2002 JEEP LIBERTY ignition

²Transmission convertor clutch circuit. Driven
through J1850 circuits.
OPERATION - 5 VOLT SUPPLIES
Primary 5±volt supply:
²supplies the required 5 volt power source to the
Crankshaft Position (CKP) sensor.
²supplies the required 5 volt power source to the
Camshaft Position (CMP) sensor.
²supplies a reference voltage for the Manifold
Absolute Pressure (MAP) sensor.
²supplies a reference voltage for the Throttle
Position Sensor (TPS) sensor.
Secondary 5±volt supply:
²supplies the required 5 volt power source to the
oil pressure sensor.
²supplies the required 5 volt power source for the
Vehicle Speed Sensor (VSS) (if equipped).
²supplies the 5 volt power source to the transmis-
sion pressure sensor (certain automatic transmis-
sions).
OPERATION - IGNITION CIRCUIT SENSE
The ignition circuit sense input tells the PCM the
ignition switch has energized the ignition circuit.
Battery voltage is also supplied to the PCM
through the ignition switch when the ignition is in
the RUN or START position. This is referred to as
the9ignition sense9circuit and is used to9wake up9
the PCM. Voltage on the ignition input can be as low
as 6 volts and the PCM will still function. Voltage is
supplied to this circuit to power the PCM's 8-volt reg-
ulator and to allow the PCM to perform fuel, ignition
and emissions control functions.
REMOVAL
USE THE DRB SCAN TOOL TO REPROGRAM
THE NEW POWERTRAIN CONTROL MODULE
(PCM) WITH THE VEHICLES ORIGINAL IDEN-
TIFICATION NUMBER (VIN) AND THE VEHI-
CLES ORIGINAL MILEAGE. IF THIS STEP IS
NOT DONE, A DIAGNOSTIC TROUBLE CODE
(DTC) MAY BE SET.
The PCM is located in the engine compartment
near the battery (Fig. 9).
To avoid possible voltage spike damage to the
PCM, ignition key must be off, and negative battery
cable must be disconnected before unplugging PCM
connectors.
(1) Disconnect negative battery cable at battery.
(2) Remove cover over electrical connectors. Cover
snaps onto PCM.
(3) Carefully unplug the three 32±way connectors
from PCM.
(4) Remove three PCM mounting bolts and remove
PCM from vehicle.
INSTALLATION
USE THE DRB SCAN TOOL TO REPROGRAM
THE NEW POWERTRAIN CONTROL MODULE
(PCM) WITH THE VEHICLES ORIGINAL IDEN-
TIFICATION NUMBER (VIN) AND THE VEHI-
CLES ORIGINAL MILEAGE. IF THIS STEP IS
NOT DONE, A DIAGNOSTIC TROUBLE CODE
(DTC) MAY BE SET.
(1) Install PCM and 3 mounting bolts to vehicle.
(2) Tighten bolts. Refer to torque specifications.
(3) Check pin connectors in the PCM and the three
32±way connectors for corrosion or damage. Also, the
pin heights in connectors should all be same. Repair
as necessary before installing connectors.
(4) Install three 32±way connectors.
(5) Install cover over electrical connectors. Cover
snaps onto PCM.
(6) Install battery cable.
(7) Use the DRB scan tool to reprogram new PCM
with vehicles original Identification Number (VIN)
and original vehicle mileage.
SENTRY KEY IMMOBILIZER
MODULE
DESCRIPTION
The Sentry Key Immobilizer Module (SKIM) is the
primary component of the Sentry Key Immobilizer
System (SKIS) (Fig. 10). The SKIM is located on the
right side of the steering column, below the ignition
Fig. 9 PCM REMOVE/INSTALL
1 - PCM
2 - MOUNTING BOLTS (3)
3 - 32-WAY CONNECTORS
KJELECTRONIC CONTROL MODULES 8E - 15
POWERTRAIN CONTROL MODULE (Continued)

