2001 DODGE TOWN AND COUNTRY Engine

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 oxygen
sensor 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 35É the PCM will wait 44
seconds.
²If the coolant is over 50ÉF the PCM will wait 38
seconds.
²If the coolant is over 167ÉF the PCM will wait
11 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 0.1 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
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 and heated oxygen sen-
sors.
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 within664 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:
²Battery voltage
²Engine coolant temperature
²Engine RPM
²Inlet/Intake air temperature (IAT)
²MAP
²Throttle position
RSFUEL INJECTION14-17
FUEL INJECTION (Continued)
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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:
²Engine coolant temperature
²Manifold Absolute Pressure (MAP)
²Inlet/Intake air temperature (IAT)
²Crankshaft position (engine speed)
²Camshaft position
²Knock 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:
²Inlet/Intake air temperature
²Engine coolant temperature
²Manifold absolute pressure
²Crankshaft position (engine speed)
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.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
²Purge system monitor
²All inputs monitored for proper voltage range.
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.
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
²Engine coolant temperature
²Engine run time
²Inlet/Intake air temperature
²Vehicle mileageACCELERATION 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.
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
²IAC motor 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. In response, the PCM may
14 - 18 FUEL INJECTIONRS
FUEL INJECTION (Continued)
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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.
The PCM does not monitor the heated oxygen sen-
sor inputs during wide-open-throttle operation except
for downstream heated oxygen sensor and both
shorted diagnostics. The PCM adjusts injector pulse
width to supply a predetermined amount of addi-
tional fuel.
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.
Long Term
The second fuel correction program is the long
term adaptive memory. In order to maintain correct
emission throughout all operating ranges of the
engine, a cell structure based on engine rpm and load
(MAP) is used.
Ther number of cells varies upon the driving con-
ditions. Two cells are used only during idle, based
upon TPS and Park/Neutral switch inputs. There
may be two other cells used for deceleration, based
on TPS, engine rpm, and vehicle speed. The other
twelve cells represent a manifold pressure and an
rpm range. Six of the cells are high rpm and the
other six are low rpm. Each of these cells is a specific
MAP voltage range .
As the engine enters one of these cells the PCM
looks at the amount of short term correction being
used. Because the goal is to keep short term at 0 (O2
Sensor switching at 0.5 volt), long term will update
in the same direction as short term correction was
moving to bring the short term back to 0. Once short
term is back at 0, this long term correction factor is
stored in memory.
The values stored in long term adaptive memory
are used for all operating conditions, including open
loop. However, the updating of the long term memory
occurs after the engine has exceeded approximately
17É F, with fuel control in closed loop and two min-
utes of engine run time. This is done to prevent any
transitional temperature or start-up compensations
from corrupting long term fuel correction.
Long term adaptive memory can change the pulse-
width by as much as 25%, which means it can correct
for all of short term. It is possible to have a problem
that would drive long term to 25% and short term to
another 25% for a total change of 50% away from
base pulse-width calculation.
RSFUEL INJECTION14-19
FUEL INJECTION (Continued)
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TYPICAL ADAPTIVE MEMORY FUEL CELLS
Open
ThrottleOpen
ThrottleOpen
ThrottleOpen
ThrottleOpen
ThrottleOpen
Throttle Idle Decel
Vacuum 20 17 13 9 5 0
Above 1,984
rpm1 3 5 7 9 11 13 Drive 15
Below 1,984
rpm02 4 6 8 1012
Neutral14
MAP volt =0 1.4 2.0 2.6 3.3 3.9
Fuel Correction Diagnostics
There are two fuel correction diagnostic routines:
²Fuel System Rich
²Fuel System Lean
A DTC is set and the MIL is illuminated if the
PCM detects either of these conditions.
PROGRAMMABLE COMMUNICATIONS
INTERFACE (PCI) BUS
DESCRIPTION
The Programmable Communication Interface Mul-
tiplex system (PCI Bus) consist of a single wire. The
Body Control Module (BCM) acts as a splice to con-
nect each module and the Data Link Connector
(DLC) together. Each module is wired in parallel to
the data bus through its PCI chip set and uses its
ground as the bus reference. The wiring is a mini-
mum 20 gage wire.
OPERATION
Various modules exchange information through a
communications port called the PCI Bus. The Power-
train Control Module (PCM) transmits the Malfunc-
tion Indicator Lamp (Check Engine) On/Off signaland engine RPM on the PCI Bus. The PCM receives
the Air Conditioning select input, transaxle gear
position inputs over the PCI Bus. The PCM also
receives the air conditioning evaporator temperature
signal from the PCI Bus.
The following components access or send informa-
tion on the PCI Bus.
