14-1 CHRYSLER TOWN AND COUNTRY 2002 Service Manual
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Page 56 of 2399
the outer joint of the driveshaft out of the hub/bear-
ing.
(15) Remove the hub/bearing to axle mounting
bolts (Fig. 13).
CAUTION: Corrosion may occur between the hub/
bearing and the axle. If this occurs the hub/bearing
will be difficult to remove from the axle. If the hub/
bearing will not come out of the axle by pulling on
it by hand, do not pound on the hub/bearing to
remove it from the axle. Pounding on the hub/bear-
ing to remove it from the axle will damage the hub/
bearing. This damage will result in noise or failure
of the hub/bearing. To remove a hub/bearing which
is corroded to the axle, lightly tap the disc brake
caliper adapter using a soft faced hammer. This will
remove both the disc brake caliper adapter and
hub/bearing from the axle. The hub/bearing will
then need to be removed from the caliper adapter.
(16) Remove the hub/bearing from the axle. (Fig.
12).
(17) If the disc brake caliper adapter and hub/
bearing were removed as an assembly from the axle
and the hub/bearing cannot be removed from the
adapter by hand, use the following procedure to
remove it from the adapter. With a helper supporting
the caliper adapter in his hands, position Remover,
Special Tool 8214-1 on the cast housing of hub/bear-
ing (Fig. 11).Do not position special tool on
inner race of hub/bearing.Lightly strike Remover,
Special Tool 8214-1 with a hammer to remove the
hub/bearing from the caliper adapter.INSTALLATION
FRONT-WHEEL-DRIVE VEHICLES
(1) Install the 4 hub and bearing to axle mounting
bolts into the holes in the flange of the rear axle.
(2)
Install the rear brake support plate on the 4
mounting bolts installed in the flange of the rear axle.
(3) Align the rear hub and bearing with the 4
mounting bolts and start mounting bolts into hub
and bearing. Tighten the 4 bolts in a crisscross pat-
tern until the hub and bearing and brake support
plate is fully and squarely seated onto flange of rear
axle. Tighten the 4 mounting bolts to a torque of 129
N´m (95 ft. lbs.)
NOTE: If equipped with antilock brakes, make sure
wheel speed sensor stays clean and dry as it is
installed into the hub and bearing cap.
(4) If the vehicle is equipped with antilock brakes,
perform the following:
(a) If metal sensor retaining clip is not in the
neutral installed position on hub and bearing cap,
install from the bottom, if necessary, and push clip
upward until it snaps into position.
(b)
Install wheel speed sensor head into rear of
hub and bearing aligning index tab with the notch in
the top of the mounting hole. Push the sensor in until
it snaps into place on the metal retaining clip.
(c) Install secondary (yellow) retaining clip over
wheel speed sensor head and engage the tabs on
each side (Fig. 8).
(5) Install brake drum or disc brake rotor and
brake caliper. (Refer to 5 - BRAKES/HYDRAULIC/
MECHANICAL/DRUM - INSTALLATION)(Refer to 5
- BRAKES/HYDRAULIC/MECHANICAL/ROTOR -
INSTALLATION)
(6) Install wheel and tire (Refer to 22 - TIRES/
WHEELS - INSTALLATION). Tighten the wheel
nuts in the proper sequence to a torque of 135 N´m
(100 ft. lbs.).
(7) Adjust the rear brakes as necessary. (Refer to 5
- BRAKES/HYDRAULIC/MECHANICAL/BRAKE
PADS/SHOES - ADJUSTMENTS)
(8) Lower vehicle.
(9) Road test vehicle to ensure proper operation of
brakes.
ALL-WHEEL-DRIVE VEHICLES
(1) Install hub/bearing on end of axle. (Fig. 12).
(2) Install the hub/bearing mounting bolts. In a
progressive crisscross pattern, tighten the 4 hub/
bearing mounting bolts (Fig. 13) until the disc brake
caliper adapter and hub/bearing are squarely seated
against the axle. Then tighten the hub/bearing
mounting bolts to a torque of 129 N´m (95 ft. lbs.).Fig. 11 Hub/Bearing Removal From Caliper Adapter
1 - SPECIAL TOOL 8214-1
2 - PARK BRAKE CABLE
3 - DISC BRAKE CALIPER ADAPTER
4 - HUB/BEARING
RSREAR SUSPENSION2-33
HUB / BEARING (Continued)
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Page 208 of 2399
CAUTION: Corrosion may occur between the hub/
bearing and the axle flange. If this occurs, the hub/
bearing will be difficult to remove from the axle and
disc brake caliper adapter. If the hub/bearing will
not come out by pulling on it by hand, don't not
pound on it with a hammer. Pounding on the hub/
bearing will damage it. To remove a hub/bearing
that is corroded in place, lightly tap the disc brake
caliper adapter using a soft-face hammer. This will
remove both the caliper adapter and hub/bearing
together from the axle. With a helper supporting the
caliper adapter in his hands, position Remover,
Special Tool 8214-1, on the cast housing of hub/
bearing (Fig. 138). Do not position the special tool
on the inner race of hub/bearing. Lightly strike the
Remover with a hammer to remove the hub/bearing
from the caliper adapter.
