1996 CHRYSLER VOYAGER heating

plugs.Ash encrusted spark plugs can be cleaned
and reused.
HIGH SPEED MISS
When replacing spark plugs because of a high
speed miss condition;wide open throttle opera-
tion should be avoided for approximately 80 km
(50 miles) after installation of new plugs.This
will allow deposit shifting in the combustion chamber
to take place gradually and avoid plug destroying
splash fouling shortly after the plug change.
ELECTRODE GAP BRIDGING
Loose deposits in the combustion chamber can
cause electrode gap bridging. The deposits accumu-
late on the spark plugs during continuous stop-
and-go driving. When the engine is suddenly
subjected to a high torque load, the deposits partially
liquefy and bridge the gap between the electrodes
(Fig. 25). This short circuits the electrodes.Spark
plugs with electrode gap bridging can be
cleaned and reused.
SCAVENGER DEPOSITS
Fuel scavenger deposits may be either white or yel-
low (Fig. 26). They may appear to be harmful, but
are a normal condition caused by chemical additives
in certain fuels. These additives are designed to
change the chemical nature of deposits and decrease
spark plug misfire tendencies. Notice that accumula-
tion on the ground electrode and shell area may be
heavy but the deposits are easily removed.Spark
plugs with scavenger deposits can be consid-
ered normal in condition, cleaned and reused.
CHIPPED ELECTRODE INSULATOR
A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation also can separate the insulator
from the center electrode (Fig. 27).Spark plugs
with chipped electrode insulators must be
replaced.
PREIGNITION DAMAGE
Excessive combustion chamber temperature can
cause preignition damage. First, the center electrode
dissolves and the ground electrode dissolves some-
what later (Fig. 28). Insulators appear relatively
deposit free. Determine if the spark plugs are the
correct type, as specified on the VECI label, or if
other operating conditions are causing engine over-
heating.
SPARK PLUG OVERHEATING
Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
Fig. 24 Oil or Ash Encrusted
Fig. 25 Electrode Gap Bridging
Fig. 26 Scavenger Deposits
8D - 12 IGNITION SYSTEMNS
DIAGNOSIS AND TESTING (Continued)

29). The increase in electrode gap will be consider-
ably in excess of 0.001 in per 1000 miles of operation.
This suggests that a plug with a cooler heat range
rating should be used. Over advanced ignition tim-
ing, detonation and cooling system malfunctions also
can cause spark plug overheating.
THROTTLE POSITION SENSOR
To perform a complete test of the this sensor and
its circuitry, refer to the DRB scan tool and appropri-
ate Powertrain Diagnostics Procedures manual. To
test the throttle position sensor only, refer to the fol-
lowing:
The Throttle Position Sensor (TPS) can be tested
with a digital voltmeter (DVM). The center terminal
of the sensor is the output terminal. One of the other
terminals is a 5 volt supply and the remaining ter-
minal is ground.
Connect the DVM between the center and sensor
ground terminal. Refer to Group 8W - Wiring Dia-
grams for correct pinout.With the ignition switch in the ON position, check
the output voltage at the center terminal wire of the
connector. Check the output voltage at idle and at
Wide-Open-Throttle (WOT). At idle, TPS output volt-
age should be approximately 0.38 volts to 1.2 volts.
At wide open throttle, TPS output voltage should be
approximately 3.1 volts to 4.4 volts. The output volt-
age should gradually increase as the throttle plate
moves slowly from idle to WOT.
Check for spread terminals at the sensor and PCM
connections before replacing the TPS.
SERVICE PROCEDURES
SPARK PLUG GAP ADJUSTMENT
Check the spark plug gap with a gap gauge. If the
gap is not correct, adjust it by bending the ground
electrode (Fig. 30).
CAUTION: The Platinum pads can be damaged dur-
ing the measurement of checking the gap if extreme
care is not used.
Refer to 3.3/3.8L Spark Plug Gap Measurment in
this section.