²Instrument Panel
²Body Control Module
²Air Bag System Diagnostic Module
²Full ATC Display Head
²ABS Module
²Transmission Control Module
²Powertrain Control Module
²Overhead Travel Module
SYSTEM DIAGNOSIS
OPERATION
The PCM can test many of its own input and out-
put circuits. If the PCM senses a fault in a major
system, the PCM stores a Diagnostic Trouble Code
(DTC) in memory.
For DTC information see On-Board Diagnostics.
14 - 20 FUEL INJECTIONRS
FUEL INJECTION (Continued)
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ACCELERATOR PEDAL
REMOVAL
(1) Hold the throttle body throttle lever in the
wide open position. Remove the throttle cable from
the throttle body cam.
(2) From inside the vehicle, hold up the pedal and
remove the cable retainer and throttle cable from the
upper end of the pedal shaft.
(3) Remove nuts from accelerator pedal attaching
studs. Remove assembly from vehicle.
INSTALLATION
(1) Position accelerator pedal assembly on dash
panel. Install retaining nuts. Tighten retaining nuts
to 12 N´m (105 in. lbs.) torque.
(2) From inside the vehicle, hold up the pedal and
install the throttle cable and cable retainer in the
upper end of the pedal shaft.
(3) From the engine compartment, hold the throt-
tle body lever in the wide open position and install
the throttle cable.
CRANKSHAFT POSITION
SENSOR
DESCRIPTION
The 2.4L crankshaft sensor is located on the rear
of the engine near the accessory drive belt (Fig. 1).
The 3.3/3.8L crankshaft sensor is located on the rear
of the transmission housing, above the differential
housing (Fig. 2). The bottom of the sensor is posi-
tioned next to the drive plate.
OPERATION
The crankshaft position sensor detects slots cut
into the transmission driveplate extension (Fig. 3).
There are 3 sets of slots. Each set contains 4 slots,
for a total of 12 slots (Fig. 4). Basic timing is set by
the position of the last slot in each group. Once the
Powertrain Control Module (PCM) senses the last
slot, it determines crankshaft position (which piston
will next be at TDC) from the camshaft position sen-
sor input. The 4 pulses generated by the crankshaft
position sensor represent the 69É, 49É, 29É, and 9É
BTDC marks. It may take the PCM one engine rev-
olution to determine crankshaft position.
The PCM uses crankshaft position reference to
determine injector sequence, ignition timing and the
presence of misfire. Once the PCM determines crank-
shaft position, it begins energizing the injectors in
sequence.
REMOVAL
(1) Disconnect the negative battery cable.
(2) Raise vehicle and support.
(3) Disconnect the electrical connector (Fig. 5).
(4) Remove crankshaft sensor bolt.
(5) Remove the crankshaft sensor.
REMOVAL - 3.3/3.8L
(1) Remove battery, refer to the Battery section for
more information.
(2) Remove the battery tray, refer to the Battery
section for more information.
Fig. 1 CRANKSHAFT SENSOR 2.4L
1 - CRANKSHAFT POSITION SENSOR
Fig. 2 CRANKSHAFT SENSOR 3.3/3.8L
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(3) Disconnect the speed control vacuum harness
from servo.
(4) Remove the speed control servo and bracket
and reposition. Disconnect the electrical connector.
(5) Disconnect the electrical connector from crank-
shaft sensor.
(6) Remove the mounting bolt.
(7) Remove sensor.
INSTALLATION - 2.4L
(1) Install the crankshaft sensor.
(2) Install crankshaft sensor bolt and tighten.
(3) Connect the electrical connector (Fig. 5).
(4) Lower vehicle.
(5) Connect the negative battery cable.
INSTALLATION - 3.3/3.8L
(1) Install the crankshaft sensor.
(2) Install the mounting bolt and tighten.
(3) Connect the electrical connector to crankshaft
sensor. Make sure locking tab is in position.
(4) Connect the electrical connector to the speed
control servo.
(5) Install the speed control servo and bracket.
(6) Connect the speed control vacuum harness to
servo.
(7) Install the battery tray, refer to the Battery
section for more information.
(8) Install battery, refer to the Battery section for
more information.
ENGINE SPEED SENSOR
DESCRIPTION
The PCM receives a signal from the TCM and the
transaxle output speed sensor over the bus communi-
cation line.
OPERATION
The Transmission Control Module (TCM) supplies
the road speed and distance traveled inputs to the
PCM. From these inputs and the throttle position
sensor input, the PCM determines when a decelera-
tion condition occurs.
Fig. 3 Crankshaft Position Sensor
1 - CRANKSHAFT POSITION SENSOR
Fig. 4 Timing Slots
1 - TORQUE CONVERTER DRIVE PLATE
2 - SLOTS
Fig. 5 CRANKSHAFT SENSOR 2.4L
1 - CRANKSHAFT POSITION SENSOR
14 - 24 FUEL INJECTIONRS
CRANKSHAFT POSITION SENSOR (Continued)
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FUEL INJECTOR
DESCRIPTION
The injectors are positioned in the intake manifold
with the nozzle ends directly above the intake valve
port (Fig. 6).
