engine mount CHRYSLER CARAVAN 2002 Service Manual

bearing housing, routes the engine oil back to the
crankcase.
The most common turbocharger failure is bearing
failure related to repeated hot shutdowns with inad-
equate ªcool-downº periods. A sudden engine shut
down after prolonged operation will result in the
transfer of heat from the turbine section of the tur-
bocharger to the bearing housing. This causes the oil
to overheat and break down, which causes bearing
and shaft damage the next time the vehicle is
started.Letting the engine idle after extended operation
allows the turbine housing to cool to normal operat-
ing temperature. The following chart should be used
as a guide in determining the amount of engine idle
time required to sufficiently cool down the turbo-
charger before shut down, depending upon the type
of driving and the amount of cargo.
TURBOCHARGER(COOL DOWN(CHART
Driving Load Turbocharger Idle Time
(in
minuetes)
Condition Temperature Before
Shut Down
Stop & Go Empty Cool Less than 1
Stop & Go Medium Warm 1
Highway
SpeedsMedium Warm 2
City Traffic Max.
GCWRWarm 3
Highway
SpeedsMax.
GCWRWarm 4
Uphill
GradeMax.
GCWRHot 5
Fig. 3 Wastegate Operation
1 - SIGNAL LINE
2 - EXHAUST BYPASS VALVE
3 - WASTEGATE
4 - EXHAUST
5 - TURBINE
6 - EXHAUST BYPASS VALVE
7 - WASTEGATE
8 - EXHAUST
9 - TURBINE
10 - SIGNAL LINE
Fig. 4 Turbocharger Oil Supply and Drain
1 - BEARINGS
2 - OIL SUPPLY (FROM ENGINE BLOCK)
3 - OIL RETURN (TO OIL PAN)
RGEXHAUST SYSTEM AND TURBOCHARGER11a-3
TURBOCHARGER SYSTEM (Continued)
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TURBOCHARGER
REMOVAL
The exhaust manifold and turbocharger cannot be
remove with the engine in vehicle.
(1) Remove engine from vehicle and mount on
engine stand (Refer to 9 - ENGINE - REMOVAL).
(2) Remove thermostat to upper radiator hose pipe
(Fig. 5).(3) Remove engine lift hook (Fig. 6).
(4) Remove exhaust manifold heat shield (Fig. 6).
(5) Disconnect turbocharger oil supply and return
lines at turbocharger (Fig. 6).
(6) Remove exhaust manifold retaining nuts (Fig.
6).
(7) Remove exhaust manifold and turbocharger
from engine (Fig. 6).
Fig. 5 TURBOCHARGER AND COOLANT PIPES
1 - TURBOCHARGER OUTLET PIPE RETAINING BOLT
2 - TURBOCHARGER OUTLET PIPE
3 - ADAPTER HOSE
4 - HEAT SHIELD
5 - HOSE CLAMPS
6 - TURBOCHARGER INLET PIPE RETAINING BOLT
7 - TURBOCHARGER INLET PIPE
8 - ADAPTER HOSE
9 - HOSE CLAMPS
10 - CLAMP
11 - EGR VALVE TO INTAKE AIR INLET PIPE
12 - CLAMP
13 - THERMOSTAT HOUSING TO UPPER RADIATOR HOSE
PIPE
Fig. 6 EXHAUST MANIFOLD AND TURBOCHARGER
1 - TURBOCHARGER OIL SUPPLY BANJO BOLT
2 - COPPER WASHER
3 - EXHAUST MANIFOLD GASKET
4 - COPPER WASHER
5 - EXHAUST MANIFOL HEAT SHIEL RETAINING BOLT
6 - TURBOCHARGER
7 - ENGINE LIFT HOOK
8 - ENGINE LIFT HOOK RETAINING BOLT
9 - SPACER
10 - EXHAUST MANIFOLD RETAINING NUT
11 - TURBOCHARGER OIL RETURN HOSE
12 - HOSE CLAMPS
13 - EXHAUST MANIFOLD STUDS
11a - 4 EXHAUST SYSTEM AND TURBOCHARGERRG
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SPECIFICATIONS - TORQUE
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Front Cradle Crossmember to Fram Rail Attaching Bolts (4) 163 120 Ð
Reinforcement Plate to Crossmember Attaching Bolt Size M14 (9) 153 113 Ð
Reinforcement Plate to Crossmember Attaching Bolt Size M12 (1) 106 78 Ð
Reinforcement Plate to Crossmember Attaching Bolt Size M10 (4) 61 45 Ð
Rear Engine Mount to Crossmember Attaching Through Bolt 68 50 Ð
Radiator Support Crossmember Attaching Bolts 51 38 Ð
FRONT CRADLE
CROSSMEMBER
DESCRIPTION
DESCRIPTION - FRONT CRADLE
CROSSMEMBER
This vehicle uses a one piece cast aluminum cradle
for the front cradle crossmember. The cradle cross-
member is used as the attaching points for the lower
control arms, stabilizer bar and steering gear. The
cradle also has the power steering hoses and the
chassis brake tubes attached to it.
