2002 JEEP LIBERTY ECU

ENGINE SYSTEMS
TABLE OF CONTENTS
page page
BATTERY SYSTEM......................... 1
CHARGING SYSTEM....................... 22STARTING SYSTEM....................... 32
BATTERY SYSTEM
TABLE OF CONTENTS
page page
BATTERY SYSTEM
DESCRIPTION..........................1
OPERATION............................2
DIAGNOSIS AND TESTING - BATTERY
SYSTEM.............................2
CLEANING.............................5
INSPECTION...........................6
SPECIFICATIONS........................6
SPECIAL TOOLS........................7
BATTERY
DESCRIPTION..........................7
DIAGNOSIS AND TESTING - BATTERY.......8
STANDARD PROCEDURE
STANDARD PROCEDURE - BATTERY
CHARGING...........................8
STANDARD PROCEDURE - BUILT-IN
INDICATOR TEST.....................10
STANDARD PROCEDURE - HYDROMETER
TEST...............................11
STANDARD PROCEDURE - OPEN-CIRCUIT
VOLTAGE TEST.......................12
STANDARD PROCEDURE - LOAD TEST....12
STANDARD PROCEDURE - IGNITION-OFF
DRAW TEST.........................14STANDARD PROCEDURE - USING
MIDTRONICS ELECTRICAL TESTER.......15
REMOVAL.............................16
INSTALLATION.........................16
BATTERY HOLDDOWN
DESCRIPTION.........................17
OPERATION...........................17
REMOVAL.............................17
INSTALLATION.........................17
BATTERY CABLES
DESCRIPTION.........................18
OPERATION...........................18
DIAGNOSIS AND TESTING - BATTERY
CABLES............................19
THERMAL GUARD
DESCRIPTION.........................20
OPERATION...........................20
REMOVAL.............................20
INSTALLATION.........................20
BATTERY TRAY
DESCRIPTION.........................21
OPERATION...........................21
REMOVAL.............................21
INSTALLATION.........................21
BATTERY SYSTEM
DESCRIPTION
A single 12-volt battery system is standard factory-
installed equipment on this model. All of the compo-
nents of the battery system are located within the
engine compartment of the vehicle. The service infor-
mation for the battery system in this vehicle covers
the following related components, which are covered
in further detail elsewhere in this service manual:²Battery- The storage battery provides a reli-
able means of storing a renewable source of electrical
energy within the vehicle.
²Battery Cable- The battery cables connect the
battery terminal posts to the vehicle electrical sys-
tem.
²Battery Holddown- The battery holddown
hardware secures the battery in the battery tray in
the engine compartment.
KJENGINE SYSTEMS 8F - 1

²Battery Thermal Guard- The battery thermal
guard insulates the battery to protect it from engine
compartment temperature extremes.
²Battery Tray- The battery tray provides a
secure mounting location in the vehicle for the bat-
tery and an anchor point for the battery holddown
hardware.
For battery system maintenance schedules and
jump starting procedures, see the owner's manual in
the vehicle glove box. Optionally, refer to Lubrication
and Maintenance for the proper battery jump start-
ing procedures. While battery charging can be consid-
ered a maintenance procedure, the battery charging
procedures and related information are located in the
service procedures section of this service manual.
This was done because the battery must be fully-
charged before any battery system diagnosis or test-
ing procedures can be performed. Refer to Standard
Procedures for the proper battery charging proce-
dures.
OPERATION
The battery system is designed to provide a safe,
efficient, reliable and mobile means of delivering and
storing electrical energy. This electrical energy is
required to operate the engine starting system, as
well as to operate many of the other vehicle acces-
sory systems for limited durations while the engine
and/or the charging system are not operating. The
battery system is also designed to provide a reserve
of electrical energy to supplement the charging sys-
tem for short durations while the engine is running
and the electrical current demands of the vehicle
exceed the output of the charging system. In addition
to delivering, and storing electrical energy for the
vehicle, the battery system serves as a capacitor and
voltage stabilizer for the vehicle electrical system. It
absorbs most abnormal or transient voltages caused
by the switching of any of the electrical components
or circuits in the vehicle.
