change time CHRYSLER VOYAGER 1996 Owner's Manual

(6) Tap the piston down in cylinder bore, using a
hammer handle. At the same time, guide connecting
rod into position on connecting rod journal.
(7) The notch or groove on top of piston must be
pointing toward front of engine (Fig. 60).
(8) Install rod caps. Install nuts on cleaned and
oiled rod bolts and tighten nuts to 54 N´m (40 ft. lb.)
Plus 1/4 turn.
(9) Repeat procedure for each piston and rod
installation.
(10) Install cylinder heads and oil pan.
(11) Fill engine crankcase with proper oil to cor-
rect level.
(12) Connect negative cable to battery.
CRANKSHAFT
MAIN BEARINGS
Bearing caps are not interchangeable and should
be marked at removal to insure correct assembly
(Fig. 62). Upper and lower bearing halves are NOT
interchangeable. Lower main bearing halves of 1, 3
and 4 are interchangeable. Upper main bearing
halves of 1, 3 and 4 are interchangeable.
CRANKSHAFT MAIN JOURNALS
The crankshaft journals should be checked for
excessive wear, taper and scoring. (Fig. 61) Limits of
taper or out-of-round on any crankshaft journals
should be held to 0.025 mm (0.001 in.). Journal
grinding should not exceed 0.305 mm (0.012 in.)
under the standard journal diameter. Do NOT grind
thrust faces of Number 2 main bearing. Do NOT nick
crank pin or bearing fillets. After grinding, remove
rough edges from crankshaft oil holes and clean out
all passages.
CAUTION: With the nodular cast iron crankshafts
used it is important that the final paper or cloth pol-ish after any journal regrind be in the same direc-
tion as normal rotation in the engine.
Upper and lower Number 2 bearing halves are
flanged to carry the crankshaft thrust loads and are
NOT interchangeable with any other bearing halves
in the engine (Fig. 63). All bearing cap bolts removed
during service procedures are to be cleaned and oiled
before installation. Bearing shells are available in
standard and the following undersizes: 0.025 mm
(0.001 in.) and 0.254 mm (0.010 in). Never install an
undersize bearing that will reduce clearance below
specifications.
REMOVAL
(1) Remove oil pan and identify bearing caps
before removal.
(2) Remove bearing caps one at a time. Remove
upper half of bearing by inserting Special Main Bear-
ing Tool C-3059. (Fig. 64) into the oil hole of crank-
shaft.
Fig. 60 Piston I.D. NotchesFig. 61 Measure Crankshaft Journal O.D.
Fig. 62 Main Bearing Cap Identification
9 - 116 3.3/3.8L ENGINENS
REMOVAL AND INSTALLATION (Continued)

on the thrust direction. Staggering ring gap is impor-
tant for oil control.
PISTON AND ROD ÐINSTALLATION
(1) Before installing pistons and connecting rod
assemblies into the bore, be sure that compression
ring gaps are staggered so that neither is in line with
oil ring rail gap.
(2) Before installing the ring compressor, make
sure the oil ring expander ends are butted and the
rail gaps located as shown in (Fig. 80).
(3) Immerse the piston head and rings in clean
engine oil, slide the ring compressor, over the piston
(Fig. 81).Be sure position of rings does not
change during this operation.
(4) The weight stamp designation L or H will be in
the front half of the piston should face toward the
front of the engine for SOHC engine. The arrow
should face toward the front of the engine for DOHC
engine (Fig. 75).
(5) Rotate crankshaft so that the connecting rod
journal is on the center of the cylinder bore. Insertrod and piston assembly into cylinder bore and guide
rod over the crankshaft journal.
(6) Tap the piston down in cylinder bore, using a
hammer handle. At the same time, guide connecting
rod into position on connecting rod journal.
(7) Install rod caps. InstallNewbolts and tighten
to 27 N´m (20 ft.lb.) Plus 1/4 turn.
VIBRATION DAMPER
NOTE: If a gap is found in the crankshaft damper,
in the area where the Poly-V Generator belt rides
this is normal and is acceptable (Fig. 82).
REMOVAL
(1) Remove accessory drive belts. Refer to Group 7,
Cooling System for procedure outlined in that sec-
tion.
(2) Remove crankshaft damper bolt. Remove
damper using the large side of Special Tool 1026 and
insert 6827±A (Fig. 83).
Fig. 80 Piston Ring End Gap Position
Fig. 81 Installing Piston
Fig. 82 Weld Gap
Fig. 83 Crankshaft DamperÐRemoval
9 - 28 ENGINENS/GS
REMOVAL AND INSTALLATION (Continued)