WARNING: If a threaded hole in the suspension cra-
dle needs to be repaired, only use the type of
thread insert and installation procedure specified
for this application.
The threaded holes in the front cradle crossmem-
ber that are used for attachment of the lower control
arm rear bushing retainer, power steering hose and
chassis brake tubes can be repaired. The repair is
done by the installation of a Heli-Coiltthread insert
which has been specifically developed for this appli-
cation. Refer to the Mopar Parts Catalog for the spec-
ified Heli-Coiltthread insert to be used for this
application. The procedure for installing the Heli-
Coiltthread insert is detailed in the Service Proce-
dures section in this group of the service manual.
DESCRIPTION - FRONT CRADLE
CROSSMEMBER THREAD REPAIR
WARNING: When performing this procedure use
only the thread inserts which are specified in the
Mopar Parts Catalog for this repair procedure.
These thread inserts have been specifically devel-
oped for this application and use of other types of
thread inserts can result in an inferior long term
repair.The threaded holes in the front cradle crossmem-
ber, if damaged, can repaired by installing a Heli-
Coiltthread insert.
The threaded holes that are repairable using the
thread insert, are the lower control arm rear bushing
retainer mounting bolt holes, routing bracket attach-
ing locations for the power steering hoses, and brake
hose attachment holes.
This repair procedure now allows the threaded
holes in the cradle crossmember to be repaired, elim-
inating the need to replace the cradle crossmember if
damage occurs to one of the threaded holes.
The thread inserts for this application are specified
by part number in the Mopar Parts Catalog.Do not
use a substitute thread insert.
The specific tools and equipment required to install
the thread insert are listed below. Refer to the
instructions included with the thread insert for the
detailed procedure used for the installation of the
thread insert.
NOTE: The thread inserts for this application are for
the repair of M8x1.25 and M10x1.5 threads. Be sure
the correct tools are used for the required thread
insert size.
TOOL REQUIREMENT FOR M8x1.25 Thread
²8.3mm (5/16 in.) Drill Bit
²120É Countersink
²Heli-CoiltTap #4863-8
²Heli-CoiltGage #4624-8
²Heli-CoiltHand Inserting Tool 7751-8
²Needle Nose Pliers ± For Removal Of Thread
Insert Driving Tang
TOOL REQUIREMENT FOR M10x1.5 Thread
²10.5mm (25/64 in.) Drill Bit
²120É Countersink
²Heli-CoiltTap #4863-10
²Heli-CoiltGage #4624-10
²Heli-CoiltHand Inserting Tool 7751-10
²Needle Nose Pliers ± For Removal Of Thread
Insert Driving Tang
RSFRAME & BUMPERS13-9
FRAME (Continued)
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REMOVAL
The front cradle crossmember must be installed in
the design location to achieve proper front end sus-
pension alignment. If the cradle crossmember is
removed without applying reference marks on the
frame rails, align the cradle crossmember according
to the dimensions provided in this group.
