2002 JEEP LIBERTY Bus

(6) Install oil pressure switch and connector. (Refer
to 9 - ENGINE/LUBRICATION/OIL PRESSURE
SENSOR/SWITCH - INSTALLATION)
OIL
STANDARD PROCEDURE
ENGINE OIL LEVEL CHECK
The best time to check engine oil level is after it
has sat overnight, or if the engine has been running,
allow the engine to be shut off for at least 5 minutes
before checking oil level.
Checking the oil while the vehicle is on level
ground will improve the accuracy of the oil level
reading. Remove dipstick and observe oil level. Add
oil only when the level is at or below the ADD mark
(Fig. 78).
STANDARD PROCEDURE - ENGINE OIL AND
FILTER CHANGE
Change engine oil at mileage and time intervals
described in the Maintenance Schedule. (Refer to
LUBRICATION & MAINTENANCE/MAINTE-
NANCE SCHEDULES - DESCRIPTION)
WARNING: NEW OR USED ENGINE OIL CAN BE
IRRITATING TO THE SKIN. AVOID PROLONGED OR
REPEATED SKIN CONTACT WITH ENGINE OIL.
CONTAMINANTS IN USED ENGINE OIL, CAUSED BY
INTERNAL COMBUSTION, CAN BE HAZARDOUS TO
YOUR HEALTH. THOROUGHLY WASH EXPOSED
SKIN WITH SOAP AND WATER. DO NOT WASH
SKIN WITH GASOLINE, DIESEL FUEL, THINNER, OR
SOLVENTS, HEALTH PROBLEMS CAN RESULT. DO
NOT POLLUTE, DISPOSE OF USED ENGINE OIL
PROPERLY. CONTACT YOUR DEALER OR GOVERN-
MENT AGENCY FOR LOCATION OF COLLECTION
CENTER IN YOUR AREA.
Run engine until achieving normal operating tem-
perature.
(1) Position the vehicle on a level surface and turn
engine off.(2) Hoist and support vehicle on safety stands.
Refer to Hoisting and Jacking Recommendations.
(Refer to LUBRICATION & MAINTENANCE/HOIST-
ING - STANDARD PROCEDURE)
(3) Remove oil fill cap.
(4) Place a suitable drain pan under crankcase
drain.
(5) Remove drain plug from crankcase and allow
oil to drain into pan. Inspect drain plug threads for
stretching or other damage. Replace drain plug and
gasket if damaged.
(6) Remove oil filter. (Refer to 9 - ENGINE/LUBRI-
CATION/OIL FILTER - REMOVAL)
(7) Install and tighten drain plug in crankcase.
(8) Install new oil filter. (Refer to 9 - ENGINE/LU-
BRICATION/OIL FILTER - INSTALLATION)
(9) Lower vehicle and fill crankcase with specified
type and amount of engine oil. (Refer to LUBRICA-
TION & MAINTENANCE/FLUID TYPES -
DESCRIPTION)
(10) Install oil fill cap.
(11) Start engine and inspect for leaks.
(12) Stop engine and inspect oil level.
NOTE: Care should be exercised when disposing
used engine oil after it has been drained from a
vehicle engine. Refer to the WARNING listed above.
OIL FILTER
DESCRIPTION
The engine oil filter is a high quality full-flow, dis-
posable type. Replace the oil filter with a Mopartor
the equivalent.
REMOVAL
(1) Raise vehicle on hoist.
(2) Position an oil collecting container under oil fil-
ter location.
CAUTION: When servicing the oil filter avoid
deforming the filter can by installing the remove/in-
stall tool band strap against the can to base lock
seam. The lock seam joining the can to the base is
reinforced by the base plate.
(3) Using a suitable filter wrench, turn oil filter
counterclockwise to remove (Fig. 79).
INSTALLATION
(1) Clean and check filter mounting surface. The
surface must be smooth, flat and free of debris or
pieces of gasket.
(2) Lubricate new oil filter gasket with clean
engine oil.
Fig. 78 Oil Level
1 - ENGINE OIL LEVEL DIPSTICK
KJENGINE9s-47
LUBRICATION (Continued)

(3) Screw oil filter on until the gasket contacts
base. Tighten to 21 N´m (15 ft. lbs.).