POWERTRAIN CONTROL MODULE
REMOVAL
(1) Disconnect both cables from battery, negative
cable first.
(2) Remove 2 screws holding Power Distribution
Center (PDC) to bracket (Fig. 31).
(3) Remove heat shield from battery (Fig. 32).
(4) Remove nut and clamp holding battery to bat-
tery tray (Fig. 33).
(5) Remove battery from vehicle.
(6) Rotate PDC toward center of vehicle to remove
from rear bracket (Fig. 34).
Fig. 27 Chipped Electrode Insulator
Fig. 28 Preignition Damage
Fig. 29 Spark Plug Overheating
NSIGNITION SYSTEM 8D - 13
DIAGNOSIS AND TESTING (Continued)

(2) Inspect BCM connectors and wires for proper
connection. If OK, replace BCM for tone condition.
DOME LAMP ON CHIME
The dome lamp on chime will warn the driver that
the dome lamps have been left on.
With the ignition is OFF:
²Driver's door OPEN (door ajar switch is closed to
ground)
²Dome lamps are ON (dome lamp switch is closed
to ground),
The chime will sound continuously until driver's
door is closed, dome lamps tuned OFF or until the
battery protection time out of 15 minutes has
expired. Refer Group 8L, Lamps proper procedures.
Chime rate: 168 to 192 chimes per minute.
ENGINE TEMPERATURE CRITICAL CHIME
The engine temperature critical chime will warn
the driver that the vehicle's engine is overheating.
While monitoring the coolant temperature, the Pow-
ertrain Control Module (PCM) will send on the CCD
bus as engine temperature every 1.376 seconds to the
Body Control Module (BCM). The BCM calculates
engine temperature and determines if a warning
should occur. This feature is functional only with the
Ignition Switch in the Run/Start position.
When the engine temperature reaches 122ÉC
(252ÉF) the BCM will chime one tone and the engine
temperature lamp comes ON. The BCM turns OFF
the lamp when the engine temperature reaches
117ÉC (242ÉF). The BCM will chime continuously
when the engine temperature reaches 125ÉC (257ÉF).
The chime will turn OFF after four minutes or when
the temperature reaches 117ÉC (242ÉF), which ever
occurs first.
EXTERIOR LAMPS ON CHIME
The exterior lamp on chime will warn the driver
that the exterior lights have been left on.
With the ignition switch OFF:
²Driver's door is open (door ajar switch is closed
to ground)
²Parking lamps or headlamps ON (parking lamp
switch is closed to ground)
The chime will sound until lights are turned OFF,
driver's door closed or until the battery protection
time out of 3 minutes has expired.
Refer to Group 8L, Lamps, for proper service pro-
cedures. Chime rate: 168 to 192 chimes per minute.
To test the exterior lamps left on function:
²Turn ignition off
²Remove ignition key
²Turn exterior lamps on with driver's door open.
Chime should sound until lamps are turned off or
driver's door is closed.
KEY-IN IGNITION CHIME
The key-in ignition chime will act as a warning to
the driver that the ignition key has been left in the
ignition switch.
With the ignition switch is in OFF position ONLY:
²Driver's door is open/ajar (door ajar switch is
closed to ground)
²Key is in the ignition switch (key-in ignition
switch is closed to ground)
The chime will sound until one of the above condi-
tions is removed. Chime rate: 168 to 192 chimes per
minute.
To test the key-in ignition function, insert key into
the ignition and open driver's door. Do not turn igni-
tion ON. Chime should sound until key is removed
from ignition or driver's door is closed.
LOW OIL PRESSURE CHIME OPERATION
The low oil pressure chime will warn the driver
that the engine oil pressure is low. The oil pressure
switch, will close to ground during a low oil pressure
condition. The oil pressure lamp will illuminate in
the message center. The body control module will
monitor the oil pressure switch and signal a low oil
pressure condition. A continuous four minute warn-
ing chime will sound and the oil pressure lamp will
come ON when the following conditions are met:
²Ignition on and engine not cranking
²Engine running at 420 to 480 rpm for 10 sec-
onds
²Oil pressure switch closed to ground for (1 sec-
ond minimum, 2 seconds maximum)
Chime rate: 168 to 192 chimes per minute.