DIAGNOSIS AND TESTING - BATTERY SYSTEM
The battery, starting, and charging systems in the
vehicle operate with one another and must be testedas a complete system. In order for the engine to start
and the battery to maintain its charge properly, all of
the components that are used in these systems must
perform within specifications. It is important that
the battery, starting, and charging systems be thor-
oughly tested and inspected any time a battery needs
to be charged or replaced. The cause of abnormal bat-
tery discharge, overcharging or early battery failure
must be diagnosed and corrected before a battery is
replaced and before a vehicle is returned to service.
The service information for these systems has been
separated within this service manual to make it eas-
ier to locate the specific information you are seeking.
However, when attempting to diagnose any of these
systems, it is important that you keep their interde-
pendency in mind.
The diagnostic procedures used for the battery,
starting, and charging systems include the most
basic conventional diagnostic methods, to the more
sophisticated On-Board Diagnostics (OBD) built into
the Powertrain Control Module (PCM). Use of an
induction-type milliampere ammeter, a volt/ohmme-
ter, a battery charger, a carbon pile rheostat (load
tester) and a 12-volt test lamp may be required. All
OBD-sensed systems are monitored by the PCM.
Each monitored circuit is assigned a Diagnostic Trou-
ble Code (DTC). The PCM will store a DTC in elec-
tronic memory for any failure it detects. Refer to
Charging System for the proper charging system on-
board diagnostic test procedures.
MIDTRONICS ELECTRICAL SYSTEM TESTER
The Midtronicstautomotive battery and charging
system tester is designed to help the dealership tech-
nicians diagnose the cause of a defective battery or
charging system. Follow the instruction manual sup-
plied with the tester to properly diagnose a vehicle. If
the instruction manual is not available refer to the
standard procedure in this section, which includes
the directions for using the midtronics electrical sys-
tem tester.
8F - 2 BATTERY SYSTEMKJ
BATTERY SYSTEM (Continued)

Test the specific gravity of the electrolyte in each
battery cell. If the specific gravity of all cells is above
1.235, but the variation between cells is more than
fifty points (0.050), the battery should be replaced. If
the specific gravity of one or more cells is less than
1.235, charge the battery at a rate of approximately
five amperes. Continue charging the battery until
three consecutive specific gravity tests, taken at one-
hour intervals, are constant. If the cell specific grav-
ity variation is more than fifty points (0.050) at the
end of the charge period, replace the battery.
When the specific gravity of all cells is above 1.235,
and the cell variation is less than fifty points (0.050),
the battery may be load tested to determine its
cranking capacity. Refer to Standard Procedures for
the proper battery load test procedures.
STANDARD PROCEDURE - OPEN-CIRCUIT
VOLTAGE TEST
A battery open-circuit voltage (no load) test will
show the approximate state-of-charge of a battery.
This test can be used in place of the hydrometer test
when a hydrometer is not available, or for mainte-
nance-free batteries with non-removable cell caps.
Before proceeding with this test, completely charge
the battery (Refer to 8 - ELECTRICAL/BATTERY
SYSTEM/BATTERY - STANDARD PROCEDURE).(1) Before measuring the open-circuit voltage, the
surface charge must be removed from the battery.
Turn on the headlamps for fifteen seconds, then
allow up to five minutes for the battery voltage to
stabilize.
(2) Disconnect and isolate both battery cables, neg-
ative cable first.
(3) Using a voltmeter connected to the battery
posts (see the instructions provided by the manufac-
turer of the voltmeter), measure the open-circuit volt-
age (Fig. 10).
See the Open-Circuit Voltage Table. This voltage
reading will indicate the battery state-of-charge, but
will not reveal its cranking capacity. If a battery has
an open-circuit voltage reading of 12.4 volts or
greater, it may be load tested to reveal its cranking
capacity (Refer to 8 - ELECTRICAL/BATTERY SYS-
TEM/BATTERY - STANDARD PROCEDURE).
OPEN CIRCUIT VOLTAGE TABLE
Open Circuit Voltage Charge Percentage
11.7 volts or less 0%
12.0 volts 25%
12.2 volts 50%
12.4 volts 75%
12.6 volts or more 100%
STANDARD PROCEDURE - LOAD TEST
A battery load test will verify the battery cranking
capacity. The test is based on the Cold Cranking
Amperage (CCA) rating of the battery. To determine
the battery CCA rating, see the label affixed to the
battery case or refer to Battery Specifications for the
proper factory-installed specifications.
