2002 JEEP LIBERTY wire

OPERATION
The fuel pressure regulator is a mechanical device
that is not controlled by engine vacuum or the Pow-
ertrain Control Module (PCM).
The regulator is calibrated to maintain fuel system
operating pressure of approximately 339 kPa +/- 34
kPa (49.2 psi +/- 5 psi) at the fuel injectors. It con-
tains a diaphragm, calibrated springs and a fuel
return valve.
The main fuel filteris not combinedwithin the
fuel pressure regulator as in other Jeeptmodels.
Three different fuel filters are used: 1. a serviceable,
separate, externally mounted, main fuel filter; 2. a
non-serviceable primary filter located on the bottom
of the electric fuel pump; 3. a non-serviceable second-
ary filter attached to the side of the fuel pump mod-
ule.
Fuel Flow:Fuel migrates into the fuel pump mod-
ule reservoir through a one-way check valve located
on the bottom of the module. This check valve pre-
vents the reservoir from running empty such as
when going up or down hills with a low amount of
fuel in the tank. A primary fuel filter (sock) is located
at the bottom of the electric fuel pump. Fuel is drawn
in through this filter, and up to the electric fuel
pump. High pressure fuel (unregulated) is supplied
from the electric fuel pump through a high-pressure
line to one of 3 fittings on the main fuel filter. If fuel
pressure at the pressure regulator exceeds approxi-
mately 49 psi, an internal diaphragm within the reg-
ulator closes, and excess fuel is routed through a
second fitting on the main fuel filter, and back into
the fuel tank (the fuel pressure regulator is installed
into the return side of the system). Pressure regu-
lated fuel is then delivered from the third fitting on
the fuel filter, up to and through the fuel rail, and on
to the fuel injectors.
A secondary fuel filter is attached to the side of the
fuel pump module. High-pressure from the electric
fuel pump causes a siphoning action across a passage
connected to this filter, and fuel is drawn into the
fuel pump module reservoir. This is used to help keep
the module reservoir full of fuel.
The fuel pressure regulator also acts as a check
valve to maintain some fuel pressure when the
engine is not operating. This will help to start the
engine. A second check valve is located at the outlet
of the fuel pump module housing.Refer to Fuel
Pump - Description and Operation for more
information. Also refer to the Fuel Pressure
Leak Down Test, and the Fuel Pump Pressure
Tests.
A separate fuel return line from the engine is not
used with this system.
REMOVAL
The fuel pressure regulator is located in the fuel
tank. It is attached to the bottom of the upper sec-
tion of the fuel pump module with a quick-connect
fitting (Fig. 19). The fuel pump module is supplied in
2 sections (upper and lower). To replace the pressure
regulator, the bottom section of the fuel pump mod-
ule must be replaced.
(1) Remove upper and lower sections of fuel pump
module from fuel tank. Refer to Fuel Pump Module
Removal/Installation.
(2) Replace lower section of fuel pump module
(includes fuel pressure regulator).
INSTALLATION
The fuel pressure regulator is located in the fuel
tank. It is attached to the bottom of the upper sec-
tion of the fuel pump module with a quick-connect
fitting. The fuel pump module is supplied in 2 sec-
tions (upper and lower). To replace the pressure reg-
ulator, the bottom section of the fuel pump module
must be replaced.
(1) Replace lower section of fuel pump module
(includes fuel pressure regulator).
(2) Install upper and lower sections of fuel pump
module to fuel tank. Refer to Fuel Pump Module
Installation.