HYDRAULIC TAPPETS
Before disassembling any part of the engine to cor-
rect tappet noise, check the oil pressure. If vehicle
has no oil pressure gauge, install a reliable gauge at
the pressure sending unit. The pressure should be
between 3.5 bars to 5.0 bars at 4000 RPM.
Check the oil level after the engine reaches normal
operating temperature. Allow 5 minutes to stabilize
oil level, check dipstick. The oil level in the pan
should never be above the FULL mark or below the
ADD OIL mark on dipstick. Either of these 2 condi-
tions could be responsible for noisy tappets.
OIL LEVEL HIGH
If oil level is above the FULL mark, it is possible
for the connecting rods to dip into the oil. With the
engine running, this condition could create foam in
the oil pan. Foam in oil pan would be fed to the
hydraulic tappets by the oil pump causing them to
lose length and allow valves to seat noisily.
OIL LEVEL LOW
Low oil level may allow oil pump to take in air.
When air is fed to the tappets, they lose length which
allows valves to seat noisily. Any leaks on intake side
of oil pump through which air can be drawn will cre-
ate the same tappet action. Check the lubrication
system from the intake strainer to the pump cover,
including the relief valve retainer cap. When tappet
noise is due to aeration, it may be intermittent or
constant, and usually more than 1 tappet will be
noisy. When oil level and leaks have been corrected,
operate the engine at fast idle. Run engine for a suf-
ficient time to allow all of the air inside the tappets
to be bled out.
TAPPET NOISE DIAGNOSIS
(1) To determine source of tappet noise, operate
engine at idle with cylinder head covers removed.
(2) Feel each valve spring or rocker arm to detect
noisy tappet. The noisy tappet will cause the affected
spring and/or rocker arm to vibrate or feel rough in
operation.
NOTE: Worn valve guides or cocked springs are
sometimes mistaken for noisy tappets. If such is
the case, noise may be dampened by applying side
thrust on the valve spring. If noise is not apprecia-
bly reduced, it can be assumed the noise is in the
tappet. Inspect the rocker arm push rod sockets
and push rod ends for wear.
(3) Valve tappet noise ranges from light noise to a
heavy click. A light noise is usually caused by exces-
sive leak down around the unit plunger or by the
plunger partially sticking in the tappet body cylinder.
The tappet should be replaced. A heavy click iscaused by a tappet check valve not seating or by for-
eign particles becoming wedged between the plunger
and the tappet body. This will cause the plunger to
stick in the down position. This heavy click will be
accompanied by excessive clearance between the
valve stem and rocker arm as valve closes. In either
case, tappet assembly should be removed for inspec-
tion and cleaning.
(4) The valve train generates a noise very much
like a light tappet noise during normal operation.
Care must be taken to ensure that tappets are mak-
ing the noise. In general, if more than one tappet
seems to be noisy, its probably not the tappets.
SERVICE PROCEDURES
CHECKING OIL LEVEL
To assure proper engine lubrication, the engine oil
must be maintained at the correct level. Check the
oil level at regular intervals, such as every fuel stop.
The best time to check the oil level is about 5 min-
utes after a fully warmed-up engine is shut off, or
before starting the vehicle after it has sat overnight.
Checking the oil while the vehicle is on level
ground, will improve the accuracy of the oil level
readings (Fig. 4).
CHANGING ENGINE OIL AND FILTER
Change engine oil and filter at mileage and time
intervals described in the Maintenance Schedule.
Fig. 4 Checking Engine Oil
NS/GSENGINE 9 - 47
DIAGNOSIS AND TESTING (Continued)

