2002 JEEP LIBERTY Workshop Manual

controls the ground for the heated seat switch indi-
cator lamps (LED's).
When a heated seat switch (Driver or Passenger) is
depressed a signal is received by the heated seat
module, the module energizes the proper indicator
LED (Low or High) in the switch by grounding the
indicator lamp circuit to indicate that the heated seat
system is operating. At the same time, the heated
seat module energizes the selected heated seat sensor
circuit and the sensor provides the module with an
input indicating the surface temperature of the
selected seat cushion.
The Low heat set point is about 36É C (96.8É F),
and the High heat set point is about 42É C (107.6É F).
If the seat cushion surface temperature input is
below the temperature set point for the selected tem-
perature setting, the heated seat module energizes
an N-channel Field Effect Transistor (N-FET) within
the module which energizes the heated seat elements
in the selected seat cushion and back. When the sen-
sor input to the module indicates the correct temper-
ature set point has been achieved, the module
de-energizes the N-FET which de-energizes the
heated seat elements. The heated seat module will
continue to cycle the N-FET as needed to maintain
the selected temperature set point.
If the heated seat module detects a heated seat
sensor value input that is out of range or a shorted
or open heated seat element circuit, it will notify the
vehicle operator or the repair technician of this con-
dition by flashing the High and/or Low indicator
lamps in the affected heated seat switch. Refer to
Diagnosis and Testing Heated Seat Systemin
Heated Systems for flashing LED diagnosis and test-
ing procedures. Refer toDiagnosis and Testing
Heated Seat Modulein this section for heated seat
module diagnosis and testing procedures. Also refer
to the Body Diagnostic Manual for additional diagno-
sis and testing procedures.
DIAGNOSIS AND TESTING - HEATED SEAT
MODULE
If a heated seat fails to heat and one or both of the
indicator lamps on a heated seat switch flash, refer
toHeated Seat System Diagnosis and Testingin
Heated Systems for flashing LED failure identifica-
tion. Refer toWiring Diagramsin for complete
heated seat system wiring diagrams.
(1) Remove the heated seat module from its
mounting location (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/MEMORY HEATED
SEAT/MIRROR MODULE - REMOVAL).NOTE: ANY RESISTANCE VALUES (OHMSV) GIVEN
IN THE FOLLOWING TEXT ARE SUPPLIED USING
THE AUTOMATIC RANGE GENERATED BY A
FLUKETAUTOMOTIVE METER. IF ANOTHER TYPE
OF MEASURING DEVICE IS USED THE VALUES
GENERATED MAY NOT BE THE SAME AS THE
RESULTS SHOWN HERE, OR MAY HAVE TO BE
CONVERTED TO THE RANGE USED HERE.
RIGHT SEAT HEATER INOPERATIVE
(1) If a heated seat heats but one or both indicator
lamps (LED's) on the heated seat switch fail to illu-
minate, check the driver circuit with the inoperative
LED for a short to ground. If OK, replace the heated
seat switch. If NOT OK repair the short to ground as
required and than replace the heated seat switch.
NOTE: IF THE RIGHT SEAT CUSHION IS ALREADY
WARM THE FOLLOWING STEP WILL NOT PROVE
CONCLUSIVE.
(2) Back-probe the heated seat module wire har-
ness connector (Fig. 15), do not disconnect. Check
cavity #3 for battery voltage when the right heated
seat switch is turned ªONº, voltage should be
present, If OK go to Step 3 If NOT OK, test the right
heated seat switch (Refer to 8 - ELECTRICAL/
HEATED SEATS/PASSENGER HEATED SEAT
SWITCH - DIAGNOSIS AND TESTING). If the
switch tests OK, check for continuity between the
switch and control module on the MUX circuit, If OK
replace the heated seat control module. If NOT OK,
repair the open or shorted MUX circuit as required.
Fig. 15 Heated Seat Module Electrical Connector
8E - 22 ELECTRONIC CONTROL MODULESKJ
HEATED SEAT MODULE (Continued)

