDPE) material.If
equipped with ORVR (Onboard Refueling Vapor
Recovery) it has been added to the fuel tank to con-
trol refueling vapor emissions.
Fig. 13 FUEL INJECTORS 3.3/3.8L
14 - 10 FUEL DELIVERYRS
FUEL RAIL (Continued)

OPERATION
All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and
vapor flow controls are required for all fuel tank con-
nections.
All models are equipped with either one or two
check valves mounted into the top of the fuel tank (or
pump module).
An evaporation control system is connected to the
check valve(s)/control valve(Refer to 25 - EMIS-
SIONS CONTROL/EVAPORATIVE EMISSIONS/
ORVR - OPERATION) to reduce emissions of fuel
vapors into the atmosphere, when the tank is vented
due to vapor expansion in the tank. When fuel evap-
orates from the fuel tank, vapors pass through vent
hoses or tubes to a charcoal canister where they are
temporarily held. When the engine is running, the
vapors are drawn into the intake manifold. In addi-
tion, fuel vapors produced during vehicle refueling
are allowed to pass through the vent hoses/tubes to
the charcoal canister(s) for temporary storage (prior
to being drawn into the intake manifold). All models
are equipped with a self-diagnosing system using a
Leak Detection Pump (LDP) or Natural Vacuum
Leak Detection (NVLD). Refer to the Emission Con-
trol System for additional information.
INLET CHECK VALVE
All vehicles have an inlet check valve on the inside
of the fuel tank at the filler inlet
The valve prevents fuel from splashing back on
customer during vehicle refueling. The valve is a
non-serviceable item.
REMOVAL
(1) Remove fuel filler cap and perform Fuel Sys-
tem Pressure Release procedure (Fig. 14).
(2) Disconnect negative cable from battery.
(3) Insert fuel siphon hose into fuel filler neck and
push it into the tank.
(4) Drain fuel tank dry into holding tank or a
properly labeledGASOLINEsafety container.
(5) Raise vehicle on hoist and support.
(6) Use a transmission jack to support fuel tank.
Remove bolts from fuel tank straps.
(7) Lower tank slightly.
(8) Disconnect the fuel filler vent tube. Squeeze
tabs and pull apart (Fig. 15).
(9) Disconnect the fuel fill hose at the fuel tank
filler metal tubeNOT AT THE FUEL TANK(Fig.
15).
(10) Disconnect fuel line and vapor line at the
front of the fuel tank.
The fuel pump module electrical connector
has a retainer that locks it in place.(11) Slide fuel pump module electrical connector
lock to unlock.
(12) Push down on connector retainer (Fig. 16) and
pull connector off module.
(13) Lower tank from vehicle. Remove fuel filler
vent tube from frame (Fig. 17).
Fig. 14 Fuel Tank
1 - ROLLOVER VALVE
2 - FUEL FILLER INLET
3 - ROLLOVER VALVE
4 - FUEL PUMP MODULE
Fig. 15 FUEL FILLER AND VENT TUBE
1 - Filler Tube
2 - Vent Tube
RSFUEL DELIVERY14-11
FUEL TANK (Continued)

INSTALLATION
(1) Position fuel tank on transmission jack. Con-
nect check valve hose. Connect fuel filler tube vent
hose to fuel filler tube.
(2) Feed filler vent line thru frame rail.
(3) Raise tank into position and carefully work fuel
filler metal tube into the rubber hose on fuel tank. A
light coating of clean engine oil on the tube end may
be used to aid assembly.
(4) Tighten strap bolts to 54 N´m (40 ft. lbs.)
torque. Tighten T strap bolt to 28.2 N´m (250 in.
lbs.). Remove transmission jack.
(5) Tighten filler hose clamp to 3.3 N´m (30 in.
lbs.).CAUTION: Ensure straps are not twisted or bent
before or after tightening strap screws.
(6) Connect fuel pump/module electrical connector.
Place retainer in locked position.
(7) Lubricate the fuel supply line with clean 30
weight engine oil, install the quick connect fuel fit-
ting. Refer to Tube/Fitting Assembly in the Fuel
Delivery section of this section.
(8) Connect the control vapor lines at front of
tank.