NOTE: If the caged nuts in the frame rails become
damaged and cannot be reused, a replacement nut
can be obtained through MoparT.
REMOVAL
(1) Disconnect battery negative cable.
(2) Remove steering column lower cover from
instrument panel (Refer to 23 - BODY/INSTRU-
MENT PANEL/STEERING COLUMN OPENING
COVER - REMOVAL).
(3) Remove steering column cover backing plate
(Refer to 23 - BODY/INSTRUMENT PANEL/STEER-
ING COLUMN COVER BACKING PLATE - REMOV-
AL).
(4) Position steering so front wheels are straight
ahead.
CAUTION: Do not rotate steering wheel after disen-
gaging lower coupling from steering gear, damage
to air bag clock spring can result.
(5) Remove clinch bolt attaching steering column
coupling to steering gear shaft (Fig. 10).(6) Remove steering column coupling from tele-
scoping steering gear shaft.
(7) Hoist vehicle and support on safety stands.
(8) Position a drain pan under power steering
pump and oil return hose coupling.
(9) Using a hose pinch-off pliers (C-4390), pinch
power steering oil return hose off between the cross-
member coupling and the pump.
(10) Loosen hose clamp at the cradle crossmember
coupling.
(11) Disconnect return hose from metal tube.
(12) While holding pressure relief valve nut on
back of power steering pump, Remove flare nut
attaching high pressure hose to back of pump.
(13) Remove high pressure hose from pump.
(14) Allow power steering fluid to drain into pan.
(15) Remove bolts attaching anti-lock brake sensor
leads to cradle crossmember.
(16) Position anti-lock brake leads out of the way.
(17) Disconnect stabilizer bar links from ends of
stabilizer bar.
(18) Disconnect lower ball joints from lower steer-
ing knuckles (Refer to 2 - SUSPENSION/FRONT/
LOWER BALL JOINT - REMOVAL).
(19) Remove the rear engine mount heat shield
(Fig. 11).
(20) Remove through bolt attaching rear engine
mount to cradle crossmember (Fig. 12).
(21) Using paint or grease pencil, mark outline of
cradle crossmember on frame rails to aid installation.
(22) Support cradle crossmember on suitable lift-
ing device (Fig. 14).
(23) Remove bolts attaching crossmember to front
frame rails (Fig. 13).
Fig. 10 STEERING COUPLING
1 - STEERING SHAFT BOOT
2 - STEERING SHAFT
3 - CROSSMEMBER
4 - STEERING GEAR
5 - MOUNT
6 - TRANSAXLE
Fig. 11 REAR MOUNT HEAT SHIELD
1 - BOLT
2 - HEAT SHIELD
3 - CLIP
4 - REAR ENGINE MOUNT
13 - 10 FRAME & BUMPERSRS
FRONT CRADLE CROSSMEMBER (Continued)
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(24)Remove cradle crossmember from vehicle (Fig. 14).
Fig. 12 REAR MOUNT
1 - BOLT
2 - REAR MOUNT BRACKET
3 - THROUGH BOLT
4 - REAR MOUNT
Fig. 13 CRADLE CROSSMEMBER MOUNT
1 - CROSSMEMBER MOUNT
2 - BRAKE HOSE MOUNT
3 - STEERING TIE ROD
4 - FRONT CROSSMEMBER
5 - FRAME RAIL
Fig. 14 CRADLE CROSSMEMBER
1 - ENGINE OIL PAN
2 - TRANSAXLE
3 - LOWER CONTROL ARM4 - FRONT CROSSMEMBER
5 - LIFT DEVICE
6 - SPINDLE
RSFRAME & BUMPERS13-11
FRONT CRADLE CROSSMEMBER (Continued)
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INSTALLATION
NOTE: If cradle crossmember requires replacement.
Refer to Group 2, Suspension, to transfer suspen-
sion components and Group 19, Steering, to trans-
fer steering components.
(1) Support crossmember on suitable lifting device
(Fig. 14).
(2) Position crossmember to vehicle.