OPERATION
The fuel injectors are electrical solenoids (Fig. 7).
The injector contains a pintle that closes off an ori-
fice at the nozzle end. When electric current is sup-
plied to the injector, the armature and needle move a
short distance against a spring, allowing fuel to flow
out the orifice. Because the fuel is under high pres-
sure, a fine spray is developed in the shape of a hol-
low cone or two streams. The spraying action
atomizes the fuel, adding it to the air entering the
combustion chamber. Fuel injectors are not inter-
changeable between engines.
The PCM provides battery voltage to each injector
through the ASD relay. Injector operation is con-
trolled by a ground path provided for each injector by
the PCM. Injector on-time (pulse-width) is variable,
and is determined by the PCM processing all the
data previously discussed to obtain the optimum
injector pulse width for each operating condition. The
pulse width is controlled by the duration of the
ground path provided.
Fuel injectors are fired one crankshaft revolution
before TDC compression. When cylinder #4 is at TDC
compression the injector for cylinder #1 will be ener-
gized.
REMOVAL - 2.4L
The fuel rail must be removed first (Fig. 8). Refer
to Fuel Rail Removal in this section.
Fig. 6 Fuel Injector Location Typical
1 - FUEL RAIL
2 - INTAKE MANIFOLD
3 - FUEL INJECTORS
Fig. 7 FUEL INJECTOR TYPICAL
1 - FUEL INJECTOR
2 - NOZZLE
3 - TOP (FUEL ENTRY)
Fig. 8 FUEL RAIL AND INJECTORS 2.4L
1 - Fuel Injectors
2 - Fuel Rail
RSFUEL INJECTION14-25
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(1) Disconnect injector wiring connector from injec-
tor.
(2) Position fuel rail assembly so that the fuel
injectors are easily accessible (Fig. 9).
(3) Rotate injector and pull injector out of fuel rail.
The clip will stay on the injector.
(4) Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is reused, a
protective cap must be installed on the injector tip to
prevent damage. Replace the injector clip if it is dam-
aged.
(5) Repeat for remaining injectors.
REMOVAL - 3.3/3.8L
(1) Disconnect the negative battery cable.
(2) Remove the Intake Manifold, (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
REMOVAL)
(3) Disconnect injector wiring connector from injec-
tor.
(4) Position fuel rail assembly so that the fuel
injectors are easily accessible (Fig. 9).
(5) Rotate injector and pull injector out of fuel rail.
The clip will stay on the injector.
(6)
Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is reused, a
protective cap must be installed on the injector tip to
prevent damage. Replace the injector clip if it is dam-
aged.
(7) Repeat for remaining injectors.
INSTALLATION - 2.4L
The fuel rail must be removed first. Refer to Fuel
Injector Rail Removal in this section.
(1) Before installing an injector the rubber O-ring
must be lubricated with a drop of clean engine oil to
aid in installation.
(2) Install injector clip by sliding open end into the
top slot of the injector. The edge of the receiver cup
will slide into the side slots of clip.
(3) Install injector top end into fuel rail receiver
cap. Be careful not to damage O-ring during installa-
tion (Fig. 10).
(4) Repeat steps for remaining injectors.
(5) Connect fuel injector wiring.
INSTALLATION - 3.3/3.8L
(1) Before installing an injector the rubber O-ring
must be lubricated with a drop of clean engine oil to
aid in installation.
(2) Install injector clip by sliding open end into the
top slot of the injector. The edge of the receiver cup
will slide into the side slots of clip (Fig. 9).
(3) Install injector top end into fuel rail receiver
cap. Be careful not to damage O-ring during installa-
tion (Fig. 9).
(4) Repeat steps for remaining injectors.
(5) Install fuel rail, refer to Fuel Rail in the Fuel
Delivery section.
(6) Connect fuel injector wiring.
(7) Install the Intake Manifold, (Refer to 9 -
ENGINE/MANIFOLDS/INTAKE MANIFOLD -
INSTALLATION)
(8) Connect the negative battery cable.
Fig. 9 FUEL INJECTOR AND RAIL TYPICAL
1 - FUEL RAIL ASSEMBLY
2 - FUEL INJECTOR
3 - FUEL RAIL RECEIVER
Fig. 10 SERVICING FUEL INJECTOR TYPICAL
1 - FUEL INJECTOR
2 - LOCKING SLOT
3 - FUEL RAIL RECEIVER CUP
14 - 26 FUEL INJECTIONRS
FUEL INJECTOR (Continued)
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