Acceleration CHRYSLER VOYAGER 2004 Service Manual

SHOCK ABSORBER
DESCRIPTION
There is one shock absorber on each side of the
rear suspension. The top of each shock absorber is
bolted to the frame rail. The bottom of each shock
absorber is bolted to the rear axle.
This vehicle is available with either standard type
or load-leveling shock absorbers. On the exterior,
load-leveling shock absorbers are larger in diameter
than standard shock absorbers. The load-leveling
shock absorbers mount the same as the standard
shock absorbers.
OPERATION
The shock absorber dampens jounce and rebound
motions of the spring and suspension.
Each load-leveling shock absorber is a self-leveling,
self-contained vehicle leveling system and shock
absorber combined. It does not require an external
compressor, hoses, or height leveling sensors. All the
height leveling sensors, hydraulic pump, etc., are
contained inside the shock absorber. It uses road
inputs (bumps, stops, starts, turns, acceleration,
deceleration, etc.) to activate pumping, which results
in the extension and compression of the shock
absorber.
REMOVAL - SHOCK ABSORBER
(1) Raise vehicle. (Refer to LUBRICATION &
MAINTENANCE/HOISTING - STANDARD PROCE-
DURE)
(2) Support the rear axle of the vehicle using 2
jackstands positioned at the outer ends of the axle.
NOTE: If the shock absorber lower mounting bolt
deflects upward during removal, raise axle by
adjusting the support jack. If the lower shock
absorber bolt deflects downward during removal,
lower the axle by adjusting the support jack.
(3) Remove the shock absorber lower mounting
bolt.
(4) While holding shock absorber, remove the
shock absorber upper mounting bolt and shock
absorber.
DISASSEMBLY - SHOCK ABSORBER (UPPER
BUSHING)
NOTE: This procedure applies to load-leveling
shock absorbers only.
(1) Remove the shock absorber from the vehicle.
(2) Install the Receiver, Special Tool 8526-1, into
the cup of the Ball Joint Press, Special Tool C-4212F,and tighten the set screw. Install the Driver, Special
Tool 8526-2, on the tip of the Ball Joint Press screw
drive as shown (Fig. 22).
NOTE: It works well to place the Ball Joint Press,
Special Tool C-4212F, in a bench vise as shown
(Fig. 22) to perform this procedure.
(3) Place the shock absorber upper mounting eye
in the Receiver so the notch in the Receiver clears
the shock absorber body (Fig. 23).
(4) Tighten the screw drive until the Driver con-
tacts the outer circumference of the bushing evenly
(Fig. 23). Continue to tighten the screw drive until
the bushing is pressed completely out of the shock
absorber eye and into the Receiver.
(5) Back off the screw drive and remove the bush-
ing from the Receiver.
Fig. 22 Special Tools Positioned For Removal
1 - SCREW DRIVE
Fig. 23 Removing Bushing From Shock Absorber
1 - SCREW DRIVE
2 - SHOCK ABSORBER
3 - NOTCH
RSREAR SUSPENSION2-37

DIFFERENTIAL & DRIVELINE
TABLE OF CONTENTS
page page
HALF SHAFT - FRONT.....................1
HALF SHAFT - REAR.....................13PROPELLER SHAFT.....................21
REAR DRIVELINE MODULE................23
HALF SHAFT - FRONT
TABLE OF CONTENTS
page page
HALF SHAFT - FRONT
DESCRIPTION..........................1
DIAGNOSIS AND TESTING - HALF SHAFT.....1
REMOVAL.............................2
INSTALLATION..........................4
SPECIFICATIONS - HALF SHAFT - FRONT....6CV BOOT - INNER
REMOVAL.............................6
INSTALLATION..........................6
CV BOOT - OUTER
REMOVAL.............................10
INSTALLATION.........................10
HALF SHAFT - FRONT
DESCRIPTION
All vehicles use an unequal length half shaft sys-
tem (Fig. 1).
The left half shaft uses a tuned rubber damper
weight. When replacing the left half shaft, be sure
the replacement half shaft has the same damper
weight as the original.
All half shaft assemblies use the same type of
inner and outer joints. The inner joint of both half
shaft assemblies is a tripod joint, and the outer joint
of both half shaft assemblies is a Rzeppa joint. Both
tripod joints and Rzeppa joints are true constant
velocity (CV) joint assemblies. The inner tripod joint
allows for the changes in half shaft length through
the jounce and rebound travel of the front suspen-
sion.