(3) Loosely install bolts attaching cradle cross-
member to front frame rails.
(4) Align crossmember to previously made marks
on frame rails.
(5) Tighten bolts attaching cradle crossmember to
frame rails.
(6) Install through bolt attaching rear engine
mount to cradle crossmember (Fig. 12) and tighten to
68 N´m (50 ft. lbs.) torque.
(7) Install the rear mount heat shield (Fig. 11).
(8) Connect lower ball joints to steering knuckles
(Refer to 2 - SUSPENSION/FRONT/LOWER BALL
JOINT - INSTALLATION)
(9) Connect stabilizer bar links to ends of stabi-
lizer bar.
(10) Install bolts attaching anti-lock brake sensor
leads to cradle crossmember.
(11) Install high pressure hose to pump.
(12) Connect return hose to metal tube.
(13) Tighten hose clamp at the cradle crossmember
coupling.
(14) Remove pinch-off pliers.
(15) Position steering so front wheels are straight
ahead.
(16) Install steering column coupling to telescoping
steering gear shaft.
(17) Install clinch bolt attaching steering column
coupling to steering gear shaft.
(18) Install steering column cover backing plate
(Refer to 23 - BODY/INSTRUMENT PANEL/STEER-
ING COLUMN COVER BACKING PLATE -
INSTALLATION)
(19) Install steering column lower cover from
instrument panel (Refer to 23 - BODY/INSTRU-MENT PANEL/STEERING COLUMN OPENING
COVER - INSTALLATION).
(20) Connect battery negative cable.
FRONT CROSSMEMBER
MOUNT BUSHINGS
REMOVAL
(1) Using paint or grease pencil, mark outline of
cradle crossmember on frame rails.
(2) Loosen bolts attaching crossmember to frame
rails.
(3) Remove bolt on bushing that requires replace-
ment.
(4) Allow cradle crossmember to drop down enough
to gain clearance for bushing removal.
(5) Remove bushing from vehicle.
INSTALLATION
(1) Apply rubber lubrication or soap to replace-
ment bushing.
(2) Insert lower half of bushing into square hole in
cradle crossmember.
(3) Place upper half of bushing on top of cross-
member aligned to receive square tube protruding
upward from lower bushing half.
(4) Squeeze bushing halves together to ensure they
are properly mated.
(5) Lift cradle crossmember upward to close gap
between the bushing and frame.
(6) Verify that lower bushing is fully seated into
cradle crossmember and upper bushing.
(7) Install bolt attaching bushing and crossmember
to frame rail hand tight.
(8) Align cradle crossmember to reference marks
on frame rails.
(9) Tighten cradle crossmember to frame rails
attaching bolts to 163 N´m (120 ft. lbs.) torque.
13 - 12 FRAME & BUMPERSRS
FRONT CRADLE CROSSMEMBER (Continued)
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FUEL DELIVERY
DESCRIPTION
DESCRIPTION
The front wheel drive car uses a plastic fuel tank
located rear center of the vehicle.
The Fuel Delivery System consists of: the following
items:
²Electric fuel pump module
²Fuel filter
²Tubes/lines/hoses
²Fuel injectors
The in-tank fuel pump module contains the fuel
pump. The pump is serviced as part of the fuel pump
module. Refer to Fuel Pump Module.
The fuel filter is replaceable, it is mounted on the
outside, on top of, the fuel tank. Refer to the Main-
tenance Schedules in the Introduction section of this
manual for recommended fuel filter replacement
intervals.
DESCRIPTION - FFV REPLACEMENT PARTS
Many components in a Flexible Fuel Vehicle (FFV)
are designed to be compatible with ethanol. Always
be sure that the vehicle is serviced with correct etha-
nol compatible parts.
CAUTION: Replacing fuel system components with
non-ethanol compatible components can damage
your vehicle and may void the warranty.
