2002 CHRYSLER CARAVAN coolant temperature

(5) Slide exhaust manifold and turbocharger on
exhaust manifold studs (Fig. 17).
(6) Install exhaust manifold retaining nuts. Torque
nuts to 32.4N´m.
(7) Install exhaust manifold heat shield (Fig. 17).
Torque bolts to 27.5N´m.
(8) Install turbocharger outlet to charge air cooler
pipe (Fig. 16).
(9) Install thermostat housing to upper radiator
hose pipe (Fig. 16). Install retaining bolt and torque
to 47.1N´m.
(10) Install coolant recovery pressure container
(Refer to 7 - COOLING/ENGINE/COOLANT RECOV-
ERY PRESS CONTAINER - INSTALLATION).
(11) Connect glow plug and coolant temperature
sensor electrical connectors.
(12) Install new cylinder head cover/intake mani-
fold gasket.
(13) Install rocker arm and lifter assemblies.Be
sure to put rocker arm and lifter assemblies in
same location as removed.
(14) Install cylinder head cover/intake manifold
(Fig. 15)(Refer to 9 - ENGINE/CYLINDER HEAD/
CYLINDER HEAD COVER(S) - INSTALLATION).
(15) Install timing belt inner cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION).
(16) Install timing belt (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - INSTALLATION) .
(17) Install timing belt outer cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION).
(18)Remove crankshaft and both camshaft
locking pins at this time(Refer to 9 - ENGINE/
VALVE TIMING - STANDARD PROCEDURE).
(19) Install generator (Refer to 8 - ELECTRICAL/
CHARGING/GENERATOR - INSTALLATION).
(20) Install accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(21) Install power steering belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(22) Install right engine mount (Refer to 9 -
ENGINE/ENGINE MOUNTING/RIGHT MOUNT -
INSTALLATION).
(23) Install air cleaner housing assembly.
(24) Refill cooling system (Refer to 7 - COOLING/
ENGINE/COOLANT - STANDARD PROCEDURE).
(25) Install engine cover (Refer to 9 - ENGINE -
INSTALLATION).
(26) Install front wiper unit (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
INSTALLATION).
(27) Connect negative battery cable.CAMSHAFT(S)
DESCRIPTION
The camshafts are made of gray cast iron with
eight machined lobes and four bearing journals (Fig.
20).
OPERATION
When the camshaft rotates the lobes actuate the
hydraulic lifters and rocker arms, forcing downward
on the rocker arms which opens the valves.
REMOVAL
(1) Disconnect negative battery cable.
(2) Remove front wiper unit (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
REMOVAL).
(3) Remove engine cover (Refer to 9 - ENGINE -
REMOVAL).
(4) Drain cooling system (Refer to 7 - COOLING/
ENGINE/COOLANT - STANDARD PROCEDURE).
(5) Remove air cleaner housing.
(6) Remove power steering belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(7) Remove accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(8) Remove generator (Refer to 8 - ELECTRICAL/
CHARGING/GENERATOR - REMOVAL).
(9) Support engine and remove right engine mount
(Refer to 9 - ENGINE/ENGINE MOUNTING/RIGHT
MOUNT - REMOVAL).
Fig. 20 CAMSHAFTS
1 - INTAKE CAMSHAFT
2 - EXHAUST CAMSHAFT
9a - 22 ENGINERG
CYLINDER HEAD (Continued)
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CYLINDER HEAD COVER(S)
DESCRIPTION
The cylinder head cover is made of cast aluminum
and is also the intake manifold on this engine (Fig.
22).
REMOVAL
CAUTION: Before removing the cylinder head cover/
intake manifold the engine must put at 90É after
TDC. Failure to do so could result in valve and/or
piston damage during reassembly. (Refer to 9 -
ENGINE/VALVE TIMING - STANDARD PROCEDURE)
(1) Disconnect negative battery cable.
(2) Remove front wiper unit (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
REMOVAL).
(3) Remove engine cover (Refer to 9 - ENGINE -
REMOVAL).