SEAT BELT CHIME
The seat belt chime will sound for 4 to 8 seconds,
when the ignition is turned on and the driver's seat
belt is not buckled (seat belt switch is closed to
ground). This is a reminder to the driver to buckle
the seat belt. The seat belt lamp is controlled by the
mechanical instrument cluster. The cluster will also
illuminate the seat belt warning lamp for 6 seconds.
Buckling the driver's seat belt before the time out
has expired will cause the chime to stop immediately.
Chime rate: 38 to 62 chimes per minute.
To test the seat belt warning system, the ignition
switch must be in the OFF position for 1 minute
before starting the test. Turn the ignition switch to
the on position with the driver's seat belt not buck-
led. The seat belt warning lamp should light and the
chime should sound 4 to 8 seconds.
SEAT BELT LAMP
The seat belt lamp in the instrument cluster sig-
nals the vehicle passengers to fasten their seat belts.
The seat belt lamp is illuminated directly by the
8U - 2 CHIME WARNING/REMINDER SYSTEMNS
DIAGNOSIS AND TESTING (Continued)

CHIME WARNING/REMINDER SYSTEM
CONTENTS
page page
GENERAL INFORMATION
INTRODUCTION........................ 1
DIAGNOSIS AND TESTING
CATALYST OVERHEAT WARNING CHIME.... 1
CHIME SYSTEM DIAGNOSIS.............. 1
DOME LAMP ON CHIME................. 2
ENGINE TEMPERATURE CRITICAL CHIME . . . 2EXTERIOR LAMPS ON CHIME............. 2
KEY-IN IGNITION CHIME................. 2
LOW OIL PRESSURE CHIME OPERATION . . . 2
SEAT BELT CHIME...................... 3
SEAT BELT LAMP...................... 3
TURN SIGNAL ON CHIME................ 3
WARNING LAMP ANNOUNCEMENT CHIME . . 3
GENERAL INFORMATION
INTRODUCTION
WARNING: ON VEHICLES EQUIPPED WITH AN
AIRBAG, REFER TO GROUP 8M, RESTRAINT SYS-
TEMS FOR SAFETY PRECAUTIONS AND WARN-
INGS TO OBSERVE WHEN SERVICING AIRBAG
RELATED COMPONENTS.
The chime system provides the driver with warn-
ing chimes for:
²Seat Belt
²Exterior Lamps ON
²Key-In Ignition
²Engine Temperature Critical
²Turn Signals ON
²Dome Lamp ON
²Low Oil Pressure
²High Speed Warning
²Warning Lamp Announcement
²Catalyst Overheating
The Chime Warning/Reminder System is diagnosed
using a scan tool (DRB). Refer to the proper Body
Diagnostic Procedures manual for testing procedures
and scan tool usage instructions.
DIAGNOSIS AND TESTING
CATALYST OVERHEAT WARNING CHIME
The Catalyst Overheat Warning Chime will act as
a warning to the driver that the vehicle's catalyst
has entered an overheat condition. The Powertrain
Control Module (PCM) will enable or disable this fea-
ture for the appropriate vehicles. Right hand drive
gas vehicles only. The Body Control Module (BCM)
will monitor the CCD bus for status and signal a cat-
alyst overheat condition with continuous warning
chime when the following conditions are met:²Ignition switch in the ON position
²Engine running at 420 to 480 rpm for 10 sec-
onds
²CCD status and with a chime rate of one chime
per second.
CHIME SYSTEM DIAGNOSIS
NO TONE WHEN IGNITION SWITCH IS
TURNED ON AND DRIVER'S SEAT BELT IS
NOT BUCKLED.