(36) Operate the engine with the radiator cap off.
Inspect for leaks and continue operating the engine
until the thermostat opens. Add coolant, if required.
VALVES AND VALVE SPRINGSÐHEAD OFF
This procedure is done with the engine cylinder
head removed from the block.
REMOVAL
(1) Remove the engine cylinder head from the cyl-
inder block. Refer to cylinder head removal in this
section.
(2) Use Valve Spring Compressor Tool and com-
press each valve spring.
(3) Remove the valve locks, retainers, and springs.
(4) Use an Arkansas smooth stone or a jewelers
file to remove any burrs on the top of the valve stem,
especially around the groove for the locks.
(5) Remove the valves, and place them in a rack in
the same order as removed.
INSTALLATION
(1) Fit each valve to its respective valve guide.
NOTE: If valves and valve seats have been refaced
refer to Service Procedures in this section. Follow
The Valve Stand Down procedure.
(2) Install lower, washer and spring.
(3) Install upper spring collar, and compress valve
spring with spring compressor tool. Install split cone
retainers.
HYDRAULIC TAPPETS
REMOVAL
(1) Remove coolant pressure bottle.
(2) Remove cylinder head cover. Refer to cylinder
head cover removal in this section.
(3) Remove rocker assembly and push rods. Iden-
tify push rods to ensure installation in original loca-
tion (Fig. 34).
(4) Remove cylinder head, intake manifold, and
exhaust manifold. Refer to cylinder head removal in
this section.
(5) Remove yoke retainer and aligning yokes (Fig.
35).
(6) Slide Hydraulic Tappet Remover/Installer Tool
through opening in block and seat tool firmly in the
head of tappet.
(7) Pull tappet out of bore with a twisting motion.
If all tappets are to be removed, identify tappets to
ensure installation in original location.
(8) If the tappet or bore in cylinder block is scored,
scuffed, or shows signs of sticking, ream the bore to
next oversize. Replace with oversize tappet.CAUTION: The plunger and tappet bodies are not
interchangeable. The plunger and valve must
always be fitted to the original body. It is advisable
to work on one tappet at a time to avoid mixing of
parts. Mixed parts are not compatible. DO NOT dis-
assemble a tappet on a dirty work bench.
INSTALLATION
(1) Lubricate tappets.
(2) Install tappets and yoke retainers in their orig-
inal positions. Ensure that the oil feed hole in the
side of the tappet body faces up (away from the
crankshaft).
Fig. 34 Tappet and Rocker Arm Assembly
Fig. 35 Tappet and Yoke
9 - 60 ENGINENS/GS
REMOVAL AND INSTALLATION (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)

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)

The crankshaft position sensor is located in the
transaxle housing, above the vehicle speed sensor
(Fig. 10). The bottom of the sensor is positioned next
to the drive plate.The distance between the bot-
tom of sensor and the drive plate is critical to
the operation of the system. When servicing the
crankshaft position sensor, refer to the appro-
priate Multi-Port Fuel Injection Service Proce-
dures section in this Group.
2.4L
The second crankshaft counterweight has
machined into it two sets of four timing reference
notches and a 60 degree signature notch (Fig. 11).
From the crankshaft position sensor input the PCM
determines engine speed and crankshaft angle (posi-
tion).
The notches generate pulses from high to low in
the crankshaft position sensor output voltage. When
a metal portion of the counterweight aligns with the
crankshaft position sensor, the sensor output voltagegoes low (less than 0.3 volts). When a notch aligns
with the sensor, voltage spikes high (5.0 volts). As a
group of notches pass under the sensor, the output
voltage switches from low (metal) to high (notch)
then back to low.
If available, an oscilloscope can display the square
wave patterns of each voltage pulse. From the width
of the output voltage pulses, the PCM calculates
engine speed. The width of the pulses represent the
amount of time the output voltage stays high before
switching back to low. The period of time the sensor
output voltage stays high before switching back to
low is referred to as pulse width. The faster the
engine is operating, the smaller the pulse width on
the oscilloscope.
By counting the pulses and referencing the pulse
from the 60 degree signature notch, the PCM calcu-
lates crankshaft angle (position). In each group of
timing reference notches, the first notch represents
69 degrees before top dead center (BTDC). The sec-
ond notch represents 49 degrees BTDC. The third
notch represents 29 degrees. The last notch in each
set represents 9 degrees before top dead center
(TDC).
The timing reference notches are machined to a
uniform width representing 13.6 degrees of crank-
shaft rotation. From the voltage pulse width the
PCM tells the difference between the timing refer-
ence notches and the 60 degree signature notch. The
60 degree signature notch produces a longer pulse
width than the smaller timing reference notches. If
the camshaft position sensor input switches from
high to low when the 60 degree signature notch
passes under the crankshaft position sensor, the
PCM knows cylinder number one is the next cylinder
at TDC.
The crankshaft position sensor mounts to the
engine block behind the generator, just above the oil
filter (Fig. 12).
ENGINE COOLANT TEMPERATURE SENSORÐPCM
INPUT
The engine coolant temperature sensor is a vari-
able resistor with a range of -40ÉC to 129ÉC (-40ÉF to
265ÉF).
The engine coolant temperature sensor provides an
input voltage to the PCM. As coolant temperature
varies, the sensor resistance changes resulting in a
different input voltage to the PCM.
When the engine is cold, the PCM will demand
slightly richer air/fuel mixtures and higher idle
speeds until normal operating temperatures are
reached.
The engine coolant sensor is also used for cooling
fan control.
Fig. 10 Crankshaft Position Sensor LocationÐ3.0/
3.3/3.8L
Fig. 11 Timing Reference Notches
14 - 36 FUEL SYSTEMNS
DESCRIPTION AND OPERATION (Continued)