(4) Drain cooling system (Refer to 7 - COOLING/
ENGINE/COOLANT - STANDARD PROCEDURE).
(5) Rotate engine until 90É after TDC is reached.
Install both camshaft locking pins and the crankshaft
locking pin. (Refer to 9 - ENGINE/VALVE TIMING -
STANDARD PROCEDURE)
(6) Remove air cleaner housing assembly.
(7) Remove power steering belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).(8) Remove accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(9) Remove generator (Refer to 8 - ELECTRICAL/
CHARGING/GENERATOR - REMOVAL).
(10) Support engine and remove right engine
mount (Refer to 9 - ENGINE/ENGINE MOUNTING/
RIGHT MOUNT - REMOVAL).
(11) Remove outer timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
(12) Remove timing belt (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - REMOVAL).
(13) Remove inner timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
(14) Disconnect camshaft position sensor, boost
pressure/intake air temperature sensor, EGR sole-
noid, and fuel pressure sensor electrical connectors
(Fig. 23).
Fig. 22 CYLINDER HEAD COVER/INTAKE
MANIFOLD
Fig. 23 ENGINE COMPONENT LOCATIONS
1 - FUEL INJECTOR RETURN LINE
2 - FUEL INJECTOR SUPPLY LINE
3 - OIL SEPARATOR
4 - FUEL INJECTOR
5 - CAMSHAFT POSITION SENSOR
6 - BOOST PRESSURE/INTAKE AIR TEMPERATURE SENSOR
7 - EGR SOLENOID
8 - FUEL PRESSURE SENSOR
9 - CYLINDER HEAD COVER/INTAKE MANIFOL
10 - FUEL RAIL
11 - WIRING HARNESS RETAINING CLIPS
9a - 24 ENGINERG
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(2) Remove front wiper unit (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
REMOVAL).
(3) Remove air cleaner housing assembly.
(4) Support engine and remove right engine mount
(Refer to 9 - ENGINE/ENGINE MOUNTING/RIGHT
MOUNT - REMOVAL).
(5) Remove outer timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
(6) Remove timing belt (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - REMOVAL).
(7) Remove inner timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
(8) Remove cylinder head cover/intake manifold
(Refer to 9 - ENGINE/CYLINDER HEAD/CYLIN-
DER HEAD COVER(S) - REMOVAL).(9) Remove rocker arm from lifter (Fig. 30).
INSTALLATION
(1) Clean and inspect gasket sealing surfaces.
(2) Install new gasket on cylinder head.
(3) Lubricate lifter ball end of lifter(s), valve(s),
and rocker arm roller(s) with MopartEngine Oil
Supplement or equivlalent.
(4) Connect rocker arm(s) to lifter and reposition
on valve(s) (Fig. 30).
(5) Install cylinder head cover/intake manifold
(Refer to 9 - ENGINE/CYLINDER HEAD/CYLIN-
DER HEAD COVER(S) - INSTALLATION).
(6) Install inner timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION).
(7) Install timing belt (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - INSTALLATION) .
(8) Install outer timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION).
(9) Install right engine mount (Refer to 9 -
ENGINE/ENGINE MOUNTING/RIGHT MOUNT -
INSTALLATION).
(10) Install air cleaner housing assembly.
Fig. 29 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. 30 ROCKER ARM ASSEMBLY
1 - ROCKER ARM ASSEMBLY
2 - CYLINDER HEAD COVER/INTAKE MANIFOLD
3 - HYDRAULIC LIFTER
4 - CYLINDER HEAD
5 - VALVE
9a - 28 ENGINERG
ROCKER ARMS (Continued)
ProCarManuals.com

(11) Install front wiper unit (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
INSTALLATION).
(12) Connect negative battery cable.
HYDRAULIC LIFTERS
DESCRIPTION
Valve lash is controlled by hydraulic tappets
located inside the cylinder head, in tappet bores
below the camshafts (Fig. 31).
REMOVAL
(1) Disconnect negative battery cable.