(1) Using a scan tool (DRB), check for tone in any
other function.
(2) Using a voltmeter, check for voltage:
(a) Pin 9 of the internal 32 way connector of the
BCM for battery feed.
(b) Pin 8 of the internal 32 way connector of the
BCM for ignition feed.
(c) If voltage OK, go to step Step 3
(d) If NO voltage repair as necessary. Refer to
Group 8W, Wiring Diagrams for component loca-
tions and circuit information.
(3) Check driver's seat belt buckle switch input for
a closed circuit when not buckled. If input not seen,
look for open in wiring or switch. The switch is
grounded when belt is not buckled.
(4) Repair as necessary.
NO FASTEN SEAT BELT LAMP WHEN
IGNITION SWITCH IS TURNED ON.
(1) Check for burned out lamp.
(2) Using a voltmeter check for voltage:
(a) Pin 2 of the mechanical instrument cluster
for battery feed.
(b) Pin 11 of the mechanical instrument cluster
for ignition voltage.
(3) Repair as necessary.
NS/GSCHIME WARNING/REMINDER SYSTEM 8U - 1

FASTEN SEAT BELT LAMP OR TONE
CONTINUES FOR MORE THAN 10 SECONDS
AFTER SEAT BELTS ARE FASTENED AND
DRIVER'S DOOR IS CLOSED.
(1) Check left door ajar switch for no ground when
switch is depressed.
(a) If continuity replace door ajar switch.
(b) If NO continuity replace BCM for tone condi-
tion, or replace mechanical instrument panel for
lamp condition.
(c) Replace BCM for tone condition.
(d) Replace mechanical instrument cluster for
lamp condition.
NO TONE WHEN PARK OR HEADLAMPS ARE
ON AND DRIVER'S DOOR IS OPEN.
(1) Check left door ajar switch for good ground
when driver's door is open. Repair as necessary.
(2) Inspect BCM connectors and wires for proper
connection. If OK, replace BCM for tone condition.
DOME LAMP ON CHIME
The dome lamp on chime will warn the driver that
the dome lamps have been left on.
With the ignition is OFF:
²Driver's door OPEN (door ajar switch is closed to
ground)
²Dome lamps are ON (dome lamp switch is closed
to ground),
The chime will sound continuously until driver's
door is closed, dome lamps tuned OFF or until the
battery protection time out of 15 minutes has
expired. Refer Group 8L, Lamps proper procedures.
Chime rate: 168 to 192 chimes per minute.
ENGINE TEMPERATURE CRITICAL CHIME
The engine temperature critical chime will warn
the driver that the vehicle's engine is overheating.
While monitoring the coolant temperature, the Pow-
ertrain Control Module (PCM) will send on the CCD
bus as engine temperature every 1.376 seconds to the
Body Control Module (BCM). The BCM calculates
engine temperature and determines if a warning
should occur. This feature is functional only with the
Ignition Switch in the Run/Start position. On the
Diesel vehicles, the coolant temperature sensor is
read directly by the BCM.
When the engine temperature reaches 122ÉC
(252ÉF) or the diesel engine 112ÉC (234ÉF), the BCM
will chime one tone and the engine temperature lamp
comes ON. The BCM turns OFF the lamp when the
engine temperature reaches 117ÉC (242ÉF) or the die-
sel engine 108ÉC (226ÉF). The BCM will chime con-
tinuously when the engine temperature reaches
125ÉC (257ÉF) or diesel engine 116ÉC (241ÉF). The
chime will turn OFF after four minutes or when thetemperature reaches 117ÉC (242ÉF) or diesel engine
108ÉC (226ÉF), which ever occurs first.
EXTERIOR LAMPS ON CHIME
The exterior lamp on chime will warn the driver
that the exterior lights have been left on.
With the ignition switch OFF:
²Driver's door is open (door ajar switch is closed
to ground)
²Parking lamps or headlamps ON (parking lamp
switch is closed to ground)
The chime will sound until lights are turned OFF,
driver's door closed or until the battery protection
time out of 3 minutes has expired.