OIL PAN
REMOVAL
(1) Remove air cleaner assembly.
(2) Raise vehicle on hoist and drain engine oil.
(3) Loosen the engine mount thru bolts.
(4) Disconnect exhaust pipe at manifold.
(5) Remove structural collar, if equipped.
(6) Remove front axle mounting bolts, and lower
axle as far possible, if equipped.
(7) Using suitable jack, raise engine as needed.
(8) Remove oil pan attaching bolts.
(9) Remove oil pan.
(10) Clean oil pan and all gasket surfaces.
INSTALLATION
(1) Install the oil pan gasket to the block.
(2) Apply a 3MM (1/8 inch) bead of MopartEngine
RTV at the oil pump to engine block parting line
(Fig. 80).
(3) Install pan and tighten the screws to 12 N´m
(105 in. lbs.).
(4) Lower engine, and remove jack.
(5) Tighten engine mount thru bolts.
(6) Raise the front axle into position, and reinstall
front axle mounting bolts. If equipped.
(7) Reconnect exhaust pipe to manifold.
(8) Install structural collar, if equipped.
(9) Lower vehicle.(10) Fill engine crankcase with proper oil to cor-
rect level.
(11) Reinstall air cleaner assembly.
OIL PRESSURE SENSOR/
SWITCH
DESCRIPTION
The 3±wire, electrical/mechanical engine oil pres-
sure sensor (sending unit) is located in an engine oil
pressure gallery.
OPERATION
The oil pressure sensor uses three circuits. They
are:
²A 5±volt power supply from the Powertrain Con-
trol Module (PCM)
²A sensor ground through the PCM's sensor
return
²A signal to the PCM relating to engine oil pres-
sure
The oil pressure sensor has a 3±wire electrical
function very much like the Manifold Absolute Pres-
sure (MAP) sensor. Meaning different pressures
relate to different output voltages.
A 5±volt supply is sent to the sensor from the PCM
to power up the sensor. The sensor returns a voltage
signal back to the PCM relating to engine oil pres-
sure. This signal is then transferred (bussed) to the
Fig. 79 2.4 OIL FILTERFig. 80 OIL PAN GASKET INSTALLATION
1 - SEALER LOCATION
9s - 48 ENGINEKJ
OIL FILTER (Continued)

instrument panel on either a CCD or PCI bus circuit
(depending on vehicle line) to operate the oil pressure
gauge and the check gauges lamp. Ground for the
sensor is provided by the PCM through a low-noise
sensor return.
OIL PUMP
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove timing belt. (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - REMOVAL)
(3) Remove timing belt rear cover. (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - REMOVAL)
(4) Remove oil pan. (Refer to 9 - ENGINE/LUBRI-
CATION/OIL PAN - REMOVAL)
(5) Remove crankshaft sprocket using Special
Tools 6793 and C-4685-C2 (Fig. 81).
(6) Remove crankshaft key (Fig. 82).
(7) Remove oil pick-up tube.
(8) Remove oil pump (Fig. 83) and front crankshaft
seal.
DISASSEMBLY
(1) To remove the relief valve, proceed as follows:
(a) Remove the threaded plug and gasket from
the oil pump.
(b) Remove spring and relief valve.
(2) Remove oil pump cover fasteners, and lift off
cover.
(3) Remove pump rotors.
(4) Wash all parts in a suitable solvent and
inspect carefully for damage or wear.
CLEANING
(1) Clean all parts thoroughly in a suitable sol-
vent.
Fig. 81 Crankshaft Sprocket - Removal
1 - SPECIAL TOOL 6793
2 - SPECIAL TOOL C-4685±C2
3 - CRANKSHAFT SPROCKET
Fig. 82 Crankshaft Key
1 - CRANKSHAFT KEY
Fig. 83 2.4L OIL PUMP
1 - BOLTS
2 - BOLTS
KJENGINE9s-49
OIL PRESSURE SENSOR/SWITCH (Continued)

(7) Install crankshaft sprocket using Special Tool
6792 (Fig. 89).