(2) Remove front wiper unit (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER MODULE -
REMOVAL).(3) Remove engine cover (Refer to 9 - ENGINE -
REMOVAL).
(4) Support engine and remove right engine mount
(Refer to 9 - ENGINE/ENGINE MOUNTING/RIGHT
MOUNT - REMOVAL).
(5) Remove outer timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
CAUTION: Before removing the cylinder head cover/
intake manifold or the timing belt the engine must
put at 90É after TDC. Failure to do so could result in
valve and/or piston damage during reassembly.
(Refer to 9 - ENGINE/VALVE TIMING - STANDARD
PROCEDURE)
(6) Remove timing belt (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - REMOVAL).
(7) Remove inner timing belt cover (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL).
(8) Remove cylinder head cover/intake manifold
(Fig. 32)(Refer to 9 - ENGINE/CYLINDER HEAD/
CYLINDER HEAD COVER(S) - REMOVAL).
Fig. 31 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. 32 CYLINDER HEAD COVER/INTAKE
MANIFOLD
1 - CYLINDER HEAD COVER/INTAKE MANIFOLD BOLTS(LONG)
2 - CYLINDER HEAD COVER/INTAKE MANIFOLD
3 - CYLINDER HEAD
4 - CYLINDER HEAD COVER/INTAKE MANIFOLD GASKET
5 - CYLINDER HEAD COVER/INTAKE MANIFOLD
BOLTS(SHORT)
RGENGINE9a-29
ROCKER ARMS (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
ProCarManuals.com

1 second. Therefore, battery voltage is not supplied to
the fuel pump, ignition coil, fuel injectors and heated
oxygen sensors.
ENGINE START-UP MODE
This is an OPEN LOOP mode. If the vehicle is in
park or neutral (automatic transaxles) or the clutch
pedal is depressed (manual transaxles) the ignition
switch energizes the starter relay. The following
actions occur when the starter motor is engaged.
²If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the Auto Shutdown (ASD) relay and fuel pump relay.
If the PCM does not receive both signals within
approximately one second, it will not energize the
ASD relay and fuel pump relay. The ASD and fuel
pump relays supply battery voltage to the fuel pump,
fuel injectors, ignition coil, (EGR solenoid and PCV
heater if equipped) and heated oxygen sensors.
²The PCM energizes the injectors (on the 69É
degree falling edge) for a calculated pulse width until
it determines crankshaft position from the camshaft
position sensor and crankshaft position sensor sig-
nals. The PCM determines crankshaft position within
1 engine revolution.
²After determining crankshaft position, the PCM
begins energizing the injectors in sequence. It adjusts
injector pulse width and controls injector synchroni-
zation by turning the individual ground paths to the
injectors On and Off.
²When the engine idles within  64 RPM of its
target RPM, the PCM compares current MAP sensor
value with the atmospheric pressure value received
during the Ignition Switch On (zero RPM) mode.
Once the ASD and fuel pump relays have been
energized, the PCM determines injector pulse width
based on the following:
²MAP
²Engine RPM
²Battery voltage
²Engine coolant temperature
²Inlet/Intake air temperature (IAT)
²Throttle position
²The number of engine revolutions since cranking
was initiated
During Start-up the PCM maintains ignition tim-
ing at 9É BTDC.
ENGINE WARM-UP MODE
This is an OPEN LOOP mode. The following inputs
are received by the PCM:
²Manifold Absolute Pressure (MAP)
²Crankshaft position (engine speed)
²Engine coolant temperature
²Inlet/Intake air temperature (IAT)
²Camshaft position²Knock sensor
²Throttle position
²A/C switch
²Battery voltage
²Vehicle speed
²Speed control
²O2 sensors
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
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising or idle
the following inputs are received by the PCM:
²Manifold absolute pressure
²Crankshaft position (engine speed)
²Inlet/Intake air temperature
²Engine coolant temperature
²Camshaft position
²Knock sensor
²Throttle position
²Exhaust gas oxygen content
²A/C control positions
²Battery voltage
²Vehicle speed
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 (measured
by the upstream and downstream heated oxygen sen-
sor).