Fig. 19 FUEL PRESSURE REGULATOR/SENDING
UNIT ELECTRICAL CONNECTOR
1 - UPPER SECTION OF PUMP MODULE
2 - QUICK-CONNECT FITTINGS
3 - FUEL PRESSURE REGULATOR
4 - 4-WIRE ELECTRICAL CONNECTOR
5 - FUEL TANK CHECK (CONTROL) VALVE
14 - 14 FUEL DELIVERYKJ
FUEL PRESSURE REGULATOR (Continued)

Fig. 27 FUEL PRESSURE REGULATOR/SENDING
UNIT ELECTRICAL CONNECTOR
1 - UPPER SECTION OF PUMP MODULE
2 - QUICK-CONNECT FITTINGS
3 - FUEL PRESSURE REGULATOR
4 - 4-WIRE ELECTRICAL CONNECTOR
5 - FUEL TANK CHECK (CONTROL) VALVE
Fig. 28 UPPER SECTION - FUEL PUMP MODULE
1 - UPPER SECTION - FUEL PUMP MODULE
2 - FUEL TANK CHECK (CONTROL) VALVE
Fig. 29 LOWER SECTION - FUEL PUMP MODULE
1 - LOWER SECTION - FUEL PUMP MODULE
2 - RELEASE LOCK AND TAB
3 - TENSION SPRINGS
Fig. 30 FUEL PUMP MODULE GUIDES (IN FUEL
TANK)
1 - FUEL TANK (INSIDE/LOWER)
2 - FUEL PUMP MODULE GUIDES
14 - 20 FUEL DELIVERYKJ
FUEL PUMP MODULE (Continued)

FUEL INJECTION
TABLE OF CONTENTS
page page
FUEL INJECTION
DESCRIPTION.........................29
ACCELERATOR PEDAL
REMOVAL.............................29
INSTALLATION.........................30
CRANKSHAFT POSITION SENSOR
DESCRIPTION.........................30
OPERATION...........................31
REMOVAL.............................31
INSTALLATION.........................32
FUEL INJECTOR
DESCRIPTION.........................33
OPERATION
OPERATION - FUEL INJECTOR..........33
OPERATION - PCM OUTPUT............33
DIAGNOSIS AND TESTING - FUEL INJECTOR . 33
REMOVAL.............................34
INSTALLATION.........................34
FUEL PUMP RELAY
DESCRIPTION.........................34
OPERATION...........................34
DIAGNOSIS AND TESTING - FUEL PUMP
RELAY..............................34
REMOVAL.............................34
INSTALLATION.........................34
IDLE AIR CONTROL MOTOR
DESCRIPTION.........................35
OPERATION...........................35
REMOVAL.............................36INSTALLATION.........................36
INTAKE AIR TEMPERATURE SENSOR
DESCRIPTION.........................36
OPERATION...........................36
REMOVAL.............................37
INSTALLATION.........................38
MAP SENSOR
DESCRIPTION.........................38
OPERATION...........................38
REMOVAL.............................39
INSTALLATION.........................40
OXYGEN SENSOR
DESCRIPTION.........................40
OPERATION...........................40
REMOVAL.............................41
INSTALLATION.........................43
THROTTLE BODY
DESCRIPTION.........................43
OPERATION...........................43
REMOVAL.............................43
INSTALLATION.........................44
THROTTLE CONTROL CABLE
REMOVAL.............................45
INSTALLATION.........................46
THROTTLE POSITION SENSOR
DESCRIPTION.........................47
OPERATION...........................47
REMOVAL.............................47
INSTALLATION.........................48
FUEL INJECTION
DESCRIPTION
The Powertrain Control Module (PCM) operates
the fuel injection system. Refer to Powertrain Control
Module in Electronic Control Modules for informa-
tion.
ACCELERATOR PEDAL
REMOVAL
The accelerator pedal is serviced as a complete
assembly including the bracket.The accelerator pedal is connected to the upper
part of the accelerator pedal arm by a plastic
retainer (clip) (Fig. 1). This plastic retainer snaps
into the top of the accelerator pedal arm.
(1) From inside the vehicle, hold up accelerator
pedal. Remove plastic cable retainer (clip) and throt-
tle cable core wire from upper end of accelerator
pedal arm (Fig. 1). Plastic cable retainer (clip) snaps
into pedal arm.
(2) Remove 2 accelerator pedal mounting bracket
nuts. Remove accelerator pedal assembly.
KJFUEL INJECTION 14 - 29

FUEL INJECTOR
DESCRIPTION
An individual fuel injector (Fig. 9) is used for each
individual cylinder.