NOTE: BE CERTAIN THE BATTERY IS FULLY
CHARGED BEFORE TESTING. FAILURE TO DO SO
CAN RESULT IN INCORRECT READINGS.
(3) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #10
for battery voltage, while observing the voltmeter
depress the right heated seat switchlowsetting
twice, voltage should toggle between approx.12v and
8v, If OK go to Step 4. If NOT OK check for continu-
ity between the switch and control module on the low
heat driver circuit, If OK replace the heated seat con-
trol module.
(4) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #11
for battery voltage, while observing the voltmeter
depress the right heated seat switchhighsetting
twice, voltage should toggle between approx.12v and
8v, If OK go to Step 5. If NOT OK check for continu-
ity between the switch and control module on the
high heat driver circuit, If OK replace the heated
seat control module.
(5) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #2 for
approx. 5v, voltage should be present, If OK go to
Step 6. If NOT OK replace the heated seat control
module.
(6) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #7 for
a range in voltage from 1.72v (warm seat) ± 3.0v
(cold seat). It should be within this range, If OK
replace the heated seat module. If NOT OK test the
Heated Seat Sensor. If NOT OK, replace the right
heated seat element and sensor assembly. If the
heated seat sensor tests OK, check for continuity
between the right heated seat cushion connector and
control module connector on the 5v supply circuit, If
NOT OK, repair the open or shorted 5v supply circuit
as required. If OK check for continuity between the
right heated seat cushion connector and control mod-
ule connector on the temperature sensor input cir-
cuit. If NOT OK, repair the open or shorted
temperature sensor input circuit as required. If OK
replace the heated seat control module.
LEFT SEAT HEATER INOPERATIVE
(1) If a heated seat heats but one or both indicator
lamps (LED's) on the heated seat switch fail to illu-
minate, check the driver circuit with the inoperative
LED for a short to ground. If OK, replace the heated
seat switch. If NOT OK repair the short to ground as
required and than replace the heated seat switch.
NOTE: IF THE LEFT SEAT CUSHION IS ALREADY
WARM THE FOLLOWING STEP WILL NOT PROVE
CONCLUSIVE.(2) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #5 for
battery voltage when the left heated seat switch is
turned ªONº, voltage should be present, If OK go to
Step 3 If NOT OK, test the left heated seat switch
(Refer to 8 - ELECTRICAL/HEATED SEATS/
DRIVER HEATED SEAT SWITCH - DIAGNOSIS
AND TESTING). If the switch tests OK, check for
continuity between the switch and control module on
the MUX circuit, If OK replace the heated seat con-
trol module. If NOT OK, repair the open or shorted
MUX circuit as required.
(3) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #12
for battery voltage, while observing the voltmeter
depress the left heated seat switchlowsetting twice,
voltage should toggle between approx.12v and 8v, If
OK go to Step 4. If NOT OK check for continuity
between the switch and control module on the low
heat driver circuit, If OK replace the heated seat con-
trol module.
(4) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #14
for battery voltage, while observing the voltmeter
depress the left heated seat switchhighsetting
twice, voltage should toggle between approx.12v and
8v, If OK go to Step 5. If NOT OK check for continu-
ity between the switch and control module on the
high heat driver circuit, If OK replace the heated
seat control module.
(5) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #2 for
approx. 5v, 5 voltage should be present, If OK go to
Step 6. If NOT OK replace the heated seat control
module.
(6) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #8 for
a range in voltage from 1.72v (warm seat) ± 3.0v
(cold seat). It should be within this range, If OK
replace the heated seat control module. If NOT OK,
test the Heated Seat Sensor. If NOT OK, replace the
left heated seat element and sensor assembly. If the
heated seat sensor tests OK, check for continuity
between the left heated seat cushion connector and
control module connector on the 5v supply circuit, If
NOT OK, repair the open or shorted 5v supply circuit
as required. If OK check for continuity between the
left heated seat cushion connector and control mod-
ule connector on the temperature sensor input cir-
cuit. If NOT OK, repair the open or shorted
temperature sensor input circuit as required. If OK
replace the heated seat control module.
KJELECTRONIC CONTROL MODULES 8E - 23
HEATED SEAT MODULE (Continued)