Refer to Group 8L, Lamps, for proper service pro-
cedures. Chime rate: 168 to 192 chimes per minute.
To test the exterior lamps left on function:
²Turn ignition off
²Remove ignition key
²Turn exterior lamps on with driver's door open.
Chime should sound until lamps are turned off or
driver's door is closed.
KEY-IN IGNITION CHIME
The key-in ignition chime will act as a warning to
the driver that the ignition key has been left in the
ignition switch.
With the ignition switch is in OFF position ONLY:
²Driver's door is open/ajar (door ajar switch is
closed to ground)
²Key is in the ignition switch (key-in ignition
switch is closed to ground)
The chime will sound until one of the above condi-
tions is removed. Chime rate: 168 to 192 chimes per
minute.
To test the key-in ignition function, insert key into
the ignition and open driver's door. Do not turn igni-
tion ON. Chime should sound until key is removed
from ignition or driver's door is closed.
LOW OIL PRESSURE CHIME OPERATION
The low oil pressure chime will warn the driver
that the engine oil pressure is low. The oil pressure
switch, will close to ground during a low oil pressure
condition. The oil pressure lamp will illuminate in
the message center. The body control module will
monitor the oil pressure switch and signal a low oil
pressure condition. A continuous four minute warn-
ing chime will sound and the oil pressure lamp will
come ON when the following conditions are met:
²Ignition on and engine not cranking
²Engine running at 420 to 480 rpm for 10 sec-
onds
²Oil pressure switch closed to ground for (1 sec-
ond minimum, 2 seconds maximum)
Chime rate: 168 to 192 chimes per minute.
8U - 2 CHIME WARNING/REMINDER SYSTEMNS/GS
DIAGNOSIS AND TESTING (Continued)

THROTTLE BODY....................... 64
THROTTLE POSITION SENSOR............ 65
UPSTREAM OXYGEN SENSOR............. 68
SPECIFICATIONS
TORQUE.............................. 72SPECIAL TOOLS
FUEL................................. 72
GENERAL INFORMATION
INTRODUCTION
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.
All inputs to the PCM are converted into signals.
The PCM can adapt its programming to meet chang-
ing 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 the primary inputs that determine injec-
tor pulse width.
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 PCMprogramming. Input from the oxygen (O2S) sensor is
not monitored during OPEN LOOP modes.
During CLOSED LOOP modes the PCM does mon-
itor the O2S sensor input. This input indicates to the
PCM whether or not the calculated injector pulse
width results in the ideal air/fuel ratio of 14.7 parts
air to 1 part fuel. By monitoring the exhaust oxygen
content through the O2S sensor, the PCM can fine
tune the injector pulse width. Fine tuning injector
pulse width allows the PCM to achieve optimum fuel
economy combined with low emissions.
The multi-port fuel injection system has the follow-
ing modes of operation:
²Ignition switch ON (zero RPM)
²Engine start-up
²Engine warm-up
²Cruise (Idle)
²Acceleration
²Deceleration
²Wide Open Throttle
²Ignition switch OFF
The engine start-up (crank), engine warm-up, and
wide open throttle modes are OPEN LOOP modes.
Under most operating conditions, the acceleration,
deceleration, and cruise modes,with the engine at
operating temperatureare CLOSED LOOP modes.
IGNITION SWITCH ON (ZERO RPM) MODE
When the multi-port fuel injection system is acti-
vated by the ignition switch, the following actions
occur:
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the coolant temperature sen-
sor and throttle position sensor input. The PCM mod-
ifies fuel strategy based on this input.
When the key is in the ON position and the engine
is not running (zero rpm), the Automatic Shutdown
(ASD) relay and fuel pump relay are not energized.
Therefore battery voltage is not supplied to the fuel
pump, ignition coil, fuel injectors or oxygen sensor
heating element.