(9) Pull-pull-push on all connections to make sure
of connection.
(10) Fill fuel tank, replace cap, and connect bat-
tery negative cable.
(11) Use the DRBIIItscan tool to pressurize the
fuel system. Check for leaks.
FUEL TANK FILLER TUBE
REMOVAL
(1) Disconnect the negative battery cable.
(2) Remove the 3 screws at the filler door.
(3) Raise and support vehicle
(4) Remove the left rear tire.
(5) Remove the splash shield (Fig. 19) or (Fig. 18).
(6)For RGRemove the canister from filler tube
(Fig. 20).
(7)For RGDisconnect the vent at the top of the
filler tube.
(8) Remove the ground strap.
(9) Remove filler tube at tank.
Fig. 16 Pump Module Connector Retainer and Lock
1 - PUSH DOWN ON RETAINER
2 - CONNECTOR LOCK
Fig. 17 VENT HOSE
Fig. 18 FUEL FILLER TUBE (RS)
14 - 12 FUEL DELIVERYRS
FUEL TANK (Continued)

INSTALLATION
(1) Install filler tube to tank (Fig. 19).
(2) Install the ground strap.
(3)For RGConnect the vent at the top of the filler
tube.
(4) Install the 3 screws at the filler door.(5)For RGInstall the canister from filler tube
(Fig. 20).
(6) Install the splash shield.
(7) Install the left rear tire.
(8) lower vehicle.
(9) Connect the negative battery cable.
INLET FILTER
REMOVAL
(1) Remove fuel pump module. Refer to Fuel Pump
Module Removal in this section.
(2) Using a thin straight blade screwdriver, pry
back the locking tabs on fuel pump reservoir and
remove the strainer (Fig. 21).
(3) Remove strainer O-ring from the fuel pump
reservoir body.
(4) Remove any contaminants in the fuel tank by
washing the inside of the fuel tank.
INSTALLATION
(1) Lubricate the strainer O-ring with clean engine
oil.
(2) Insert strainer O-ring into outlet of strainer so
that it sits evenly on the step inside the outlet.
(3) Push strainer onto the inlet of the fuel pump
reservoir body. Make sure the locking tabs on the
reservoir body lock over the locking tangs on the
strainer.
(4) Install fuel pump module. Refer to Fuel Pump
Module Installation in this section.
Fig. 19 FUEL FILLER TUBE AND VENT TUBE (RG)
Fig. 20 FUEL TUBE VENT CANISTER (RG)
Fig. 21 Inlet
1 - TABS
2 - INLET STRAINER
RSFUEL DELIVERY14-13
FUEL TANK FILLER TUBE (Continued)

QUICK CONNECT FITTING
STANDARD PROCEDURE - QUICK-CONNECT
FITTINGS
REMOVAL
When disconnecting a quick-connect fitting, the
retainer will remain on the fuel tube nipple.
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE DISCONNECTING A QUICK-CONNECT FIT-
TINGS. REFER TO THE FUEL PRESSURE RELEASE
PROCEDURE. THIS MAY RESULT IN PERSONAL
INJURY OR DEATH.
(1) Perform Fuel Pressure Release Procedure.
Refer to the Fuel Pressure Release Procedure in this
section.
(2) Disconnect negative cable from battery or aux-
iliary jumper terminal.
(3) Squeeze retainer tabs together and pull fuel
tube/quick-connect fitting assembly off of fuel tube
nipple. The retainer will remain on fuel tube.
INSTALLATION
CAUTION: Make sure that the o-ring in installed in
fitting. Never install a quick-connect fitting without
the retainer being either on the fuel tube or already
in the quick-connect fitting. In either case, ensure
the retainer locks securely into the quick-connect
fitting by firmly push-pulling-push on fuel tube and
fitting to ensure it is secured.
(1) Using a clean lint free cloth, clean the fuel tube
nipple and retainer.
(2) Prior to connecting the fitting to the fuel tube,
coat the fuel tube nipple with clean engine oil.
(3) Push the quick-connect fitting over the fuel
tube until theretainer seats and a click is heard.