a fixed vehicle speed has been selected. The speed
control RESUME voltage indicates the previous fixed
speed is requested. The speed control CANCEL volt-
age tells the PCM to deactivate but retain set speed
in memory (same as depressing the brake pedal). The
speed control OFF voltage tells the PCM that the
speed control system has deactivated. Refer to Group
8H for more speed control information.
TRANSAXLE PARK/NEUTRAL SWITCHÐPCM
INPUT
The park/neutral switch is located on the transaxle
housing (Fig. 25). It provides an input to the PCM
indicating whether the automatic transaxle is in
Park or Neutral. This input is used to determine idlespeed (varying with gear selection) and ignition tim-
ing advance. The park neutral switch is sometimes
referred to as the neutral safety switch.
THROTTLE POSITION SENSOR (TPS)ÐPCM INPUT
The TPS is mounted on the throttle body and con-
nected to the throttle blade shaft (Fig. 26) or (Fig.
27) or (Fig. 28). The TPS is a variable resistor that
provides the (PCM) with an input signal (voltage)
representing throttle blade position. As the position
of the throttle blade changes, the resistance of the
TPS changes.
Fig. 23 MAP SensorÐ3.0L
Fig. 24 MAP SensorÐ2.4L
Fig. 25 Park Neutral SwitchÐ4-Speed Electronic
Automatic TransaxleÐTypical
Fig. 26 Throttle Position SensorÐ3.3/3.8L
14 - 40 FUEL SYSTEMNS
DESCRIPTION AND OPERATION (Continued)

(brake, park/neutral, air conditioning). Deceleration
die out is also prevented by increasing airflow when
the throttle is closed quickly after a driving (speed)
condition.
DUTY CYCLE EVAP CANISTER PURGE
SOLENOIDÐPCM OUTPUT
The duty cycle EVAP purge solenoid regulates the
rate of vapor flow from the EVAP canister to the
throttle body. The PCM operates the solenoid.
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged. The
PCM de-energizes the solenoid during open loop oper-
ation.
The engine enters closed loop operation after it
reaches a specified temperature and the time delay
ends. During closed loop operation, the PCM ener-
gizes and de-energizes the solenoid 5 or 10 times per
second, depending upon operating conditions. The
PCM varies the vapor flow rate by changing solenoid
pulse width. Pulse width is the amount of time the
solenoid energizes.
A rubber boot covers the duty cycle EVAP purge
solenoid. The solenoid attaches to a bracket mounted
to the right engine mount (Fig. 31). The top of the
solenoid has the word TOP on it. The solenoid will
not operate properly unless it is installed correctly.
PROPORTIONAL PURGE SOLENOID
All vehicles use a proportional purge solenoid. The
solenoid regulates the rate of vapor flow from theEVAP canister to the throttle body. The PCM oper-
ates the solenoid.
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged.
The proportional purge solenoid operates at a fre-
quency of 200 hz and is controlled by an engine con-
troller circuit that senses the current being applied
to the proportional purge solenoid and then adjusts
that current to achieve the desired purge flow. The
proportional purge solenoid controls the purge rate of
fuel vapors from the vapor canister and fuel tank to
the engine intake manifold.
ELECTRONIC EGR TRANSDUCER SOLENOIDÐPCM
OUTPUT
The electronic EGR transducer contains an electri-
cally operated solenoid and a back-pressure trans-
ducer (Fig. 33) or (Fig. 34) or (Fig. 35). The PCM
operates the solenoid. The PCM determines when to
energize the solenoid. Exhaust system back-pressure
controls the transducer.
When the PCM energizes the solenoid, vacuum
does not reach the transducer. Vacuum flows to the
transducer when the PCM de-energizes the solenoid.
When exhaust system back-pressure becomes high
enough, it fully closes a bleed valve in the trans-
ducer. When the PCM de-energizes the solenoid and
back-pressure closes the transducer bleed valve, vac-
uum flows through the transducer to operate the
EGR valve.
De-energizing the solenoid, but not fully closing the
transducer bleed hole (because of low back-pressure),
varies the strength of vacuum applied to the EGR
valve. Varying the strength of the vacuum changes
the amount of EGR supplied to the engine. This pro-
Fig. 31 Duty Cycle EVAP Purge Solenoid
Fig. 32 Proportional Purge Solenoid
NSFUEL SYSTEM 14 - 43
DESCRIPTION AND OPERATION (Continued)