ENGINE START-UP MODE
This is an OPEN LOOP mode. The following
actions occur when the starter motor is engaged.
If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the ASD relay and fuel pump relay. These relays sup-
ply battery voltage to the fuel pump, fuel injectors,
14 - 30 FUEL SYSTEMNS
SPECIFICATIONS (Continued)

ignition coil, and oxygen sensor heating element. If
the PCM does not receive the camshaft position sen-
sor and crankshaft position sensor signals within
approximately one second, it de-energizes the ASD
relay and fuel pump relay.
The PCM energizes all injectors until it determines
crankshaft position from the camshaft position sen-
sor and crankshaft position sensor signals. The PCM
determines crankshaft position within 1 engine revo-
lution.
After determining crankshaft position, the PCM
begins energizing the injectors in sequence. The PCM
adjusts injector pulse width and controls injector syn-
chronization by turning the individual ground paths
to the injectors On and Off.
When the engine idles within664 RPM of its tar-
get RPM, the PCM compares current MAP sensor
value with the atmospheric pressure value received
during the Ignition Switch On (zero RPM) mode. If
the PCM does not detect a minimum difference
between the two values, it sets a MAP diagnostic
trouble code into memory.
Once the ASD and fuel pump relays have been
energized, the PCM:
²Determines injector pulse width based on engine
coolant temperature, MAP and the number of engine
revolutions since cranking was initiated.
²Monitors the engine coolant temperature sensor,
camshaft position sensor, crankshaft position sensor,
MAP sensor, and throttle position sensor to deter-
mine correct ignition timing.
ENGINE WARM-UP MODE
This is a OPEN LOOP mode. The following inputs
are received by the PCM:
²Engine coolant temperature
²Manifold absolute pressure
²Engine speed (crankshaft position sensor)
²Throttle position
²A/C switch
²Battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts ignition timing and engine idle
speed. Engine idle speed is adjusted through the idle
air control motor.
CRUISE OR IDLE MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising speed the
following inputs are received by the PCM:²Engine coolant temperature
²Manifold absolute pressure
²Engine speed (crankshaft position sensor)
²Throttle position
²Exhaust gas oxygen content
²A/C control positions
²Battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off.
The PCM adjusts engine idle speed and ignition
timing. The PCM adjusts the air/fuel ratio according
to the oxygen content in the exhaust gas.
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
DECELERATION MODE
This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
²Engine coolant temperature
²Manifold absolute pressure
²Engine speed
²Throttle position
²Exhaust gas oxygen content
²A/C control positions
²Battery voltage
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. The PCM may reduce injector
pulse width or the number of injectors firing per
engine revolution. This helps maintain better control
of the air/fuel mixture (as sensed through the O2S
sensor).
WIDE OPEN THROTTLE (WOT) MODE
This is an OPEN LOOP mode. During WOT oper-
ation, the following inputs are received by the PCM:
²Engine coolant temperature
²Manifold absolute pressure
²Engine speed
²Throttle position
When the PCM senses WOT condition through the
Throttle Position Sensor (TPS) it will:
²De-energize the air conditioning relay. This dis-
ables the air conditioning system.
The exhaust gas oxygen content input is not
accepted by the PCM during WOT operation. The
PCM will adjust injector pulse width to supply a pre-
determined amount of additional fuel.
NSFUEL SYSTEM 14 - 31
GENERAL INFORMATION (Continued)

²Engine coolant temperature
²Engine speed (crankshaft position sensor)
²Intake air temperature (2.4L only)
²Manifold absolute pressure
²Throttle position
²Transaxle gear selection (park/neutral switch)
The PCM also adjusts engine idle speed through
the idle air control motor based on the following
inputs.
²Air conditioning select switch head pressure
²Brake switch
²Engine coolant temperature
²Engine speed (crankshaft position sensor)
²Manifold absolute pressure
²Throttle position
²Transaxle gear selection (park/neutral switch)
²Vehicle distance (speed)
The Automatic Shutdown (ASD) and fuel pump
relays are located in the Power Distribution Center
(PDC).