(20) Remove the adapter from the rear axle.
(21) Mount the adapter in a vise using the anchor
boss for the park brake cable (Fig. 139).
Fig. 137 Hub/Bearing Removal/Installation (AWD
Shown)
1 - PARK BRAKE BRAKE SHOE
2 - OUTER C/V JOINT
3 - HUB/BEARING
4 - PARK BRAKE BRAKE SHOE
5 - STUB SHAFT
Fig. 138 Hub/Bearing Removal From Caliper Adapter
1 - SPECIAL TOOL 8214-1
2 - PARK BRAKE CABLE
3 - DISC BRAKE CALIPER ADAPTER
4 - HUB/BEARING
Fig. 139 Adapter Mounted In Vise
1 - ADAPTER
2 - PARK BRAKE CABLE BOSS
3 - VISE
4 - PARK BRAKE BRAKE SHOES
RSBRAKES - BASE5-79
SHOES - PARKING BRAKE (Continued)
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RADIATOR DRAINCOCK
REMOVAL
CAUTION: Use of pliers on draincock is not recom-
mended. Damage may occur to radiator or drain-
cock.
NOTE: It is not necessary to remove draincock dur-
ing a routine coolant drain.
(1) Drain the cooling system. (Refer to 7 - COOL-
ING - STANDARD PROCEDURE)
(2) Open the draincock by turning it counterclock-
wise until it stops.
(3) Turn the draincock back (clockwise) 1/8 turn.
(4) Pull the draincock (Fig. 16) from the radiator
tank.
INSTALLATION
(1) Align draincock stem to radiator tank opening.
(2) Push draincock into the radiator tank opening.
(3) Tighten the draincock by turning clockwise
until it stops.
(4) Fill the cooling system. (Refer to 7 - COOLING
- STANDARD PROCEDURE)
RADIATOR PRESSURE CAP
DESCRIPTION
The cooling system pressure cap is located on the
radiator. The cap construction includes; stainless
steel swivel top, rubber seals, and retainer, main
spring, and a spring loaded valve (Fig. 17).
OPERATION
The cooling system is equipped with a pressure cap
that releases excessive pressure; maintaining a range
of 97-124 kPa (14-18 psi).
The cooling system will operate at higher than
atmospheric pressure. The higher pressure raises the
coolant boiling point thus, allowing increased radia-
tor cooling capacity.
There is also a vent valve in the center of the cap.
This valve also opens when coolant is cooling and
contracting, allowing the coolant to return to cooling
system from coolant reserve system tank by vacuum
through a connecting hose.If valve is stuck shut,
or the coolant recovery hose is pinched, the
radiator hoses will be collapsed on cool down.
Clean the vent valve (Fig. 17) and inspect cool-
ant recovery hose routing, to ensure proper
sealing when boiling point is reached.
The gasket in the cap seals the filler neck, so that
vacuum can be maintained, allowing coolant to be
drawn back into the radiator from the reserve tank.
If the gasket is dirty or damaged, a vacuum
may not be achieved, resulting is loss of coolant
and eventual overheating due to low coolant
level in radiator and engine.
Fig. 16 Draincock
1 - RADIATOR TANK
2 - DRAINCOCK
Fig. 17 Cooling System Pressure Cap Filler Neck
1 - OVERFLOW NIPPLE
2 - MAIN SPRING
3 - GASKET RETAINER
4 - STAINLESS-STEEL SWIVEL TOP
5 - RUBBER SEALS
6 - VENT VALVE
7 - RADIATOR
8 - FILLER NECK
RSENGINE7-27
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RADIATOR PRESSURE CAP
DESCRIPTION
The cooling system pressure cap is located on the
radiator. The cap construction includes; stainless
steel swivel top, rubber seals, and retainer, main
spring, and a spring loaded valve (Fig. 19).
OPERATION
The cooling system is equipped with a pressure cap
that releases excessive pressure; maintaining a range
of 97-124 kPa (14-18 psi).
The cooling system will operate at higher than
atmospheric pressure. The higher pressure raises the
coolant boiling point thus, allowing increased radia-
tor cooling capacity.