BOTH SEATS INOPERATIVE
If both seats (driver and passenger) fail to heat
and the indicator lamps on the heated seat switches
for both seats fail to operate, test the heated seat
fuses in the junction block. If the heated seat fuses
check OK, go to Step 1.
(1) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check for continu-
ity between the ground circuit cavity #13 of the
heated seat module connector and a good ground. If
OK go to Step 2. If NOT OK, repair the open or
shorted ground circuit as required.
(2) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #4
and #6 for battery voltage, voltage should be present,
If OK go to Step 3. If NOT OK repair the open or
shorted fused B(+) circuit as required.
(3) Back-probe the heated seat module wire har-
ness connector, do not disconnect. Check cavity #2 for
approx. 5v, voltage should be present, replace the
heated seat control module with a known good mod-
ule and verify system operation.
REMOVAL
(1) Working under the front seat cushion (Fig. 16),
remove the heated seat module from its mounting
bracket by gently prying the module off of the two
mounting pushpins.
(2) Disconnect the seat wire harness connector
from the connector receptacle on the side of the
heated seat module.
(3) Remove the heated seat module from the vehi-
cle.
INSTALLATION
(1) Connect the seat wire harness connector to the
connector receptacle on the side of the heated seat
module.
(2) Install the heated seat module on its mounting
bracket under the front seat.
(3) Verify heated seat system operation.
Fig. 16 Heated Seat Module Location
1 - Front Seat Cushion
2 - Heated Seat Module
3 - Electrical Connector
8E - 24 ELECTRONIC CONTROL MODULESKJ
HEATED SEAT MODULE (Continued)

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)

BATTERY SYSTEM DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
THE BATTERY SEEMS WEAK OR
DEAD WHEN ATTEMPTING TO
START THE ENGINE.1. The electrical system ignition-off
draw is excessive.1. Refer to the IGNITION-OFF
DRAW TEST Standard Procedure
for the proper test procedures.
Repair the excessive ignition-off
draw, as required.
2. The charging system is faulty. 2. Determine if the charging system
is performing to specifications using
the Midtronics battery and charging
system tester. Refer to Charging
System for additional charging
system diagnosis and testing
procedures. Repair the faulty
charging system, as required.
3. The battery is discharged. 3. Determine the battery state-of-
charge using the Midtronics battery
and charging system tester. Refer to
the Standard Procedures in this
section for additional test
procedures. Charge the faulty
battery, as required.
4. The battery terminal connections
are loose or corroded.4. Refer to Battery Cables for the
proper battery cable diagnosis and
testing procedures. Clean and
tighten the battery terminal
connections, as required.
5. The battery has an incorrect size
or rating for this vehicle.5. Refer to Battery System
Specifications for the proper size
and rating. Replace an incorrect
battery, as required.
6. The battery is faulty. 6. Determine the battery cranking
capacity using the Midtronics battery
and charging system tester. Refer to
the Standard Procedures in this
section for additional test
procedures. Replace the faulty
battery, as required.
7. The starting system is faulty. 7. Determine if the starting system
is performing to specifications. Refer
to Starting System for the proper
starting system diagnosis and
testing procedures. Repair the faulty
starting system, as required.
8. The battery is physically
damaged.8. Inspect the battery for loose
terminal posts or a cracked and
leaking case. Replace the damaged
battery, as required.
KJBATTERY SYSTEM 8F - 3
BATTERY SYSTEM (Continued)