OPERATION
The fuel system provides fuel pressure by an
in-tank pump module. The PCM controls the opera-
tion of the fuel system by providing battery voltage
to the fuel pump through the fuel pump relay. The
PCM requires only three inputs and a good ground to
operate the fuel pump relay. The three inputs are:²Ignition voltage
²Crankshaft Position (CKP) sensor
²Camshaft Position (CMP) sensor
DIAGNOSIS AND TESTING - FUEL DELIVERY
SYSTEM
(Refer to Appropriate Diagnostic Information)
STANDARD PROCEDURE
STANDARD PROCEDURE - FUEL SYSTEM
PRESSURE RELEASE PROCEDURE
(1) Remove Fuel Pump relay from Power Distribu-
tion Center (PDC). For location of relay, refer to label
on underside of PDC cover.
(2) Start and run engine until it stalls.
(3) Attempt restarting engine until it will no
longer run.
(4) Turn ignition key to OFF position.
(5) Return fuel pump relay to PDC.
(6) One or more Diagnostic Trouble Codes (DTC's)
may have been stored in PCM memory due to fuel
pump relay removal. The DRB IIItscan tool must be
used to erase a DTC.
STANDARD PROCEDURE - DRAINING FUEL
TANK
(1) Release fuel system pressure, refer to the Fuel
System Release Procedure in this section.
(2) Insert a 1/4 inch siphon (max. O. D. 5/16) hose
from a portable fuel siphoning tank through the fuel
filler neck opening into the fuel tank. Hose most
have a 30 degree angle cut on the end to bypass the
check valve in the end of the filler neck. Refer to the
siphoning tank's Manufacturing Instructions.
(3) Drain fuel from fuel tank into siphoning tank.
14 - 2 FUEL DELIVERYRS
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leaks are not present. The component should be
replaced immediately if there is any evidence of deg-
radation that could result in failure.
Never attempt to repair a plastic fuel line/tube.
Replace as necessary.
Avoid contact of any fuel tubes/hoses with other
vehicle components that could cause abrasions or
scuffing. Be sure that the plastic fuel lines/tubes are
properly routed to prevent pinching and to avoid heat
sources.
FUEL PRESSURE REGULATOR
OPERATION
The fuel system uses a nonadjustable pressure reg-
ulator that maintains fuel system pressure at
approximately 400  34 kPa (58  5 psi). The fuel
pressure regulator contains a diaphragm, calibrated
spring and a fuel return valve. The spring pushes
down on the diaphragm and closes off the fuel return
port. System fuel pressure reflects the amount of fuel
pressure required to open the return port.
The pressure regulator is a mechanical device that
is NOT controlled by the PCM or engine vacuum.
REMOVAL
The fuel pressure regulator is part of the fuel
pump module (Fig. 9). Remove the fuel pump module
from the fuel tank to access the fuel pressure regula-
tor. Refer to the Fuel Pump Module removal in this
section.
(1) Spread tangs on pressure regulator retainer.
(2) Pry fuel pressure regulator out of housing.
(3) Ensure both upper and lower O-rings were
removed with regulator.
INSTALLATION
The fuel pressure regulator is part of the fuel
pump module. Remove the fuel pump module from
the fuel tank to access the fuel pressure regulator.
Refer to the Fuel Pump Module removal in this sec-
tion.
(1) Lightly lubricate the O-rings with clean engine
oil and place them into opening in pump module (Fig.
9).
(2) Push regulator into opening in pump module.
(3) Fold tangs on regulator retainer over tabs on
housing.
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).
NOTE: Checkvalve maintains volume of fuel in the
rail and lines, not pressure.
Fig. 9 Fuel Pressure Regulator O-rings
1 - UPPER O-RING
2 - LOWER 0-RING
RSFUEL DELIVERY14-7
FUEL LINES (Continued)
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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. 13).
(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.
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
rollover valves mounted into the top of the fuel tank
(or pump module).
An evaporation control system is connected to the
rollover 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). Refer to the Emission
Control 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.
Fig. 14 FUEL INJECTORS 3.3/3.8L
14 - 10 FUEL DELIVERYRS
FUEL RAIL (Continued)
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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
RSFUEL INJECTION14-17
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