There is also a vent valve in the center of the cap.
This valve also opens when coolant is cooling and
contracting, allowing the coolant to return to cooling
system from coolant reserve system tank by vacuum
through a connecting hose.If valve is stuck shut,
or the coolant recovery hose is pinched, the
radiator hoses will be collapsed on cool down.
Clean the vent valve (Fig. 19) and inspect cool-
ant recovery hose routing, to ensure proper
sealing when boiling point is reached.
The gasket in the cap seals the filler neck, so that
vacuum can be maintained, allowing coolant to be
drawn back into the radiator from the reserve tank.
If the gasket is dirty or damaged, a vacuum
may not be achieved, resulting is loss of coolant
and eventual overheating due to low coolant
level in radiator and engine.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - COOLING SYSTEM
PRESSURE CAP
Dip the pressure cap in water. Clean any deposits
off the vent valve or its seat and apply cap to end of
the Pressure Cap Test Adaptor that is included with
the Cooling System Tester 7700. Working the
plunger, bring the pressure to 104 kPa (15 psi) on the
gauge. If the pressure cap fails to hold pressure of at
least 97 kPa (14 psi), replace the pressure cap.
CAUTION: The Cooling System Tester Tool is very
sensitive to small air leaks that will not cause cool-
ing system problems. A pressure cap that does not
have a history of coolant loss should not be
replaced just because it leaks slowly when tested
with this tool. Add water to the tool. Turn tool
upside down and recheck pressure cap to confirm
that cap is bad.
If the pressure cap tests properly while positioned
on Cooling System Tester (Fig. 20), but will not hold
pressure or vacuum when positioned on the filler
neck. Inspect the filler neck and cap top gasket for
irregularities that may prevent the cap from sealing
properly.
Fig. 19 Cooling System Pressure Cap Filler Neck
1 - OVERFLOW NIPPLE
2 - MAIN SPRING
3 - GASKET RETAINER
4 - STAINLESS-STEEL SWIVEL TOP
5 - RUBBER SEALS
6 - VENT VALVE
7 - PRESSURE BOTTLE
8 - FILLER NECK
Fig. 20 Testing Cooling System Pressure Cap
1 - PRESSURE CAP
2 - PRESSURE TESTER
RGENGINE7a-25
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(23) Remove cylinder head assembly from engine
block (Fig. 18).
CLEANING
Thoroughly clean the engine cylinder head and cyl-
inder block mating surfaces. Clean the intake and
exhaust manifold and engine cylinder head mating
surfaces. Remove all gasket material and carbon.
Check to ensure that no coolant or foreign material
has fallen into the tappet bore area.
Remove the carbon deposits from the combustion
chambers and top of the pistons.
INSPECTION
Use a straightedge and feeler gauge to check the
flatness of the engine cylinder head and block mating
surfaces.
The minimum cylinder head thickness is 89.95mm
(3.541 in.).
INSTALLATION
CAUTION: Piston protrusion must be measured to
determine cylinder head gasket thickness if one or
more cylinder liners have been replaced (Refer to 9
- ENGINE/CYLINDER HEAD - STANDARD PROCE-
DURE).
NOTE: If cylinder liner(s) have not been removed,
the same thickness head gasket that was removed
can be used.
(1) Clean and inspect gasket mating surfaces.
(2) Position correct head gasket on engine block.
(3) Place cylinder head on engine block (Fig. 18).
CAUTION: New cylinder head bolts must be used.
(4) Tighten cylinder head bolts following procedure
below.
Cylinder Head Bolt Torquing Procedure
(1) Lubricate cylinder head bolts with engine oil.
(2) Torque bolts to 30N´m in numerical starting
with bolt #1 (Fig. 19).
(3) Tighten all bolts an additional 75É, starting
with bolt #4 then 5-6-7-8-9-10-1-2-3 (Fig. 19).
(4) Tighten all bolts an additional 50É in numerical
order starting with bolt #11 then 12-13-14-15-16-
17-18 (Fig. 19).
(5) Without loosening any bolts tighten all bolts an
additional 75É in the following seguence: 4-5-6-7-8-9-
10-1-2-3-11-12-13-14-15-16-17-18.