OPERATION
OPERATION - FUEL INJECTOR
The top (fuel entry) end of the injector (Fig. 9) is
attached into an opening on the fuel rail.
The fuel injectors are electrical solenoids. The
injector contains a pintle that closes off an orifice at
the nozzle end. When electric current is supplied 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 pressure, a
fine spray is developed in the shape of a pencil
stream. The spraying action atomizes the fuel, add-
ing it to the air entering the combustion chamber.
The nozzle (outlet) ends of the injectors are posi-
tioned into openings in the intake manifold just
above the intake valve ports of the cylinder head.
The engine wiring harness connector for each fuel
injector is equipped with an attached numerical tag
(INJ 1, INJ 2 etc.). This is used to identify each fuel
injector.
The injectors are energized individually in a
sequential order by the Powertrain Control Module(PCM). The PCM will adjust injector pulse width by
switching the ground path to each individual injector
on and off. Injector pulse width is the period of time
that the injector is energized. The PCM will adjust
injector pulse width based on various inputs it
receives.
Battery voltage is supplied to the injectors through
the ASD relay.
The PCM determines injector pulse width based on
various inputs.
OPERATION - PCM OUTPUT
The nozzle ends of the injectors are positioned into
openings in the intake manifold just above the intake
valve ports of the cylinder head. The engine wiring
harness connector for each fuel injector is equipped
with an attached numerical tag (INJ 1, INJ 2 etc.).
This is used to identify each fuel injector with its
respective cylinder number.
The injectors are energized individually in a
sequential order by the Powertrain Control Module
(PCM). The PCM will adjust injector pulse width by
switching the ground path to each individual injector
on and off. Injector pulse width is the period of time
that the injector is energized. The PCM will adjust
injector pulse width based on various inputs it
receives.
Battery voltage (12 volts +) is supplied to the injec-
tors through the ASD relay. The ASD relay will shut-
down the 12 volt power source to the fuel injectors if
the PCM senses the ignition is on, but the engine is
not running. This occurs after the engine has not
been running for approximately 1.8 seconds.
The PCM determines injector on-time (pulse width)
based on various inputs.
DIAGNOSIS AND TESTING - FUEL INJECTOR
To perform a complete test of the fuel injectors and
their circuitry, use the DRB scan tool and refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the injector only, refer to the following:
Disconnect the fuel injector wire harness connector
from the injector. The injector is equipped with 2
electrical terminals (pins). Place an ohmmeter across
the terminals. Resistance reading should be approxi-
mately 12 ohms  1.2 ohms at 20ÉC (68ÉF).
Fig. 9 FUEL INJECTOR Ð TYPICAL
KJFUEL INJECTION 14 - 33

IDLE AIR CONTROL MOTOR
DESCRIPTION
The IAC stepper motor is mounted to the throttle
body, and regulates the amount of air bypassing the
control of the throttle plate. As engine loads and
ambient temperatures change, engine rpm changes.
A pintle on the IAC stepper motor protrudes into a
passage in the throttle body, controlling air flow
through the passage. The IAC is controlled by the
Powertrain Control Module (PCM) to maintain the
target engine idle speed.
OPERATION
At idle, engine speed can be increased by retract-
ing the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by
restricting the passage with the pintle and diminish-
ing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is
moved (rotated) in steps, or increments. Opening the
IAC opens an air passage around the throttle blade
which increases RPM.
The PCM uses the IAC motor to control idle speed
(along with timing) and to reach a desired MAP dur-
ing decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of
the wires are for 12 volts and ground to supply elec-
trical current to the motor windings to operate the
stepper motor in one direction. The other 2 wires are
also for 12 volts and ground to supply electrical cur-
rent to operate the stepper motor in the opposite
direction.
To make the IAC go in the opposite direction, the
PCM just reverses polarity on both windings. If only
1 wire is open, the IAC can only be moved 1 step
(increment) in either direction. To keep the IAC
motor in position when no movement is needed, the
PCM will energize both windings at the same time.
This locks the IAC motor in place.