(8) Install oil pump pick-up tube.(9) Install oil pan. (Refer to 9 - ENGINE/LUBRI-
CATION/OIL PAN - INSTALLATION)
(10) Install timing belt rear cover. (Refer to 9 -
ENGINE/VALVE TIMING/TIMING BELT / CHAIN
COVER(S) - INSTALLATION)
(11) Install timing belt. (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - INSTALLATION)
INTAKE MANIFOLD
DESCRIPTION
The intake manifold is a one piece composite mod-
ule that attaches to the cylinder head with fasteners.
The manifold is a long branch design to enhance low
and mid-range torque
OPERATION
The intake manifold delivers air to the combustion
chambers. This air allows the fuel delivered by the
fuel injectors to ignite when the spark plug fire.
DIAGNOSIS AND TESTING - INTAKE
MANIFOLD LEAKS
An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
(1) Start the engine.
Fig. 87 Oil Pump Sealing - Typical
1 - O-RING
2 - SEALER LOCATION
Fig. 88 Front Crankshaft Seal - Installation
1 - PROTECTOR
2 - SEAL
3 - SPECIAL TOOL 6780
Fig. 89 Crankshaft Sprocket - Installation
1 - SPECIAL TOOL 6792
2 - TIGHTEN NUT TO INSTALL
KJENGINE9s-51
OIL PUMP (Continued)

EXHAUST MANIFOLD
DESCRIPTION
The exhaust manifold is made of Hi-Silicone Moly
nodular cast iron for strength and high tempera-
tures. The manifold attaches to the cylinder head.
OPERATION
The exhaust manifold collects the exhaust gasses
exiting the combustion chambers. Then it channels
the exhaust gasses to the exhaust pipe attached to
the manifold.
REMOVAL
(1) Raise vehicle and disconnect exhaust pipe from
the exhaust manifold.
(2) Lower the vehicle.
(3) Disconnect upstream oxygen sensor connector
at the rear of exhaust manifold.
(4) Remove the air cleaner bracket (Fig. 91).
(5) Remove the heat shield.
(6) Remove the bolts attaching the manifold to the
cylinder head.
(7) Remove exhaust manifold.
(8) Inspect the manifold. (Refer to 9 - ENGINE/
MANIFOLDS/EXHAUST MANIFOLD - INSPEC-
TION)
CLEANING
(1) Discard gasket (if equipped) and clean all sur-
faces of manifold and cylinder head.
INSPECTION
(1) Inspect manifold gasket surfaces for flatness
with straight edge. Surface must be flat within 0.15
mm per 300 mm (0.006 in. per foot) of manifold
length.
(2) Inspect manifolds for cracks or distortion.
Replace manifold as necessary.
INSTALLATION
(1) Clean the manifold mating surfaces.
(2) Install exhaust manifold with a new gasket.
Tighten attaching nuts to 20 N´m (175 in. lbs.).
(3) Attach exhaust pipe to exhaust manifold and
tighten fasteners to 37 N´m (27 ft. lbs.).
(4) Install and connect the oxygen sensor. (Refer to
14 - FUEL SYSTEM/FUEL INJECTION/O2 SENSOR
- COMPONENT LOCATION)
(5) Install the heat shield.
(6) Install the air cleaner bracket.
TIMING BELT COVER(S)
REMOVAL
FRONT COVER
(1) Remove crankshaft vibration damper. (Refer to
9 - ENGINE/ENGINE BLOCK/VIBRATION
DAMPER - REMOVAL)
(2) Remove generator drive belt tensioner assem-
bly. (Refer to 7 - COOLING/ACCESSORY DRIVE/
BELT TENSIONERS - REMOVAL)
(3) Remove timing belt front cover bolts, and
remove covers.
REAR COVER
(1) Remove front covers.
(2) Remove timing belt. (Refer to 9 - ENGINE/
VALVE TIMING/TIMING BELT/CHAIN AND
SPROCKETS - REMOVAL)
(3) Hold camshaft sprocket with Special Tool 6847
while removing center bolt.
(4) Remove timing belt idler pulley.
(5) Remove rear cover fasteners and remove cover
from engine.