BATTERY SYSTEM DIAGNOSIS
CONDITION POSSIBLE CAUSES CORRECTION
THE BATTERY STATE OF
CHARGE CANNOT BE
MAINTAINED.1. The battery has an incorrect size
or rating for this vehicle.1. Refer to Battery System
Specifications for the proper
specifications. Replace an incorrect
battery, as required.
2. The battery terminal connections
are loose or corroded.2. Refer to Battery Cable for the
proper cable diagnosis and testing
procedures. Clean and tighten the
battery terminal connections, as
required.
3. The electrical system ignition-off
draw is excessive.3. Refer to the IGNITION-OFF
DRAW TEST Standard Procedure
for the proper test procedures.
Repair the faulty electrical system,
as required.
4. The battery is faulty. 4. Test the battery using the
Midtronics battery and charging
system tester. Refer to Standard
Procedures for additional test
procedures. Replace the faulty
battery, as required.
5. The starting system is faulty. 5. Determine if the starting system
is performing to specifications. Refer
to Starting System for the proper
starting system diagnosis and
testing procedures. Repair the faulty
starting system, as required.
6. The charging system is faulty. 6. Determine if the charging system
is performing to specifications using
the Midtronics battery and charging
system tester.. Refer to Charging
System for additional charging
system diagnosis and testing
procedures. Repair the faulty
charging system, as required.
7. Electrical loads exceed the
output of the charging system.7. Inspect the vehicle for
aftermarket electrical equipment
which might cause excessive
electrical loads.
8. Slow driving or prolonged idling
with high-amperage draw systems
in use.8. Advise the vehicle operator, as
required.
THE BATTERY WILL NOT ACCEPT
A CHARGE.1. The battery is faulty. 1. Test the battery using the
Midtronics battery and charging
system tester.. Charge or replace
the faulty battery, as required.
8F - 4 BATTERY SYSTEMKJ
BATTERY SYSTEM (Continued)

ABNORMAL BATTERY DISCHARGING
Any of the following conditions can result in abnor-
mal battery discharging:
²A faulty or incorrect charging system compo-
nent. Refer to Charging System for the proper charg-
ing system diagnosis and testing procedures.
²A faulty or incorrect battery. Refer to Standard
Procedures for the proper battery diagnosis and test-
ing procedures. Refer to Battery System Specifica-
tions for the proper specifications.
²A faulty circuit or component causing excessive
ignition-off draw.
²Electrical loads that exceed the output of the
charging system. This can be due to equipment
installed after manufacture, or repeated short trip
use.
²A faulty or incorrect starting system component.
Refer to Starting System for the proper starting sys-
tem diagnosis and testing procedures.
²Corroded or loose battery posts and terminal
clamps.
²A loose or worn generator drive belt.
²Slow driving speeds (heavy traffic conditions) or
prolonged idling, with high-amperage draw systems
in use.
CLEANING
The following information details the recommended
cleaning procedures for the battery and related com-
ponents. In addition to the maintenance schedules
found in this service manual and the owner's man-
ual, it is recommended that these procedures be per-
formed any time the battery or related components
must be removed for vehicle service.
(1) Clean the battery cable terminal clamps of all
corrosion. Remove any corrosion using a wire brush
or a post and terminal cleaning tool, and a sodium
bicarbonate (baking soda) and warm water cleaning
solution (Fig. 1).
(2) Clean the battery tray and battery holddown
hardware of all corrosion. Remove any corrosion
using a wire brush and a sodium bicarbonate (baking
soda) and warm water cleaning solution. Paint any
exposed bare metal.
(3) If the removed battery is to be reinstalled,
clean the outside of the battery case and the top
cover with a sodium bicarbonate (baking soda) and
warm water cleaning solution using a stiff bristle
parts cleaning brush to remove any acid film (Fig. 2).
Rinse the battery with clean water. Ensure that the
cleaning solution does not enter the battery cells
through the vent holes. If the battery is being
replaced, refer to Battery System Specifications for
the factory-installed battery specifications. Confirm
that the replacement battery is the correct size and
has the correct ratings for the vehicle.
Fig. 1 Clean Battery Cable Terminal Clamp - Typical
1 - TERMINAL BRUSH
2 - BATTERY CABLE
Fig. 2 Clean Battery - Typical
1 - CLEANING BRUSH
2 - WARM WATER AND BAKING SODA SOLUTION
3 - BATTERY
KJBATTERY SYSTEM 8F - 5
BATTERY SYSTEM (Continued)