On vehicles equipped with ABS brakes, the outer
CV joint is equipped with a tone wheel used to deter-
mine vehicle speed for ABS brake operation.
The inner tripod joint of both half shafts is splined
into the transaxle side gears. The inner tripod joints
are retained in the side gears of the transaxle using
a snap ring located in the stub shaft of the tripod
joint. The outer CV joint has a stub shaft that is
splined into the wheel hub and retained by a steel
hub nut.
DIAGNOSIS AND TESTING - HALF SHAFT
VEHICLE INSPECTION
(1) Check for grease in the vicinity of the inboard
tripod joint and outboard CV joint; this is a sign of
inner or outer joint seal boot or seal boot clamp dam-
age.
NOISE AND/OR VIBRATION IN TURNS
A clicking noise and/or a vibration in turns could
be caused by one of the following conditions:
²Damaged outer CV or inner tripod joint seal
boot or seal boot clamps. This will result in the loss
and/or contamination of the joint grease, resulting in
inadequate lubrication of the joint.
²Noise may also be caused by another component
of the vehicle coming in contact with the half shafts.
CLUNKING NOISE DURING ACCELERATION
This noise may be a result of one of the following
conditions:
²A torn seal boot on the inner or outer joint of the
half shaft assembly.
²A loose or missing clamp on the inner or outer
joint of the half shaft assembly.
²A damaged or worn half shaft CV joint.
RSDIFFERENTIAL & DRIVELINE3-1

SHUDDER OR VIBRATION DURING ACCELERATION
This problem could be a result of:
²A worn or damaged half shaft inner tripod joint.
²A sticking tripod joint spider assembly (inner tri-
pod joint only).
²Improper wheel alignment. (Refer to 2 - SUS-
PENSION/WHEEL ALIGNMENT - STANDARD
PROCEDURE)
VIBRATION AT HIGHWAY SPEEDS
This problem could be a result of:
²Foreign material (mud, etc.) packed on the back-
side of the wheel(s).
²Out of balance tires or wheels. (Refer to 22 -
TIRES/WHEELS - STANDARD PROCEDURE)
²Improper tire and/or wheel runout. (Refer to 22 -
TIRES/WHEELS - DIAGNOSIS AND TESTING)
REMOVAL
(1) Raise vehicle.
(2) Remove the cotter pin and nut lock (Fig. 2)
from the end of the half shaft.
(3) Remove the wheel and tire assembly from the
vehicle. (Refer to 22 - TIRES/WHEELS - REMOVAL)
(4) Remove the wave washer (Fig. 3) from the end
of the half shaft.(5) With the vehicle's brakes applied to keep hub
from turning,loosen and removethe half shaft
nut.
(6) Remove the two front disc brake caliper
adapter to steering knuckle attaching bolts (Fig. 4).
Fig. 1 Unequal Length Half Shaft System
1 - STUB AXLE 8 - OUTER C/V JOINT
2 - OUTER C/V JOINT 9 - RIGHT HALFSHAFT
3 - OUTER C/V JOINT BOOT 10 - INNER TRIPOD JOINT BOOT
4 - TUNED RUBBER DAMPER WEIGHT 11 - INNER TRIPOD JOINT
5 - INTERCONNECTING SHAFT 12 - INNER TRIPOD JOINT
6 - OUTER C/V JOINT BOOT 13 - INNER TRIPOD JOINT BOOT
7 - STUB AXLE 14 - INTERCONNECTING SHAFT LEFT HALFSHAFT
Fig. 2 Half Shaft Retaining Nut
1 - HUB/BEARING
2 - NUT LOCK
3 - COTTER PIN
4 - STUB AXLE
3 - 2 HALF SHAFT - FRONTRS
HALF SHAFT - FRONT (Continued)

HALF SHAFT - REAR
TABLE OF CONTENTS
page page
HALF SHAFT - REAR
DESCRIPTION.........................13
DIAGNOSIS AND TESTING - HALF SHAFT....13
REMOVAL.............................13
INSTALLATION.........................14SPECIFICATIONS - HALF SHAFT - FRONT . . . 15
CV BOOT - INNER/OUTER
REMOVAL.............................15
INSTALLATION.........................17
HALF SHAFT - REAR
DESCRIPTION
The inner and outer joints of both half shaft
assemblies are tripod joints. The tripod joints are
true constant velocity (CV) joint assemblies, which
allow for the changes in half shaft length through
the jounce and rebound travel of the rear suspension.