INSTALLATION
REAR COVER
(1) Install timing belt rear cover and bolts (Fig.
92). Torque bolts to 12 N´m (105 in. lbs).
Fig. 91 AIR CLEANER BRACKET
1 - AIR CLEANER BRACKET
2 - BOLT (2)
KJENGINE9s-53

FUEL LEVEL SENDING UNIT /
SENSOR
DESCRIPTION
The fuel gauge sending unit (fuel level sensor) is
attached to the side of the fuel pump module. The
sending unit consists of a float, an arm, and a vari-
able resistor track (card).
OPERATION
The fuel pump module has 4 different circuits
(wires). Two of these circuits are used for the fuel
gauge sending unit for fuel gauge operation, and for
certain OBD II emission requirements. The other 2
wires are used for electric fuel pump operation.
For Fuel Gauge Operation:A constant current
source of approximately 32 milliamps is supplied to
the resistor track on the fuel gauge sending unit.
This is fed directly from the Powertrain Control Mod-
ule (PCM).NOTE: For diagnostic purposes, this
12V power source can only be verified with the
circuit opened (fuel pump module electrical
connector unplugged). With the connectors
plugged, output voltages will vary from about
0.6 volts at FULL, to about 8.6 volts at EMPTY
(about 8.6 volts at EMPTY for Jeep models, and
about 7.0 volts at EMPTY for Dodge Truck mod-
els).The resistor track is used to vary the voltage
(resistance) depending on fuel tank float level. As
fuel level increases, the float and arm move up,
which decreases voltage. As fuel level decreases, the
float and arm move down, which increases voltage.
The varied voltage signal is returned back to the
PCM through the sensor return circuit.
Both of the electrical circuits between the fuel
gauge sending unit and the PCM are hard-wired (not
multi-plexed). After the voltage signal is sent from
the resistor track, and back to the PCM, the PCM
will interpret the resistance (voltage) data and send
a message across the multi-plex bus circuits to the
instrument panel cluster. Here it is translated into
the appropriate fuel gauge level reading. Refer to
Instrument Panel for additional information.
For OBD II Emission Monitor Requirements:
The PCM will monitor the voltage output sent from
the resistor track on the sending unit to indicate fuel
level. The purpose of this feature is to prevent the
OBD II system from recording/setting false misfire
and fuel system monitor diagnostic trouble codes.
The feature is activated if the fuel level in the tank
is less than approximately 15 percent of its rated
capacity. If equipped with a Leak Detection Pump
(EVAP system monitor), this feature will also be acti-
vated if the fuel level in the tank is more than
approximately 85 percent of its rated capacity.
DIAGNOSIS AND TESTING - FUEL LEVEL
SENDING UNIT
The fuel level sending unit contains a variable
resistor (track). As the float moves up or down, elec-
trical resistance will change. Refer to Instrument
Panel and Gauges for Fuel Gauge testing. To test the
gauge sending unit only, it must be removed from
vehicle. The unit is a separate part of the lower fuel
pump module section. Refer to Fuel Pump Module
Removal/Installation for procedures (remove only the
upper section of the fuel pump module). Measure the
resistance across the sending unit terminals. With
float in up position, resistance should be 20 ohms (+/-
5%). With float in down position, resistance should be
270 ohms (+/- 5%).
REMOVAL
The fuel level sending unit (fuel level sensor) and
float assembly is located on the side of the lower sec-
tion of the fuel pump module. The lower section of
the fuel pump module is located within the fuel tank.
(1) Remove lower section of fuel pump module
from fuel tank. Refer to Fuel Pump Module Removal/
Installation.
(2) To remove sending unit from pump module, lift
on plastic locking tab (Fig. 8) while sliding sending
unit upwards.
(3) Disconnect 4±wire electrical connector (Fig. 9)
from bottom of upper section of fuel pump module.
Separate necessary sending unit wiring.
Fig. 8 FUEL LEVEL SENDING UNIT
1 - LIFT TAB HERE FOR REMOVAL
2 - FUEL LEVEL SENDING UNIT
3 - LOWER SECTION OF PUMP MODULE
KJFUEL DELIVERY 14 - 9

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

INSTALLATION
2.4L
The intake manifold air temperature (IAT) sensor
is installed into the intake manifold plenum at the
rear end of the intake manifold.