In the IAC motor system, the PCM will count
every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the
memory is cleared, the PCM no longer knows the
position of the pintle. So at the first key ON, the
PCM drives the IAC motor closed, regardless of
where it was before. This zeros the counter. Fromthis point the PCM will back out the IAC motor and
keep track of its position again.
When engine rpm is above idle speed, the IAC is
used for the following:
²Off-idle dashpot (throttle blade will close quickly
but idle speed will not stop quickly)
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)
²Power steering load control
The PCM can control polarity of the circuit to con-
trol direction of the stepper motor.
IAC Stepper Motor Program:The PCM is also
equipped with a memory program that records the
number of steps the IAC stepper motor most recently
advanced to during a certain set of parameters. For
example: The PCM was attempting to maintain a
1000 rpm target during a cold start-up cycle. The last
recorded number of steps for that may have been
125. That value would be recorded in the memory
cell so that the next time the PCM recognizes the
identical conditions, the PCM recalls that 125 steps
were required to maintain the target. This program
allows for greater customer satisfaction due to
greater control of engine idle.
Another function of the memory program, which
occurs when the power steering switch (if equipped),
or the A/C request circuit, requires that the IAC step-
per motor control engine rpm, is the recording of the
last targeted steps into the memory cell. The PCM
can anticipate A/C compressor loads. This is accom-
plished by delaying compressor operation for approx-
imately 0.5 seconds until the PCM moves the IAC
stepper motor to the recorded steps that were loaded
into the memory cell. Using this program helps elim-
inate idle-quality changes as loads change. Finally,
the PCM incorporates a9No-Load9engine speed lim-
iter of approximately 1800 - 2000 rpm, when it rec-
ognizes that the TPS is indicating an idle signal and
IAC motor cannot maintain engine idle.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the IAC motor through the PCM.
KJFUEL INJECTION 14 - 35

REMOVAL
2.4L
The Idle Air Control (IAC) motor is located on the
rear side of the throttle body (Fig. 12).
(1) Disconnect electrical connector from IAC motor.
(2) Remove two mounting bolts (screws).
(3) Remove IAC motor from throttle body.
3.7L
The Idle Air Control (IAC) motor is located on the
side of the throttle body (Fig. 13).
(1) Disconnect electrical connector from IAC motor.
(2) Remove two mounting bolts (screws).
(3) Remove IAC motor from throttle body.
INSTALLATION
2.4L
The Idle Air Control (IAC) motor is located on the
rear side of the throttle body.
(1) Install IAC motor to throttle body.
(2) Install and tighten two mounting bolts (screws)
to 7 N´m (60 in. lbs.) torque.
(3) Install electrical connector.
3.7L
The Idle Air Control (IAC) motor is located on the
side of the throttle body (Fig. 13).
(1) Install IAC motor to throttle body.(2) Install and tighten two mounting bolts (screws)
to 7 N´m (60 in. lbs.) torque.
(3) Install electrical connector.
INTAKE AIR TEMPERATURE
SENSOR
DESCRIPTION
The 2±wire Intake Manifold Air Temperature (IAT)
sensor is installed in the intake manifold with the
sensor element extending into the air stream.
The IAT sensor is a two-wire Negative Thermal
Coefficient (NTC) sensor. Meaning, as intake mani-
fold temperature increases, resistance (voltage) in the
sensor decreases. As temperature decreases, resis-
tance (voltage) in the sensor increases.
OPERATION
The IAT sensor provides an input voltage to the
Powertrain Control Module (PCM) indicating the
density of the air entering the intake manifold based
upon intake manifold temperature. At key-on, a
5±volt power circuit is supplied to the sensor from
the PCM. The sensor is grounded at the PCM
through a low-noise, sensor-return circuit.