Before proceeding with this test, completely charge
the battery (Refer to 8 - ELECTRICAL/BATTERY
SYSTEM/BATTERY - STANDARD PROCEDURE).
Fig. 9 Hydrometer - Typical
1 - BULB
2 - SURFACE COHESION
3 - SPECIFIC GRAVITY READING
4 - TEMPERATURE READING
5 - HYDROMETER BARREL
6 - FLOAT
Fig. 10 Testing Open-Circuit Voltage - Typical
8F - 12 BATTERY SYSTEMKJ
BATTERY (Continued)

(2) Determine that the underhood lamp is operat-
ing properly, then disconnect the lamp wire harness
connector or remove the lamp bulb.
(3) Disconnect the battery negative cable.
(4) Set an electronic digital multi-meter to its
highest amperage scale. Connect the multi-meter
between the disconnected battery negative cable ter-
minal clamp and the battery negative terminal post.
Make sure that the doors remain closed so that the
illuminated entry system is not activated. The multi-
meter amperage reading may remain high for up to
three minutes, or may not give any reading at all
while set in the highest amperage scale, depending
upon the electrical equipment in the vehicle. The
multi-meter leads must be securely clamped to the
battery negative cable terminal clamp and the bat-
tery negative terminal post. If continuity between the
battery negative terminal post and the negative cable
terminal clamp is lost during any part of the IOD
test, the electronic timer function will be activated
and all of the tests will have to be repeated.
(5) After about three minutes, the high-amperage
IOD reading on the multi-meter should become very
low or nonexistent, depending upon the electrical
equipment in the vehicle. If the amperage reading
remains high, remove and replace each fuse or circuit
breaker in the Power Distribution Center (PDC) and
then in the Junction Block (JB), one at a time until
the amperage reading becomes very low, or nonexist-
ent. Refer to the appropriate wiring information in
this service manual for complete PDC and JB fuse,
circuit breaker, and circuit identification. This will
isolate each circuit and identify the circuit that is the
source of the high-amperage IOD. If the amperage
reading remains high after removing and replacing
each fuse and circuit breaker, disconnect the wire
harness from the generator. If the amperage reading
now becomes very low or nonexistent, refer to Charg-
ing System for the proper charging system diagnosis
and testing procedures. After the high-amperage IOD
has been corrected, switch the multi-meter to pro-
gressively lower amperage scales and, if necessary,
repeat the fuse and circuit breaker remove-and-re-
place process to identify and correct all sources of
excessive IOD. It is now safe to select the lowest mil-
liampere scale of the multi-meter to check the low-
amperage IOD.
CAUTION: Do not open any doors, or turn on any
electrical accessories with the lowest milliampere
scale selected, or the multi-meter may be damaged.
(6) Observe the multi-meter reading. The low-am-
perage IOD should not exceed thirty-five milliam-
peres (0.035 ampere). If the current draw exceeds
thirty-five milliamperes, isolate each circuit using the
fuse and circuit breaker remove-and-replace processin Step 5. The multi-meter reading will drop to
within the acceptable limit when the source of the
excessive current draw is disconnected. Repair this
circuit as required; whether a wiring short, incorrect
switch adjustment, or a component failure is at fault.
STANDARD PROCEDURE - USING
MIDTRONICS ELECTRICAL TESTER
Always use the Midtronics Instruction Manual that
was supplied with the tester as a reference. If the
Instruction Manual is not available the following pro-
cedure can be used:
WARNING: ALWAYS WEAR APPROPRIATE EYE
PROTECTION AND USE EXTREME CAUTION WHEN
WORKING WITH BATTERIES.
BATTERY TESTING
(1) If testing the battery OUT-OF-VEHICLE, clean
the battery terminals with a wire brush before test-
ing. If the battery is equipped with side post termi-
nals, install and tighten the supplied lead terminal
stud adapters. Do not use steel bolts. Failure to prop-
erly install the stud adapters, or using stud adapters
that are dirty or worn-out may result in false test
readings.