Fig. 18 CYLINDER HEAD ASSEMBLY
1 - VALVE SPRING
2 - CYLINDER HEAD BOLT
3 - GLOW PLUG
4 - COOLANT TEMPERATURE SENSOR
5 - CYLINDER HEAD ALIGNMENT DOWEL
6 - CYLINDER BLOCK
7 - CYLINDER LINER
8 - ENGINE BLOCK DECK
9 - CYLINDER HEAD GASKET
10 - CYLINDER HEAD
11 - ROCKER ARM AND LIFTER ASSEMBLY
Fig. 19 CYLINDER HEAD TORQUE SEQUENCE
RGENGINE9a-21
CYLINDER HEAD (Continued)
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FUEL SYSTEM
TABLE OF CONTENTS
page page
FUEL DELIVERY..........................1FUEL INJECTION........................16
FUEL DELIVERY
TABLE OF CONTENTS
page page
FUEL DELIVERY
DESCRIPTION
DESCRIPTION........................2
DESCRIPTION - FFV REPLACEMENT
PARTS...............................2
OPERATION............................2
DIAGNOSIS AND TESTING - FUEL DELIVERY
SYSTEM.............................2
STANDARD PROCEDURE
STANDARD PROCEDURE - FUEL SYSTEM
PRESSURE RELEASE PROCEDURE.......2
STANDARD PROCEDURE - DRAINING
FUEL TANK...........................2
SPECIFICATIONS
FUEL SYSTEM PRESSURE..............3
TORQUE.............................3
SPECIAL TOOLS
FUEL................................3
FUEL FILTER
REMOVAL.............................4
INSTALLATION..........................4
FUEL LEVEL SENDING UNIT / SENSOR
DESCRIPTION..........................4
OPERATION............................4
REMOVAL.............................4
INSTALLATION..........................6
FUEL LINES
DESCRIPTION - FUEL LINES/HOSES AND
CLAMPS.............................6
STANDARD PROCEDURE - HOSES AND
CLAMP..............................6
FUEL PRESSURE REGULATOR
OPERATION............................7REMOVAL.............................7
INSTALLATION..........................7
FUEL PUMP
DESCRIPTION..........................7
OPERATION............................7
FUEL PUMP MODULE
DESCRIPTION..........................8
OPERATION............................8
REMOVAL.............................8
INSTALLATION..........................9
FUEL RAIL
REMOVAL
REMOVAL - 2.4L.......................9
REMOVAL - 3.3/3.8L....................9
INSTALLATION
INSTALLATION - 2.4L..................10
INSTALLATION - 3.3/3.8L................10
FUEL TANK
DESCRIPTION.........................10
OPERATION...........................10
REMOVAL.............................11
INSTALLATION.........................11
FUEL TANK FILLER TUBE
REMOVAL.............................12
INSTALLATION.........................12
INLET FILTER
REMOVAL.............................13
INSTALLATION.........................13
QUICK CONNECT FITTING
STANDARD PROCEDURE - QUICK-CONNECT
FITTINGS...........................13
RSFUEL SYSTEM14-1
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REMOVAL
(1) Remove fuel filler cap and perform Fuel Sys-
tem Pressure Release procedure (Fig. 15).
(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. 16).
(9) Disconnect the fuel fill hose at the fuel tank
filler metal tubeNOT AT THE FUEL TANK(Fig.
16).
(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 (Fig. 17).
(12) Push down on connector retainer (Fig. 18) and
pull connector off module.
(13) Lower tank from vehicle. Remove fuel filler
vent tube from frame (Fig. 19).
INSTALLATION
(1) Position fuel tank on transmission jack. Con-
nect rollover valve hose. Connect fuel filler tube vent
hose and tighten clamp.
(2) Raise tank into position and carefully work
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.
Fig. 15 Fuel Tank
1 - ROLLOVER VALVE
2 - FUEL FILLER INLET
3 - ROLLOVER VALVE
4 - GROUND STRAP
5 - FUEL FILTER
6 - FUEL PUMP MODULEFig. 16 FUEL FILLER AND VENT TUBE
1 - Filler Tube
2 - Vent Tube
Fig. 17 Fuel Line Retainers and Pump Connector
Lock
1 - PUSH
2 - CONNECTOR LOCK
3 - QUICK CONNECT RETAINERS
RSFUEL DELIVERY14-11
FUEL TANK (Continued)
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Page 1464 of 2399
(4) Install the 3 screws at the filler door.
(5) Install the canister from filler tube (Fig. 21).
(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. 22).
(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.
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.
(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: Never install a quick-connect fitting with-
out 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 pulling on fuel tube and fit-
ting 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.
Fig. 21 FUEL TUBE VENT CANISTER
Fig. 22 Inlet
1 - TABS
2 - INLET STRAINER
RSFUEL DELIVERY14-13
FUEL TANK FILLER TUBE (Continued)
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Page 1466 of 2399
(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 pulling 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. 25) 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.
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
retainer ring into fitting (Fig. 25). 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 pulling 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.
Fig. 25 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)
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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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