On vehicles equipped with ABS brakes, the outer
CV joint is equipped with a tone wheel used to deter-
mine vehicle speed for ABS brake operation.
The inner tripod joint of both half shafts is bolted
rear differential assembly's output flanges. The outer
CV joint has a stub shaft that is splined into the
wheel hub and retained by a steel hub nut.
DIAGNOSIS AND TESTING - HALF SHAFT
VEHICLE INSPECTION
(1) Check for grease in the vicinity of the inboard
tripod joint and outboard CV joint; this is a sign of
inner or outer joint seal boot or seal boot clamp dam-
age.
NOISE AND/OR VIBRATION IN TURNS
A clicking noise and/or a vibration in turns could
be caused by one of the following conditions:
²Damaged outer CV or inner tripod joint seal
boot or seal boot clamps. This will result in the loss
and/or contamination of the joint grease, resulting in
inadequate lubrication of the joint.
²Noise may also be caused by another component
of the vehicle coming in contact with the half shafts.
CLUNKING NOISE DURING ACCELERATION
This noise may be a result of one of the following
conditions:
²A torn seal boot on the inner or outer joint of the
half shaft assembly.
²A loose or missing clamp on the inner or outer
joint of the half shaft assembly.
²A damaged or worn half shaft CV joint.
SHUDDER OR VIBRATION DURING ACCELERATION
This problem could be a result of:
²A worn or damaged half shaft inner tripod joint.
²A sticking tripod joint spider assembly (inner tri-
pod joint only).
²Improper wheel alignment. (Refer to 2 - SUS-
PENSION/WHEEL ALIGNMENT - STANDARD
PROCEDURE)
VIBRATION AT HIGHWAY SPEEDS
This problem could be a result of:
²Foreign material (mud, etc.) packed on the back-
side of the wheel(s).
²Out of balance tires or wheels. (Refer to 22 -
TIRES/WHEELS - STANDARD PROCEDURE)
²Improper tire and/or wheel runout. (Refer to 22 -
TIRES/WHEELS - DIAGNOSIS AND TESTING)
REMOVAL
(1) Lift vehicle on hoist so that the wheels hang
freely.
(2) Remove rear wheel.
(3) Remove cotter pin, nut lock, and spring washer
(Fig. 1).
Fig. 1 Cotter Pin, Nut Lock, And Spring Washer
1 - HUB NUT
2 - NUT LOCK
3 - COTTER PIN
4 - SPRING WASHER
RSHALF SHAFT - REAR3-13

REAR DRIVELINE MODULE
TABLE OF CONTENTS
page page
REAR DRIVELINE MODULE
DESCRIPTION.........................23
OPERATION...........................23
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - REAR
DRIVELINE MODULE NOISE.............24
DIAGNOSIS AND TESTING - REAR
DRIVELINE MODULE OPERATION........26
REMOVAL.............................26
DISASSEMBLY.........................27
ASSEMBLY............................29
INSTALLATION.........................33
SPECIFICATIONS - REAR DRIVELINE
MODULE............................34
SPECIAL TOOLS.......................34
BI-DIRECTIONAL OVERRUNNING CLUTCH
DESCRIPTION.........................34
OPERATION...........................36
DIFFERENTIAL ASSEMBLY
DESCRIPTION.........................39OPERATION...........................39
FLUID - DIFFERENTIAL ASSEMBLY
STANDARD PROCEDURE - DIFFERENTIAL
ASSEMBLY FLUID CHANGE.............40
FLUID - OVERRUNNING CLUTCH HOUSING
STANDARD PROCEDURE - OVERRUNNING
CLUTCH HOUSING FLUID CHANGE.......41
VISCOUS COUPLER
DESCRIPTION.........................41
OPERATION...........................42
TORQUE ARM
REMOVAL.............................44
INSTALLATION.........................44
INPUT FLANGE SEAL
REMOVAL.............................44
INSTALLATION.........................45
OUTPUT FLANGE SEAL
REMOVAL.............................45
INSTALLATION.........................46
REAR DRIVELINE MODULE
DESCRIPTION
The rear driveline module assembly (Fig. 1) con-
sists of four main components:
²Bi-Directional Overrunning Clutch (BOC)
²Viscous Coupling
²Differential Assembly
²Torque Arm
The viscous coupling and bi-directional overrun-
ning clutch are contained within an overrunning
clutch housing, which fastens to the differential
assembly. The overrunning clutch housing and differ-
ential assembly have unique fluid sumps, each
requiring their own type and capacity of fluid. The
overrunning clutch housing requires MopartATF+4
(Automatic Transmission FluidÐType 9602) or equiv-
alent. The differential assembly requires Mopart
80W-90 Gear and Axle Lubricant.