(4) The plastic quick-connect fitting has windows
in the sides of the casing. When the fitting com-
pletely attaches to the fuel tube, the retainer locking
ears and the fuel tube shoulder are visible in the
windows. If they are not visible, the retainer was not
properly installed (Fig. 22).Do not rely upon the
audible click to confirm a secure connection.
(5) Connect negative cable to battery or auxiliary
jumper terminal.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for several minutes, until the test is stopped, or
until the ignition switch is turned to the Off posi-
tion.(6) Use the DRB IIItscan tool ASD Fuel System
Test to pressurize the fuel system. Check for leaks.
TWO-TAB TYPE FITTING
This type of fitting is equipped with tabs located on
both sides of the fitting (Fig. 23). These tabs are sup-
plied for disconnecting the quick-connect fitting from
component being serviced.
CAUTION: The interior components (O-rings, spac-
ers) of this type of quick-connect fitting are not ser-
viced separately, but new plastic retainers are
available. Do not attempt to repair damaged fittings
or fuel lines/tubes. If repair is necessary, replace
the complete fuel tube assembly.
Fig. 22 Plastic Quick-Connect Fitting/Fuel Tube
Connection
1 - WINDOW
2-TAB(2)
3 - EAR
4 - SHOULDER (ON TUBE)
Fig. 23 Typical Two-Tab Type Quick-Connect Fitting
1 - TAB(S)
2 - QUICK-CONNECT FITTING
14 - 14 FUEL DELIVERYRS

WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
PRESSURE RELEASE PROCEDURE IN THIS
GROUP. THIS MAY RESULT IN PERSONAL INJURY
OR DEATH.
DISCONNECTION/CONNECTION
(1) Perform fuel pressure release procedure. Refer
to Fuel Pressure Release Procedure in this group.
(2) Disconnect negative battery cable from battery
or auxiliary jumper terminal.
(3) Clean fitting of any foreign material before dis-
assembly.
(4) To disconnect quick-connect fitting, squeeze
plastic retainer tabs (Fig. 23) against sides of quick-
connect fitting with your fingers. Tool use is not
required for removal and may damage plastic
retainer. Pull fitting from fuel system component
being serviced. The plastic retainer will remain on
component being serviced after fitting is discon-
nected. The O-rings and spacer will remain in quick-
connect fitting connector body.
(5) Inspect quick-connect fitting body and compo-
nent for damage. Replace as necessary.
CAUTION: When the quick-connect fitting was dis-
connected, the plastic retainer will remain on the
component being serviced. If this retainer must be
removed, very carefully release the retainer from
the component with two small screwdrivers. After
removal, inspect the retainer for cracks or any dam-
age.
(6) Prior to connecting quick-connect fitting to
component being serviced, check condition of fitting
and component. Clean parts with a lint-free cloth.
Lubricate with clean engine oil.
(7) Insert quick-connect fitting to component being
serviced and into plastic retainer. When a connection
is made, a click will be heard.
(8) Verify a locked condition by firmly push-pull-
ing-push on fuel tube and fitting (15-30 lbs.).
(9) Connect negative cable to battery or auxiliary
jumper terminal.
(10) Use the DRB IIItscan tool ASD Fuel System
Test to pressurize the fuel system. Check for leaks.
PLASTIC RETAINER RING TYPE FITTING
This type of fitting can be identified by the use of a
full-round plastic retainer ring (Fig. 24) usually black
in color.CAUTION: The interior components (O-rings, spac-
ers, retainers) of this type of quick-connect fitting
are not serviced separately. Do not attempt to repair
damaged fittings or fuel lines/tubes. If repair is nec-
essary, replace the complete fuel tube assembly.
WARNING: THE FUEL SYSTEM IS UNDER A CON-
STANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRES-
SURE MUST BE RELEASED. REFER TO THE FUEL
SYSTEM PRESSURE RELEASE PROCEDURE IN
THIS GROUP. THIS MAY RESULT IN PERSONAL
INJURY OR DEATH.
DISCONNECTION/CONNECTION
(1) Perform fuel pressure release procedure. Refer
to Fuel Pressure Release Procedure in this section.
(2) Disconnect negative battery cable from battery
or auxiliary jumper terminal.
(3) Clean fitting of any foreign material before dis-
assembly.