(1) Check condition of sensor o-ring.
(2) Clean sensor mounting hole in intake manifold.
(3) Position sensor into intake manifold and rotate
clockwise until past release tab.
(4) Install electrical connector.
3.7L
The intake manifold air temperature (IAT) sensor
is installed into the left side of intake manifold ple-
num (Fig. 16).
(1) Check condition of sensor o-ring.
(2) Clean sensor mounting hole in intake manifold.
(3) Position sensor into intake manifold and rotate
clockwise until past release tab (Fig. 16).
(4) Install electrical connector.
MAP SENSOR
DESCRIPTION
2.4L
The Manifold Absolute Pressure (MAP) sensor is
mounted into the rear of the intake manifold with 1
screw.
3.7L
The Manifold Absolute Pressure (MAP) sensor is
mounted into the front of the intake manifold with 2
screws.
OPERATION
The MAP sensor is used as an input to the Power-
train Control Module (PCM). It contains a silicon
based sensing unit to provide data on the manifold
vacuum that draws the air/fuel mixture into the com-
bustion chamber. The PCM requires this information
to determine injector pulse width and spark advance.
When manifold absolute pressure (MAP) equals
Barometric pressure, the pulse width will be at max-
imum.
A 5 volt reference is supplied from the PCM and
returns a voltage signal to the PCM that reflects
manifold pressure. The zero pressure reading is 0.5V
and full scale is 4.5V. For a pressure swing of 0±15
psi, the voltage changes 4.0V. To operate the sensor,
it is supplied a regulated 4.8 to 5.1 volts. Ground is
provided through the low-noise, sensor return circuit
at the PCM.The MAP sensor input is the number one contrib-
utor to fuel injector pulse width. The most important
function of the MAP sensor is to determine baromet-
ric pressure. The PCM needs to know if the vehicle is
at sea level or at a higher altitude, because the air
density changes with altitude. It will also help to cor-
rect for varying barometric pressure. Barometric
pressure and altitude have a direct inverse correla-
tion; as altitude goes up, barometric goes down. At
key-on, the PCM powers up and looks at MAP volt-
age, and based upon the voltage it sees, it knows the
current barometric pressure (relative to altitude).
Once the engine starts, the PCM looks at the voltage
again, continuously every 12 milliseconds, and com-
pares the current voltage to what it was at key-on.
The difference between current voltage and what it
was at key-on, is manifold vacuum.
During key-on (engine not running) the sensor
reads (updates) barometric pressure. A normal range
can be obtained by monitoring a known good sensor.
As the altitude increases, the air becomes thinner
(less oxygen). If a vehicle is started and driven to a
very different altitude than where it was at key-on,
the barometric pressure needs to be updated. Any
time the PCM sees Wide Open Throttle (WOT), based
upon Throttle Position Sensor (TPS) angle and RPM,
it will update barometric pressure in the MAP mem-
ory cell. With periodic updates, the PCM can make
its calculations more effectively.
The PCM uses the MAP sensor input to aid in cal-
culating the following:
²Manifold pressure
²Barometric pressure
²Engine load
²Injector pulse-width
²Spark-advance programs
²Shift-point strategies (certain automatic trans-
missions only)
²Idle speed
²Decel fuel shutoff
The MAP sensor signal is provided from a single
piezoresistive element located in the center of a dia-
phragm. The element and diaphragm are both made
of silicone. As manifold pressure changes, the dia-
phragm moves causing the element to deflect, which
stresses the silicone. When silicone is exposed to
stress, its resistance changes. As manifold vacuum
increases, the MAP sensor input voltage decreases
proportionally. The sensor also contains electronics
that condition the signal and provide temperature
compensation.
The PCM recognizes a decrease in manifold pres-
sure by monitoring a decrease in voltage from the
reading stored in the barometric pressure memory
cell. The MAP sensor is a linear sensor; meaning as
pressure changes, voltage changes proportionately.
14 - 38 FUEL INJECTIONKJ
INTAKE AIR TEMPERATURE SENSOR (Continued)