(2) If testing the battery IN-THE-VEHICLE, make
certain all of the vehicle accessory loads are OFF,
including the ignition.The preferred test position
is at the battery terminal. If the battery is not
accessible, you may test using both the positive and
Fig. 15 MIDTRONICS BATTERY AND CHARGING
SYSTEM TESTER - Micro420
KJBATTERY SYSTEM 8F - 15
BATTERY (Continued)

(2) Reinstall the battery thermal guard onto the
battery case. Refer to Thermal Guard for the proper
battery thermal guard installation procedures.
(3) Position the battery and the battery thermal
guard onto the battery tray as a unit. Ensure that
the battery positive and negative terminal posts are
correctly positioned. The battery cable terminal
clamps must reach the correct battery terminal post
without stretching the cables (Fig. 17).
(4) Reinstall the battery holddowns onto the bat-
tery. Refer to Battery Holddown for the proper instal-
lation procedure.
CAUTION: Be certain that the battery cable terminal
clamps are connected to the correct battery termi-
nal posts. Reversed battery polarity may damage
electrical components of the vehicle.
(5) Clean the battery cable terminal clamps and
the battery terminal posts. Refer to Battery System
Cleaning for cleaning procedure.
(6) Reconnect the battery positive cable terminal
clamp to the battery positive terminal post. Tighten
the terminal clamp pinch-bolt hex nut to 45 in. lbs.
(7) Reconnect the battery negative cable terminal
clamp to the battery negative terminal post. Tighten
the terminal clamp pinch-bolt hex nut to 45 in. lbs.
(8) Apply a thin coating of petroleum jelly or chas-
sis grease to the exposed surfaces of the battery cable
terminal clamps and the battery terminal posts.BATTERY HOLDDOWN
DESCRIPTION
The battery holddown hardware includes a plastic
holddown bracket and retaining bolt. The battery
holddown bracket meshes with the battery tray to
secure the battery to the battery tray.
When installing a battery into the battery tray, it
is important that the holddown hardware is properly
installed and that the fastener is tightened to the
proper specifications. Improper holddown fastener
tightness, whether too loose or too tight, can result in
damage to the battery, the vehicle, or both. Refer to
Battery Holddown for the proper installation proce-
dure, including the proper holddown fastener torque
specifications.
OPERATION
The battery holddown secures the battery in the
battery tray. This holddown is designed to prevent
battery movement during the most extreme vehicle
operation conditions. Periodic removal and lubrica-
tion of the battery holddown hardware is recom-
mended to prevent hardware seizure at a later date.
CAUTION: Never operate a vehicle without a battery
holddown device properly installed. Damage to the
vehicle, components and battery could result.
REMOVAL
(1) Turn the ignition switch to the Off position. Be
certain that all electrical accessories are turned off.
(2) Loosen the battery negative cable terminal
clamp pinch-bolt hex nut.
(3) Disconnect the battery negative cable terminal
clamp from the battery negative terminal post. If
necessary, use a battery terminal puller to remove
the terminal clamp from the battery post.
(4) Remove the battery hold down bracket retain-
ing bolt from the threaded insert in the battery tray
assembly.
INSTALLATION
(1) Clean and inspect the battery hold down hard-
ware. Refer to Battery Cleaning for the proper bat-
tery system component cleaning procedures, and
Battery Inspection for the proper battery system
component inspection procedures.
(2) Position the battery hold down bracket onto the
battery tray.
Fig. 17 Battery Cables - Typical
1 - RADIATOR CROSSMEMBER
2 - WHEELHOUSE INNER PANEL
3 - NEGATIVE CABLE
4 - POSITIVE CABLE
5 - BATTERY
KJBATTERY SYSTEM 8F - 17
BATTERY (Continued)

(3) Install and tighten the battery hold down
bracket retaining bolt. Tighten the bolt to 4 N´m (20
in. lbs.).
(4) Reconnect the battery negative cable terminal
clamp to the battery negative terminal post. Tighten
the terminal clamp pinch-bolt hex nut to 8.4 N´m (75
in. lbs.).
BATTERY CABLES
DESCRIPTION
The battery cables (Fig. 18) are large gauge,
stranded copper wires sheathed within a heavy plas-
tic or synthetic rubber insulating jacket. The wire
used in the battery cables combines excellent flexibil-
ity and reliability with high electrical current carry-
ing capacity. The battery cables feature a clamping
type female battery terminal made of soft lead that is
die cast onto one end of the battery cable wire. A
square headed pinch-bolt and hex nut are installed
at the open end of the female battery terminal clamp.