(4) To release fuel system component from quick-
connect fitting, firmly push fitting towards compo-
nent being serviced while firmly pushing plastic
Fig. 24 Plastic Retainer Ring Type Fitting
1 - FUEL TUBE
2 - QUICK CONNECT FITTING
3 - PUSH
4 - PLASTIC RETAINER
5 - PUSH
6 - PUSH
7 - PUSH
8 - PUSH
RSFUEL DELIVERY14-15
QUICK CONNECT FITTING (Continued)

retainer ring into fitting (Fig. 24). With plastic ring
depressed, pull fitting from component.The plastic
retainer ring must be pressed squarely into fit-
ting body. If this retainer is cocked during
removal, it may be difficult to disconnect fit-
ting. Use an open-end wrench on shoulder of
plastic retainer ring to aid in disconnection.
(5) After disconnection, plastic retainer ring will
remain with quick-connect fitting connector body.
(6) Inspect fitting connector body, plastic retainer
ring and fuel system component for damage. Replace
as necessary.(7) Prior to connecting quick-connect fitting to
component being serviced, check condition of fitting
and component. Clean parts with a lint-free cloth.
Lubricate with clean engine oil.
(8) Insert quick-connect fitting into component
being serviced until a click is felt.
(9) Verify a locked condition by firmly push-pull-
ing-push on fuel tube and fitting (15-30 lbs.).
(10) Connect negative battery cable to battery or
auxiliary jumper terminal.
(11) Use the DRB IIItscan tool ASD Fuel System
Test to pressurize the fuel system. Check for leaks.
14 - 16 FUEL DELIVERYRS
QUICK CONNECT FITTING (Continued)

FUEL INJECTION
TABLE OF CONTENTS
page page
FUEL INJECTION
OPERATION
OPERATION - INJECTION SYSTEM.......18
OPERATION - MODES OF OPERATION....18
FUEL CORRECTION or ADAPTIVE
MEMORIES..........................20
PROGRAMMABLE COMMUNICATIONS
INTERFACE (PCI) BUS.................21
SYSTEM DIAGNOSIS..................22
SPECIFICATIONS
TORQUE............................22
SPECIAL TOOLS
FUEL...............................23
ACCELERATOR PEDAL
REMOVAL.............................24
INSTALLATION.........................24
CRANKSHAFT POSITION SENSOR
DESCRIPTION.........................25
OPERATION...........................25
REMOVAL.............................25
INSTALLATION - 2.4L....................26
ENGINE SPEED SENSOR
DESCRIPTION.........................26
OPERATION...........................26
FUEL INJECTOR
DESCRIPTION.........................26
OPERATION...........................26
REMOVAL
REMOVAL - 2.4L......................27
REMOVAL - 3.3/3.8L...................27
INSTALLATION
INSTALLATION - 2.4L..................28
INSTALLATION - 3.3/3.8L................28
FUEL PUMP RELAY
DESCRIPTION.........................28
OPERATION...........................28
IDLE AIR CONTROL MOTOR
DESCRIPTION.........................28
OPERATION...........................28REMOVAL.............................29
INSTALLATION.........................29
INLET AIR TEMPERATURE SENSOR
DESCRIPTION.........................30
MAP SENSOR
DESCRIPTION.........................30
OPERATION...........................30
REMOVAL
REMOVAL - 2.4L......................31
REMOVAL - 3.3/3.8L...................31
INSTALLATION
INSTALLATION - 2.4L..................31
INSTALLATION - 3.3/3.8L................31
O2 SENSOR
DESCRIPTION.........................32
OPERATION...........................32
REMOVAL
REMOVAL - UPSTREAM 1/1 - 2.4L........33
REMOVAL - UPSTREAM 1/1 - 3.3/3.8L.....33
REMOVAL - DOWNSTREAM 1/2 - 2.4/3.3/
3.8L................................34
INSTALLATION
INSTALLATION - UPSTREAM 1/1 - 2.4L.....34
INSTALLATION - UPSTREAM 1/1 - 3.3/3.8L . . 34
INSTALLATION DOWNSTREAM 2/1 -
2.4/3.3/3.8L..........................34
THROTTLE BODY
DESCRIPTION.........................35
OPERATION...........................35
REMOVAL.............................35
INSTALLATION.........................35
THROTTLE CONTROL CABLE
REMOVAL.............................35
INSTALLATION.........................36
THROTTLE POSITION SENSOR
DESCRIPTION.........................36
OPERATION...........................36
REMOVAL - 3.3/3.8L.....................36
INSTALLATION - 3.3/3.8L.................37
RSFUEL INJECTION14-17

FUEL INJECTION
OPERATION
OPERATION - INJECTION SYSTEM
All engines used in this section have a sequential
Multi-Port Electronic Fuel Injection system. The MPI
system is computer regulated and provides precise
air/fuel ratios for all driving conditions. The Power-
train Control Module (PCM) operates the fuel injec-
tion system.