Driveline module service is limited to the following
components:
²Differential Assembly (serviced only as assem-
bly)
²Viscous Coupling
²Bi-Directional Overrunning Clutch (BOC)
²Overrunning Clutch Housing²Seals (Input Flange, Output Flange, Overrun-
ning Clutch Housing O-rings)
²Input Flange/Shield
²Torque Arm
²Vents
²Fasteners
OPERATION
The primary benefits of All Wheel Drive are:
²Superior straight line acceleration, and corner-
ing on all surfaces
²Better traction and handling under adverse con-
ditions, resulting in improved hill climbing ability
and safer driving.
The heart of the system is an inter-axle viscous
coupling. The vehicle retains predominantly front-
wheel drive characteristics, but the All Wheel Drive
capability takes effect when the front wheels start to
slip. Under normal level road, straight line driving,
100% of the torque is allocated to the front wheels.
The viscous coupling controls and distributes torque/
power to the rear wheels. The viscous coupling trans-
mits torque to the rear wheels in proportion of the
amount of the slippage at the front wheels. Thais
variable torque distribution is automatic with no
driver inputs required. The coupling is similar to a
multi-plate clutch. It consists of a series of closely
spaced discs, which are alternately connected to the
RSREAR DRIVELINE MODULE3-23

START-UP CYCLE
When the ignition is turned on, a popping sound
and a slight brake pedal movement may be noticed.
The ABS warning lamp will also be on for up to 5
seconds after the ignition is turned on. When the
vehicle is first driven off, a humming may be heard
or felt by the driver at approximately 20±40 kph
(12±25 mph). All of these conditions are a normal
function of ABS as the system is performing a diag-
nosis check.
PREMATURE ABS CYCLING
Symptoms of premature ABS cycling include: click-
ing sounds from the solenoid valves; pump/motor
running; and pulsations in the brake pedal. Prema-
ture ABS cycling can occur at any braking rate of the
vehicle and on any type of road surface. Neither the
red BRAKE warning lamp, nor the amber ABS warn-
ing lamp, illuminate and no fault codes are stored in
the CAB.
Premature ABS cycling is a condition that needs to
be correctly assessed when diagnosing problems with
the antilock brake system. It may be necessary to use
a DRB scan tool to detect and verify premature ABS
cycling.
Check the following common causes when diagnos-
ing premature ABS cycling: damaged tone wheels;
incorrect tone wheels; damaged steering knuckle
wheel speed sensor mounting bosses; loose wheel
speed sensor mounting bolts; excessive tone wheel
runout; or an excessively large tone wheel-to-wheel
speed sensor air gap. Give special attention to these
components when diagnosing a vehicle exhibiting
premature ABS cycling.
After diagnosing the defective component, repair or
replace it as required. When the component repair or
replacement is completed, test drive the vehicle to
verify that premature ABS cycling has been cor-
rected.
OPERATION - ELECTRONIC VARIABLE BRAKE
PROPORTIONING
Upon entry into EVBP the inlet valve for the rear
brake circuit is switched on so that the fluid supply
from the master cylinder is shut off. In order to
decrease the rear brake pressure, the outlet valve for
the rear brake circuit is pulsed. This allows fluid to
enter the low pressure accumulator (LPA) in the
hydraulic control unit (HCU) resulting in a drop in
fluid pressure to the rear brakes. In order to increase
the rear brake pressure, the outlet valve is switched
off and the inlet valve is pulsed. This increases the
pressure to the rear brakes. This back-and-forth pro-
cess will continue until the required slip difference is
obtained. At the end of EVBP braking (brakes
released) the fluid in the LPA drains back to themaster cylinder by switching on the outlet valve and
draining through the inlet valve check valve. At the
same time the inlet valve is switched on in case of
another brake application.
The EVBP will remain functional during many
ABS fault modes. If both the red BRAKE and amber
ABS warning indicators are illuminated, the EVBP
may not be functioning.