Large eyelet type terminals are crimped onto the
opposite end of the battery cable wire and then sol-
der-dipped. The battery positive cable wires have a
red insulating jacket to provide visual identificationand feature a larger female battery terminal clamp
to allow connection to the larger battery positive ter-
minal post. The battery negative cable wires have a
black insulating jacket and a smaller female battery
terminal clamp.
The battery cables cannot be repaired and, if dam-
aged or faulty they must be replaced. Both the bat-
tery positive and negative cables are available for
service replacement only as a unit with the battery
wire harness, which may include portions of the wir-
ing circuits for the generator and other components
on some models. Refer to the appropriate wiring
information in this service manual for the location of
the proper battery cable wire harness diagrams. The
wiring information also includes proper wire and con-
nector repair procedures, further details on wire har-
ness routing and retention, as well as pin-out and
location views for the various wire harness connec-
tors, splices and grounds.
OPERATION
The battery cables connect the battery terminal
posts to the vehicle electrical system. These cables
also provide a path back to the battery for electrical
current generated by the charging system for restor-
ing the voltage potential of the battery. The female
battery terminal clamps on the ends of the battery
cable wires provide a strong and reliable connection
of the battery cable to the battery terminal posts.
The terminal pinch bolts allow the female terminal
clamps to be tightened around the male terminal
posts on the top of the battery. The eyelet terminals
secured to the opposite ends of the battery cable
wires from the female battery terminal clamps pro-
vide secure and reliable connection of the battery
cables to the vehicle electrical system.
The battery positive cable terminal clamp is die
cast onto the ends of two wires. One wire has an eye-
let terminal that connects the battery positive cable
to the B(+) terminal studs of the Power Distribution
Center (PDC), and the other wire has an eyelet ter-
minal that connects the battery positive cable to the
B(+) terminal stud of the engine starter motor sole-
noid. The battery negative cable terminal clamp is
also die cast onto the ends of two wires. One wire
has an eyelet terminal that connects the battery neg-
ative cable to the vehicle powertrain through a stud
on the left side of the engine cylinder block. The
other wire has an eyelet terminal that connects the
battery negative cable to the vehicle body through a
ground stud on the left wheel house, near the bat-
tery.
Fig. 18 Battery Cables - Typical
1 - Battery
2 - Radiator Crossmember
3 - Terminal Clamps
4 - Fender Inner Shield
5 - Negative Cable
6 - Positive Cable
8F - 18 BATTERY SYSTEMKJ
BATTERY HOLDDOWN (Continued)

(2) Carefully and evenly slide the battery thermal
guard down over the battery case.
(3) Install the battery and the battery thermal
guard into the battery tray as a unit. Refer to Bat-
tery Installation for the proper battery installation
procedures.
BATTERY TRAY
DESCRIPTION
The battery is placed in a molded plastic tray
located in the left front corner of the engine compart-
ment (Fig. 25). The battery hold down hardware is
contained within the battery tray. A hole in the bot-
tom of the battery tray is fitted with a battery tem-
perature sensor. Refer to Charging System for more
information on the battery temperature sensor. Refer
to Battery Hold down for more information on hold
down hardware.
OPERATION
The battery tray provides a secure mounting loca-
tion and supports the battery. On some vehicles, the
battery tray also provides the anchor point/s for the
battery holddown hardware. The battery tray and
the battery holddown hardware combine to secure
and stabilize the battery in the engine compartment,
which prevents battery movement during vehicle
operation. Unrestrained battery movement during
vehicle operation could result in damage to the vehi-
cle, the battery, or both.
REMOVAL
(1) Remove the battery from the battery tray
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - REMOVAL).
(2) Unlatch and remove the PDC from the battery
tray.
(3) Remove the battery temperature sensor from
the battery tray (Refer to 8 - ELECTRICAL/CHARG-
ING/BATTERY TEMPERATURE SENSOR -
REMOVAL).
(4) Remove the three nuts that secure the battery
tray to the weld studs on the front extension of the
left front wheelhouse inner panel (Fig. 25).
(5) Remove the battery tray from the vehicle.