The PCM uses this input to calculate the following:
²Injector pulse-width
²Adjustment of spark timing (to help prevent
spark knock with high intake manifold air-charge
temperatures)
Fig. 12 TPS/IAC MOTOR - 2.4L
1 - THROTTLE POSITION SENSOR (TPS)
2 - MOUNTING SCREWS
3 - IDLE AIR CONTROL MOTOR (IAC)
4 - MOUNTING SCREWS
Fig. 13 TPS/IAC MOTOR - 3.7L
1 - THROTTLE POSITION SENSOR (TPS)
2 - MOUNTING SCREWS
3 - IDLE AIR CONTROL MOTOR (IAC)
4 - MOUNTING SCREWS
14 - 36 FUEL INJECTIONKJ
IDLE AIR CONTROL MOTOR (Continued)

INSTALLATION
2.4L
The Manifold Absolute Pressure (MAP) sensor is
mounted into the rear of the intake manifold. An
o-ring is used to seal the sensor to the intake mani-
fold (Fig. 19).
(1) Clean MAP sensor mounting hole at intake
manifold.
(2) Check MAP sensor o-ring seal for cuts or tears.
(3) Position sensor into manifold.
(4) Install MAP sensor mounting screws. Tighten
screw to 3 N´m (25 in. lbs.) torque.
(5) Connect electrical connector.
3.7L
The Manifold Absolute Pressure (MAP) sensor is
mounted into the front of the intake manifold (Fig.
18). An o-ring is used to seal the sensor to the intake
manifold (Fig. 19).
(1) Clean MAP sensor mounting hole at intake
manifold.
(2) Check MAP sensor o-ring seal for cuts or tears.
(3) Position sensor into manifold.
(4) Install MAP sensor mounting bolts (screws).
Tighten screws to 3 N´m (25 in. lbs.) torque.
(5) Connect electrical connector.
OXYGEN SENSOR
DESCRIPTION
The Oxygen Sensors (O2S) are attached to, and
protrude into the vehicle exhaust system. Depending
on the engine or emission package, the vehicle may
use a total of either 2 or 4 sensors.
2.4L Engine:Two sensors are used: upstream
(referred to as 1/1) and downstream (referred to as
1/2). With this emission package, the upstream sen-
sor (1/1) is located just before the main catalytic con-
vertor. The downstream sensor (1/2) is located just
after the main catalytic convertor.
3.7L V-6 Engine:On this emissions package, 4
sensors are used: 2 upstream (referred to as 1/1 and
2/1) and 2 downstream (referred to as 1/2 and 2/2).
With this emission package, the right upstream sen-
sor (2/1) is located in the right exhaust downpipe just
before the mini-catalytic convertor. The left upstream
sensor (1/1) is located in the left exhaust downpipe
just before the mini-catalytic convertor. The right
downstream sensor (2/2) is located in the right
exhaust downpipe just after the mini-catalytic con-
vertor, and before the main catalytic convertor. The
left downstream sensor (1/2) is located in the left
exhaust downpipe just after the mini-catalytic con-
vertor, and before the main catalytic convertor.
OPERATION
An O2 sensor is a galvanic battery that provides
the PCM with a voltage signal (0-1 volt) inversely
proportional to the amount of oxygen in the exhaust.
In other words, if the oxygen content is low, the volt-
age output is high; if the oxygen content is high the
output voltage is low. The PCM uses this information
to adjust injector pulse-width to achieve the
14.7±to±1 air/fuel ratio necessary for proper engine
operation and to control emissions.
The O2 sensor must have a source of oxygen from
outside of the exhaust stream for comparison. Cur-
rent O2 sensors receive their fresh oxygen (outside
air) supply through the O2 sensor case housing.
Four wires (circuits) are used on each O2 sensor: a
12±volt feed circuit for the sensor heating element; a
ground circuit for the heater element; a low-noise
sensor return circuit to the PCM, and an input cir-
cuit from the sensor back to the PCM to detect sen-
sor operation.
Oxygen Sensor Heater Relay - 3.7L Engine:On
the 3.7L engine, 4 heated oxygen sensors are used. A
separate oxygen sensor relay is used to supply volt-
age to the sensors heating elements for only the 1/2
and 2/2 downstream sensors. Voltage for the other 2
sensor heating elements is supplied directly from the
Powertrain Control Module (PCM) through a Pulse
Width Module (PWM) method.