OPERATION - TRACTION CONTROL SYSTEM
The traction control module monitors wheel speed.
During acceleration, if the module detects front
(drive) wheel slip and the brakes are not applied, the
module enters traction control mode. Traction control
operation proceeds in the following order:
(1) Close the normally open isolation valves.
(2) Start the pump/motor and supply volume and
pressure to the front (drive) hydraulic circuit. (The
pump/motor runs continuously during traction con-
trol operation.)
(3) Open and close the build and decay valves to
maintain minimum wheel slip and maximum trac-
tion.
The cycling of the build and decay valves during
traction control is similar to that during antilock
braking, except the valves work to control wheel spin
by applying the brakes, whereas the ABS function is
to control wheel skid by releasing the brakes.
If the brakes are applied at anytime during a trac-
tion control cycle, the brake lamp switch triggers the
controller to switch off traction control.
HYDRAULIC SHUTTLE VALVES
Two pressure relief hydraulic shuttle valves allow
pressure and volume to return to the master cylinder
reservoir when not consumed by the build and decay
valves. These valves are necessary because the
pump/motor supplies more volume than the system
requires.
TRACTION CONTROL LAMP
The traction control system is enabled at each igni-
tion cycle. It may be turned off by depressing the
Traction Control Off switch button when the ignition
is in the ON position. The traction control function
lamp (TRAC OFF) illuminates immediately upon
depressing the button.
The traction control function lamp illuminates dur-
ing a traction control cycle, displaying TRAC.
If the CAB calculates that the brake temperatures
are high, the traction control system becomes inoper-
ative until a time-out period has elapsed. During this
ªthermo-protection mode,º the traction control func-
tion lamp illuminates TRAC OFF; note that no trou-
ble code is registered.
RSBRAKES - ABS5-77
BRAKES - ABS (Continued)

CONDITION POSSIBLE CAUSE CORRECTION
ENGINE LOSS OF POWER 1. Dirty or incorrectly gapped plugs. 1. Clean plugs and set gap.
2. Contamination in fuel system. 2. Clean system and replace fuel
filter.
3. Faulty fuel pump. 3. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
4. Incorrect valve timing. 4. Correct valve timing.
5. Leaking cylinder head gasket. 5. Replace cylinder head gasket.
6. Low compression. 6. Test compression of each
cylinder.
7. Burned, warped, or pitted valves. 7. Replace valves.
8. Plugged or restricted exhaust
system.8. Perform exhaust restriction test.
(Refer to 11 - EXHAUST SYSTEM -
DIAGNOSIS AND TESTING) Install
new parts, as necessary.
9. Faulty ignition coil(s). 9. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
ENGINE MISSES ON
ACCELERATION1. Dirty or incorrectly gapped spark
plugs.1. Clean spark plugs and set gap.
2. Contamination in Fuel System. 2. Clean fuel system and replace
fuel filter.
3. Burned, warped, or pitted valves. 3. Replace valves.
4. Faulty ignition coil(s). 4. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
ENGINE MISSES AT HIGH SPEED 1. Dirty or incorrect spark plug gap. 1. Clean spark plugs and set gap.
2. Faulty ignition coil(s). 2. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
3. Dirty fuel injector(s). 3. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
4. Contamination in fuel system. 4. Clean system and replace fuel
filter.
RSENGINE 2.4L9-5
ENGINE 2.4L (Continued)

CONDITION POSSIBLE CAUSE CORRECTION
ENGINE LOSS OF POWER 1. Dirty or incorrectly gapped plugs. 1. Clean plugs and set gap.
2. Contamination in fuel system. 2. Clean system and replace fuel
filter.
3. Faulty fuel pump. 3. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
4. Incorrect valve timing. 4. Correct valve timing.
5. Leaking cylinder head gasket. 5. Replace cylinder head gasket.
6. Low compression. 6. Test compression of each
cylinder.
7. Burned, warped, or pitted valves. 7. Replace valves.
8. Plugged or restricted exhaust
system.8. Perform exhaust restriction test.
(Refer to 11 - EXHAUST SYSTEM -
DIAGNOSIS AND TESTING) Install
new parts, as necessary.
9. Faulty ignition coil(s). 9. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
ENGINE MISSES ON
ACCELERATION1. Dirty or incorrectly gapped spark
plugs.1. Clean spark plugs and set gap.