INSTALLATION
(1) Clean and inspect the battery tray (Refer to 8 -
ELECTRICAL/BATTERY SYSTEM - CLEANING).
(2) Position the battery tray onto the weld studs
on the front extension of the left front wheelhouse
inner panel.
(3) Install the battery temperature sensor onto the
battery tray (Refer to 8 - ELECTRICAL/CHARGING/
BATTERY TEMPERATURE SENSOR - INSTALLA-
TION).
(4) Install and tighten the three nuts that secure
the battery tray to the weld studs on the front exten-
sion of the left front wheelhouse inner panel. Tighten
the nuts to 5 N´m (45 in. lbs.).
(5) Install the PDC on the battery tray.
(6) Install the battery onto the battery tray (Refer
to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY -
INSTALLATION).
Fig. 24 Battery thermal guard
1 - THERMAL GUARD
2 - BATTERY
Fig. 25 Battery Tray Location
1 - Battery Tray
2 - Battery Tray Retaining Nuts
KJBATTERY SYSTEM 8F - 21
THERMAL GUARD (Continued)

STARTER MOTOR - GAS POWERED
Starter Motor and Solenoid
Manufacturer Mitsubishi
Engine Application 2.4L / 3.7L
Power Rating 1.4 Kilowatt (1.9 Horsepower)
Voltage12 Volts
** Number of Permanent Magnets 6
Number of Brushes 4
Drive Type Planetary Gear Reduction
Free Running Test Voltage 11.2 Volts
Free Running Test Maximum Amperage Draw 90 Amperes
Free Running Test Minimum Speed 2400 rpm
Solenoid Closing Maximum Voltage Required 7.8 Volts
* Cranking Amperage Draw Test 160 Amperes
*Test at operating temperature. Cold engine, tight (new) engine, or heavy oil will increase starter amperage draw.
**The starter is equipped with permanent magnets. Never strike the starter case to attempt to loosen a sticking/
stuck armature as permanent magnets may crack or break.
STARTER MOTOR
DIAGNOSIS AND TESTING - STARTER MOTOR
Correct starter motor operation can be confirmed
by performing the following free running bench test.
This test can only be performed with starter motor
removed from vehicle. Refer to Specifications for
starter motor specifications.
(1) Remove starter motor from vehicle. Refer to
Starter Motor Removal and Installation.
(2) Mount starter motor securely in a soft-jawed
bench vise. The vise jaws should be clamped on the
mounting flange of starter motor. Never clamp on
starter motor by field frame.
(3) Connect a suitable volt-ampere tester and a
12-volt battery to starter motor in series, and set
ammeter to 100 ampere scale. See instructions pro-
vided by manufacturer of volt-ampere tester being
used.
(4) Install jumper wire from solenoid terminal to
solenoid battery terminal. The starter motor should
operate. If starter motor fails to operate, replace
faulty starter motor assembly.
(5) Adjust carbon pile load of tester to obtain free
running test voltage. Refer to Specifications for
starter motor free running test voltage specifications.
(6) Note reading on ammeter and compare reading
to free running test maximum amperage draw. Refer
to Specifications for starter motor free running test
maximum amperage draw specifications.(7) If ammeter reading exceeds maximum amper-
age draw specification, replace faulty starter motor
assembly.
STARTER SOLENOID
This test can only be performed with starter motor
removed from vehicle.
(1) Remove starter motor from vehicle. Refer to
Starter Motor Removal and Installation.
(2) Disconnect wire from solenoid field coil termi-
nal.
(3) Check for continuity between solenoid terminal
and solenoid field coil terminal with a continuity
tester (Fig. 7). There should be continuity. If OK, go
to Step 4. If not OK, replace faulty starter motor
assembly.
(4) Check for continuity between solenoid terminal
and solenoid case (Fig. 8). There should be continuity.
If not OK, replace faulty starter motor assembly.
REMOVAL
2.4L 4±Cylinder
(1) Disconnect and isolate negative battery cable.
(2) Raise and support vehicle.
(3) Remove solenoid wire from solenoid terminal
(Fig. 11).
(4) Remove battery cable from stud on starter sole-
noid (Fig. 11).
(5) Remove 2 starter mounting bolts (Fig. 9) and
remove starter from vehicle.
KJSTARTING SYSTEM 8F - 39
STARTING SYSTEM (Continued)