Shutdown (ASD) RelayÐPCM Output in this section
for relay operation.
TORQUE CONVERTER CLUTCH SOLENOIDÐPCM
OUTPUT
Three-speed automatic transaxles use a torque con-
verter clutch solenoid. The PCM controls the engage-
ment of the torque converter clutch through the
solenoid. The torque converter clutch is engaged only
in direct drive mode. Refer to Group 21 for transaxle
information.
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMPÐPCM OUTPUT
The PCM supplies the malfunction indicator (check
engine) lamp on/off signal to the instrument panel
through the CCD Bus. The CCD Bus is a communi-
cations port. Various modules use the CCD Bus to
exchange information.
The Check Engine lamp comes on each time the
ignition key is turned ON and stays on for 3 seconds
as a bulb test.
The Malfunction Indicator Lamp (MIL) stays on
continuously, when the PCM has entered a Limp-In
mode or identified a failed emission component. Dur-
ing Limp-in Mode, the PCM attempts to keep the
system operational. The MIL signals the need for
immediate service. In limp-in mode, the PCM com-
pensates for the failure of certain components that
send incorrect signals. The PCM substitutes for the
incorrect signals with inputs from other sensors.
If the PCM detects active engine misfire severe
enough to cause catalyst damage, it flashes the MIL.
At the same time the PCM also sets a Diagnostic
Trouble Code (DTC).
For signals that can trigger the MIL (Check
Engine Lamp) refer to Group 25, On-Board
Dianostics.
SOLID STATE FAN RELAYÐPCM OUTPUT
The radiator fan runs at a variable speed depend-
ing on coolant temperature and A/C system pressure.
The radiator fan circuit contains a Solid State Fan
Relay (SSFR). Refer to the Group 8W for a circuit
schematic.
A 5 volt signal is supplied to the SSFR. The PCM
provides a pulsed ground for the SSFR. Depending
upon the amount of pulse on time, the SSFR puts out
a proportional voltage to the fan motor at the lower
speed. For instance, if the on time is 30 percent, then
the voltage to the fan motor will be 3.6 volts.
When engine coolant reaches approximately 102ÉC
(215ÉF) the PCM grounds the SSFR relay. If engine
coolant reaches 207ÉC (225ÉF) the PCM grounds the
high speed ground relay and high speed fan relay. If
the fan operates at high speed, the PCM de-energizes
the high speed relay and high speed ground relay
when coolant temperature drops to approximately
101ÉC (214ÉF). When coolant temperature drops to
101ÉC (214ÉF) the fan operates at low speed. The
PCM de-energizes the low speed relay when coolant
temperature drops to approximately 93ÉC (199ÉF).
Also, when the air conditioning pressure switch
closes, the fan operates at high speed. The air condi-
tioning switch closes at 285 psi610 psi. When air
conditioning pressure drops approximately 40 psi, the
pressure switch opens and the fan operates at low
speed.
The SSFR relay is located on the left front inner
frame just behind the radiator (Fig. 42).
SPEED CONTROL SOLENOIDSÐPCM OUTPUT
The speed control vacuum and vent solenoids are
operated by the PCM. When the PCM supplies a
ground to the vacuum and vent solenoids, the speed
control system opens the throttle plate. When the
PCM removes the ground from the vacuum and vent
solenoids, the throttle blade closes. The PCM bal-
Fig. 41 Ignition Coil Ð3.3/3.8L
Fig. 42 Fan Control Module
14 - 46 FUEL SYSTEMNS
DESCRIPTION AND OPERATION (Continued)