The PCM regulates:
²Ignition timing
²Air/fuel ratio
²Emission control devices
²Cooling fan
²Charging system
²Idle speed
²Vehicle speed control
Various sensors provide the inputs necessary for
the PCM to correctly operate these systems. In addi-
tion to the sensors, various switches also provide
inputs to the PCM.
The PCM can adapt its programming to meet
changing operating conditions.
Fuel is injected into the intake port above the
intake valve in precise metered amounts through
electrically operated injectors. The PCM fires the
injectors in a specific sequence. Under most operat-
ing conditions, the PCM maintains an air fuel ratio
of 14.7 parts air to 1 part fuel by constantly adjust-
ing injector pulse width. Injector pulse width is the
length of time the injector is open.
The PCM adjusts injector pulse width by opening
and closing the ground path to the injector. Engine
RPM (speed) and manifold absolute pressure (air
density) are theprimaryinputs that determine
injector pulse width.
OPERATION - MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does for
Wide Open Throttle (WOT). There are several differ-
ent modes of operation that determine how the PCM
responds to the various input signals.
There are two different areas of operation, OPEN
LOOP and CLOSED LOOP.
During OPEN LOOP modes the PCM receives
input signals and responds according to preset PCM
programming. Inputs from the upstream and down-
stream heated oxygen sensors are not monitored dur-
ing OPEN LOOP modes, except for heated oxygensensor diagnostics (they are checked for shorted con-
ditions at all times).
During CLOSED LOOP modes the PCM monitors
the inputs from the upstream and downstream
heated oxygen sensors. The upstream heated oxygen
sensor input tells the PCM if the calculated injector
pulse width resulted in the ideal air-fuel ratio of 14.7
to one. By monitoring the exhaust oxygen content
through the upstream heated oxygen sensor, the
PCM can fine tune injector pulse width. Fine tuning
injector pulse width allows the PCM to achieve opti-
mum fuel economy combined with low emissions.
For the PCM to enter CLOSED LOOP operation,
the following must occur:
(1) Engine coolant temperature must be over 35ÉF.
²If the coolant is over 35ÉF the PCM will wait 38
seconds.
²If the coolant is over 50ÉF the PCM will wait 15
seconds.
²If the coolant is over 167ÉF the PCM will wait 3
seconds.
(2) For other temperatures the PCM will interpo-
late the correct waiting time.
(3) O2 sensor must read either greater than 0.745
volts or less than 0.29 volt.
(4) The multi-port fuel injection systems has the
following modes of operation:
²Ignition switch ON (Zero RPM)
²Engine start-up
²Engine warm-up
²Cruise
²Idle
²Acceleration
²Deceleration
²Wide Open Throttle
²Ignition switch OFF
(5) The engine start-up (crank), engine warm-up,
deceleration with fuel shutoff and wide open throttle
modes are OPEN LOOP modes. Under most operat-
ing conditions, the acceleration, deceleration (with
A/C on), idle and cruise modes,with the engine at
operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the ignition switch activates the fuel injec-
tion system, the following actions occur:
²The PCM monitors the engine coolant tempera-
ture sensor and throttle position sensor input. The
PCM determines basic fuel injector pulse width from
this input.
²The PCM determines atmospheric air pressure
from the MAP sensor input to modify injector pulse
width.
When the key is in the ON position and the engine
is not running (zero rpm), the Auto Shutdown (ASD)
and fuel pump relays de-energize after approximately
14 - 18 FUEL INJECTIONRS