The camshaft position sensor (distributor pick-up
signal 3.0L) and crankshaft position sensor signals
are sent to the PCM. If the PCM does not receive
both signals within approximately one second of
engine cranking, it deactivates the ASD relay and
fuel pump relay. When these relays are deactivated,
power is shut off to the fuel injectors, ignition coil,
oxygen sensor heating element and fuel pump.
The PCM contains a voltage converter that
changes battery voltage to a regulated 8.0 volts to
power the camshaft position sensor, crankshaft posi-
tion sensor and vehicle speed sensor. The PCM also
provides a 5.0 volt supply for the manifold absolute
pressure sensor, throttle position sensor and engine
coolant temperature sensor.
AIR CONDITIONING PRESSURE TRANSDUCERÐ
PCM INPUT
The Powertrain Control Module (PCM) monitors
the A/C compressor discharge (high side) pressure
through the air conditioning pressure transducer.
The transducer supplies an input to the PCM. The
PCM engages the A/C compressor clutch if pressure
is sufficient for A/C system operation.
AIR CONDITIONING SWITCH SENSEÐPCM INPUT
When the air conditioning or defrost switch is put
in the ON position and the low pressure switch, com-
bination valve, and high pressure switch close, the
PCM receives an A/C input. After receiving this
input, the PCM activates the A/C compressor clutch
by grounding the A/C clutch relay. The PCM also
adjusts idle speed to a scheduled RPM to compensate
for increased engine load.
AUTOMATIC SHUTDOWN (ASD) SENSEÐPCM
INPUT
The ASD sense circuit informs the PCM when the
ASD relay energizes. A 12 volt signal at this input
indicates to the PCM that the ASD has been acti-
vated. This input is used only to sense that the ASD
relay is energized.
When energized, the ASD relay supplies battery
voltage to the fuel injectors, ignition coils and the
heating element in each oxygen sensor. If the PCM
does not receive 12 volts from this input after
grounding the ASD relay, it sets a Diagnostic Trouble
Code (DTC).
BATTERY VOLTAGEÐPCM INPUT
The PCM monitors the battery voltage input to
determine fuel injector pulse width and generator
field control.
If battery voltage is low the PCM will increase
injector pulse width (period of time that the injector
is energized).
BRAKE SWITCHÐPCM INPUT
When the brake switch is activated, the PCM
receives an input indicating that the brakes are
being applied. After receiving this input the PCM
maintains idle speed to a scheduled RPM through
control of the idle air control motor. The brake switch
is mounted on the brake pedal support bracket.
CAMSHAFT POSITION SENSORÐPCM INPUT
The PCM determines fuel injection synchronization
and cylinder identification from inputs provided by
the camshaft position sensor and crankshaft position
sensor. From the two inputs, the PCM determines
crankshaft position.
3.3/3.8L
The sensor generates pulses as groups of notches
on the camshaft sprocket pass underneath it (Fig. 2).
The PCM keeps track of crankshaft rotation and
identifies each cylinder by the pulses generated by
the notches on the camshaft sprocket. Four crank-
shaft pulses follow each group of camshaft pulses.
When the PCM receives two camshaft pulses fol-
lowed by the long flat spot on the camshaft sprocket,
it knows that the crankshaft timing marks for cylin-
der one are next (on driveplate). When the PCM
receives one camshaft pulse after the long flat spot
on the sprocket, cylinder number two crankshaft tim-
ing marks are next. After 3 camshaft pulses, the
PCM knows cylinder four crankshaft timing marks
follow. One camshaft pulse after the three pulses
indicates cylinder five. The two camshaft pulses after
cylinder 5 signals cylinder six (Fig. 3). The PCM can
synchronize on cylinders 1 or 4.
NSFUEL SYSTEM 14 - 33
DESCRIPTION AND OPERATION (Continued)