The PCM monitors for engine misfire. During
active misfire and depending on the severity, the
PCM either continuously illuminates or flashes the
malfunction indicator lamp (Check Engine light on
instrument panel). Also, the PCM stores an engine
misfire DTC in memory, if 2nd trip with fault.
The PCM performs several diagnostic routines.
They include:
²Oxygen sensor monitor
²Downstream heated oxygen sensor diagnostics
during open loop operation (except for shorted)
²Fuel system monitor
²EGR monitor (if equipped)
²Purge system monitor
²Catalyst efficiency monitor
²All inputs monitored for proper voltage range,
rationality.
²All monitored components (refer to the Emission
section for On-Board Diagnostics).
14 - 18 FUEL INJECTIONRS
FUEL INJECTION (Continued)
ProCarManuals.com

The PCM compares the upstream and downstream
heated oxygen sensor inputs to measure catalytic con-
vertor 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 sense
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 sense
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 sensor²Manifold 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
opposite preset limit or switch point. The process
then repeats itself in the opposite direction.
Short term fuel correction will keep increasing or
decreasing injector pulse-width based upon the
upstream O2 Sensor input. The maximum range of
authority for short term memory is 25% (+/-) of base
pulse-width. Short term is violated and is lost when
ignition is turned OFF.
RSFUEL INJECTION14-19
FUEL INJECTION (Continued)
ProCarManuals.com

FUEL PUMP RELAY
DESCRIPTION
The fuel pump relay is located in the PDC. The
inside top of the PDC cover has a label showing relay
and fuse location.
OPERATION
The fuel pump relay supplies battery voltage to the
fuel pump. A buss bar in the Power Distribution Cen-
ter (PDC) supplies voltage to the solenoid side and
contact side of the relay. The fuel pump relay power
circuit contains a fuse between the buss bar in the
PDC and the relay. The fuse is located in the PDC.
Refer to the Wiring Diagrams for circuit information.
The PCM controls the fuel pump relay by switch-
ing the ground path for the solenoid side of the relay
on and off. The PCM turns the ground path off when
the ignition switch is in the Off position. When the
ignition switch is in the On position, the PCM ener-
gizes the fuel pump. If the crankshaft position sensor
does not detect engine rotation, the PCM de-ener-
gizes the relay after approximately one second.
IDLE AIR CONTROL MOTOR
DESCRIPTION
The idle air control motor is mounted on the throt-
tle body. The PCM operates the idle air control motor
(Fig. 14) or (Fig. 15).
OPERATION
The PCM adjusts engine idle speed through the
idle air control motor to compensate for engine load,
coolant temperature or barometric pressure changes.
The throttle body has an air bypass passage that
provides air for the engine during closed throttle idle.
The idle air control motor pintle protrudes into the
air bypass passage and regulates air flow through it.
The PCM adjusts engine idle speed by moving the
IAC motor pintle in and out of the bypass passage. The
adjustments are based on inputs the PCM receives.
The inputs are from the throttle position sensor, crank-
shaft position sensor, coolant temperature sensor, MAP
sensor, vehicle speed sensor and various switch opera-
tions (brake, park/neutral, air conditioning).
When engine rpm is above idle speed, the IAC is
used for the following functions:
²Off-idle dashpot
²Deceleration air flow control
²A/C compressor load control (also opens the pas-
sage slightly before the compressor is engaged so
that the engine rpm does not dip down when the
compressor engages)
Target Idle
Target idle is determined by the following inputs:
²Gear position
²ECT Sensor
²Battery voltage
²Ambient/Battery Temperature Sensor
²VSS
²TPS
²MAP Sensor
Fig. 14 TPS/IAC 2.4L
1 - Idle Air Control Motor
2 - Throttle Position Sensor
Fig. 15 TPS/IAC 3.3/3.8L
1 - Idle Air Control Motor
2 - Throttle Position Sensor
RSFUEL INJECTION14-27
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