Pulse Width Module (PWM):Voltage to the O2
sensor heating elements is supplied directly from the
Powertrain Control Module (PCM) through two sepa-
rate Pulse Width Module (PWM) low side drivers.
PWM is used on both the upstream and downstream
O2 sensors on the 2.4L engine, and only on the 2
upstream sensors (1/1 and 2/1) on the 3.7L engine.
The main objective for a PWM driver is to avoid over-
heating of the O2 sensor heater element. With
exhaust temperatures increasing with time and
engine speed, it's not required to have a full-voltage
duty-cycle on the O2 heater elements.
To avoid the large simultaneous current surge
needed to operate all 4 sensors, power is delayed to
the 2 downstream heater elements by the PCM for
approximately 2 seconds.
Oxygen Sensor Heater Elements:
The O2 sensor uses a Positive Thermal Co-efficient
(PTC) heater element. As temperature increases,
resistance increases. At ambient temperatures
around 70ÉF, the resistance of the heating element is
approximately 4.5 ohms. As the sensor's temperature
increases, resistance in the heater element increases.
This allows the heater to maintain the optimum
operating temperature of approximately 930É-1100ÉF
(500É-600É C). Although the sensors operate the
same, there are physical differences, due to the envi-
14 - 40 FUEL INJECTIONKJ
MAP SENSOR (Continued)

WARNING: THE EXHAUST MANIFOLD, EXHAUST
PIPES AND CATALYTIC CONVERTER BECOME
VERY HOT DURING ENGINE OPERATION. ALLOW
ENGINE TO COOL BEFORE REMOVING OXYGEN
SENSOR.
(1) Raise and support vehicle.
(2) Disconnect wire connector from O2S sensor.
CAUTION: When disconnecting sensor electrical
connector, do not pull directly on wire going into
sensor.
(3) Remove O2S sensor with an oxygen sensor
removal and installation tool.
(4) Clean threads in exhaust pipe using appropri-
ate tap.
INSTALLATION
Threads of new oxygen sensors are factory coated
with anti-seize compound to aid in removal.DO
NOT add any additional anti-seize compound to
threads of a new oxygen sensor.
(1) Install O2S sensor. Tighten to 30 N´m (22 ft.
lbs.) torque.
(2) Connect O2S sensor wire connector.
(3) Lower vehicle.
THROTTLE BODY
DESCRIPTION
The throttle body is located on the intake manifold.
Fuel does not enter the intake manifold through the
throttle body. Fuel is sprayed into the manifold by
the fuel injectors.
OPERATION
Filtered air from the air cleaner enters the intake
manifold through the throttle body. The throttle body
contains an air control passage controlled by an Idle
Air Control (IAC) motor. The air control passage is
used to supply air for idle conditions. A throttle valve
(plate) is used to supply air for above idle conditions.
Certain sensors are attached to the throttle body.
The accelerator pedal cable, speed control cable and
transmission control cable (when equipped) are con-
nected to the throttle body linkage arm.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the PCM.
REMOVAL
2.4L
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the Powertrain Control Module (PCM).
(1) Remove air cleaner tube at throttle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS.
(3) Remove all control cables from throttle body
(lever) arm. Refer to the Accelerator Pedal and Throt-
tle Cable section for removal/installation procedures.
(4) Disconnect necessary vacuum lines at throttle
body.
(5) Remove 3 throttle body mounting bolts (Fig.
23).
(6) Remove throttle body from intake manifold.
(7) Check condition of old throttle body-to-intake
manifold o-ring.
3.7L
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the Powertrain Control Module (PCM).
(1) Remove air cleaner tube at throttle body.
(2) Disconnect throttle body electrical connectors
at IAC motor and TPS.
Fig. 23 THROTTLE BODY MOUNTING BOLTS - 2.4L
1 - THROTTLE BODY
2 - IGNITION COIL
3 - MOUNTING BOLTS (3)
KJFUEL INJECTION 14 - 43
OXYGEN SENSOR (Continued)