2. Contamination in Fuel System. 2. Clean fuel system and replace
fuel filter.
3. Burned, warped, or pitted valves. 3. Replace valves.
4. Faulty ignition coil(s). 4. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
ENGINE MISSES AT HIGH SPEED 1. Dirty or incorrect spark plug gap. 1. Clean spark plugs and set gap.
2. Faulty ignition coil(s). 2. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
3. Dirty fuel injector(s). 3. Test and replace as necessary.
(Refer to Appropriate Diagnostic
Information)
4. Contamination in fuel system. 4. Clean system and replace fuel
filter.
RSENGINE 3.3/3.8L9-79
ENGINE 3.3/3.8L (Continued)

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

²All monitored components (refer to the Emission
section for On-Board Diagnostics).
The PCM compares the upstream and downstream
heated oxygen sensor inputs to measure catalytic
convertor efficiency. If the catalyst efficiency drops
below the minimum acceptable percentage, the PCM
stores a diagnostic trouble code in memory, after 2
trips.
During certain idle conditions, the PCM may enter
a variable idle speed strategy. During variable idle
speed strategy the PCM adjusts engine speed based
on the following inputs.
²A/C status
²Battery voltage
²Battery temperature or Calculated Battery Tem-
perature
²Engine coolant temperature
²Engine run time
²Inlet/Intake air temperature
²Vehicle mileage
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in Throttle Position sensor
output voltage or MAP sensor output voltage as a
demand for increased engine output and vehicle
acceleration. The PCM increases injector pulse width
in response to increased fuel demand.
²Wide Open Throttle-open loop
DECELERATION MODE
This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
²A/C status
²Battery voltage
²Inlet/Intake air temperature
²Engine coolant temperature
²Crankshaft position (engine speed)
²Exhaust gas oxygen content (upstream heated
oxygen sensor)
²Knock sensor
²Manifold absolute pressure
²Throttle position sensor
²IAC motor (solenoid) control changes in response
to MAP sensor feedback
The PCM may receive a closed throttle input from
the Throttle Position Sensor (TPS) when it senses an
abrupt decrease in manifold pressure. This indicates
a hard deceleration (Open Loop). In response, the
PCM may momentarily turn off the injectors. This
helps improve fuel economy, emissions and engine
braking.
WIDE-OPEN-THROTTLE MODE
This is an OPEN LOOP mode. During wide-open-
throttle operation, the following inputs are used by
the PCM:
²Inlet/Intake air temperature
²Engine coolant temperature
²Engine speed
²Knock sensor
²Manifold absolute pressure
²Throttle position
When the PCM senses a wide-open-throttle condi-
tion through the Throttle Position Sensor (TPS) it de-
energizes the A/C compressor clutch relay. This
disables the air conditioning system and disables
EGR (if equipped).
The PCM adjusts injector pulse width to supply a
predetermined amount of additional fuel, based on
MAP and RPM.
IGNITION SWITCH OFF MODE
When the operator turns the ignition switch to the
OFF position, the following occurs:
²All outputs are turned off, unless 02 Heater
Monitor test is being run. Refer to the Emission sec-
tion for On-Board Diagnostics.
²No inputs are monitored except for the heated
oxygen sensors. The PCM monitors the heating ele-
ments in the oxygen sensors and then shuts down.
FUEL CORRECTION or ADAPTIVE MEMORIES
DESCRIPTION
In Open Loop, the PCM changes pulse width with-
out feedback from the O2 Sensors. Once the engine
warms up to approximately 30 to 35É F, the PCM
goes into closed loopShort Term Correctionand
utilizes feedback from the O2 Sensors. Closed loop
Long Term Adaptive Memoryis maintained above
170É to 190É F unless the PCM senses wide open
throttle. At that time the PCM returns to Open Loop
operation.
OPERATION
Short Term
The first fuel correction program that begins func-
tioning is the short term fuel correction. This system
corrects fuel delivery in direct proportion to the read-
ings from the Upstream O2 Sensor.
The PCM monitors the air/fuel ratio by using the
input voltage from the O2 Sensor. When the voltage
reaches its preset high or low limit, the PCM begins
to add or remove fuel until the sensor reaches its
switch point. The short term corrections then begin.
The PCM makes a series of quick changes in the
injector pulse-width until the O2 Sensor reaches its
14 - 20 FUEL INJECTIONRS
FUEL INJECTION (Continued)