lock cylinder housing and is concealed beneath the
steering column shrouds. The molded black plastic
housing for the SKIM has an integral molded plastic
halo-like antenna ring that extends from one end.
When the SKIM is properly installed on the steering
column, the antenna ring is oriented around the cir-
cumference of the ignition lock cylinder housing. A
single integral connector receptacle containing six
terminal pins is located on the opposite end of the
SKIM housing from the antenna ring. A stamped
metal mounting bracket secured to the SKIM hous-
ing has a U-shaped clip formation that is used to
secure the unit to the right lower flange of the steer-
ing column jacket.
The SKIM cannot be adjusted or repaired. If faulty
or damaged, the entire SKIM unit must be replaced.
OPERATION
The Sentry Key Immobilizer Module (SKIM) con-
tains a Radio Frequency (RF) transceiver and a
microprocessor. The SKIM transmits RF signals to,
and receives RF signals from the Sentry Key tran-
sponder through a tuned antenna enclosed within the
molded plastic antenna ring integral to the SKIM
housing. If this antenna ring is not mounted properly
around the ignition lock cylinder housing, communi-
cation problems between the SKIM and the transpon-
der may arise. These communication problems will
result in Sentry Key transponder-related faults. The
SKIM also communicates over the Programmable
Communications Interface (PCI) data bus with the
Powertrain Control Module (PCM), the ElectroMe-
chanical Instrument Cluster (EMIC) and/or the
DRBIIItscan tool.The SKIM retains in memory the ID numbers of
any Sentry Key transponder that is programmed into
it. A maximum of eight Sentry Key transponders can
be programmed into the SKIM. For added system
security, each SKIM is programmed with a unique
Secret Key code. This code is stored in memory, sent
over the PCI data bus to the PCM, and is encoded to
the transponder of every Sentry Key that is pro-
grammed into the SKIM. Therefore, the Secret Key
code is a common element that is found in every com-
ponent of the Sentry Key Immobilizer System (SKIS).
Another security code, called a PIN, is used to gain
access to the SKIM Secured Access Mode. The
Secured Access Mode is required during service to
perform the SKIS initialization and Sentry Key tran-
sponder programming procedures. The SKIM also
stores the Vehicle Identification Number (VIN) in its
memory, which it learns through a PCI data bus
message from the PCM during SKIS initialization.
In the event that a SKIM replacement is required,
the Secret Key code can be transferred to the new
SKIM from the PCM using the DRBIIItscan tool
and the SKIS initialization procedure. Proper com-
pletion of the SKIS initialization will allow the exist-
ing Sentry Keys to be programmed into the new
SKIM so that new keys will not be required. In the
event that the original Secret Key code cannot be
recovered, SKIM replacement will also require new
Sentry Keys. The DRBIIItscan tool will alert the
technician during the SKIS initialization procedure if
new Sentry Keys are required.
When the ignition switch is turned to the On posi-
tion, the SKIM transmits an RF signal to the tran-
sponder in the ignition key. The SKIM then waits for
an RF signal response from the transponder. If the
response received identifies the key as valid, the
SKIM sends a valid key message to the PCM over
the PCI data bus. If the response received identifies
the key as invalid, or if no response is received from
the key transponder, the SKIM sends an invalid key
message to the PCM. The PCM will enable or disable
engine operation based upon the status of the SKIM
messages. It is important to note that the default
condition in the PCM is an invalid key; therefore, if
no message is received from the SKIM by the PCM,
the engine will be disabled and the vehicle immobi-
lized after two seconds of running.
The SKIM also sends SKIS indicator status mes-
sages to the EMIC over the PCI data bus to tell the
EMIC how to operate the SKIS indicator. This indi-
cator status message tells the EMIC to turn the indi-
cator on for about three seconds each time the
ignition switch is turned to the On position as a bulb
test. After completion of the bulb test, the SKIM
sends indicator status messages to the EMIC to turn
the indicator off, turn the indicator on, or to flash the
Fig. 10 Sentry Key Immobilizer Module
1 - SKIM
2 - BRACKET
3 - CONNECTOR RECEPTACLE
4 - ANTENNA RING
8E - 16 ELECTRONIC CONTROL MODULESKJ
SENTRY KEY IMMOBILIZER MODULE (Continued)

indicator on and off. If the SKIS indicator flashes
upon ignition On or stays on solid after the bulb test,
it signifies a SKIS fault. If the SKIM detects a sys-
tem malfunction and/or the SKIS has become inoper-
ative, the SKIS indicator will stay on solid. If the
SKIM detects an invalid key or if a key transponder-
related fault exists, the SKIS indicator will flash. If
the vehicle is equipped with the Customer Learn
transponder programming feature, the SKIM will
also send messages to the EMIC to flash the SKIS
indicator and to generate a single audible chime tone
whenever the Customer Learn programming mode is
being utilized. (Refer to 8 - ELECTRICAL/VEHICLE
THEFT SECURITY - STANDARD PROCEDURE -
SENTRY KEY TRANSPONDER PROGRAMMING).
The SKIS performs a self-test each time the igni-
tion switch is turned to the On position, and will
store fault information in the form of Diagnostic
Trouble Codes (DTC's) in SKIM memory if a system
malfunction is detected. The SKIM can be diagnosed,
and any stored DTC's can be retrieved using a
DRBIIItscan tool. Refer to the appropriate diagnos-
tic information.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Disconnect and isolate the battery negative
cable.
(2) If the vehicle is equipped with the optional tilt
steering column, move the tilt steering column to the
fully lowered position and leave the tilt release lever
in the released (down) position.
(3) From below the steering column, remove the
two screws that secure the lower shroud to the upper
shroud (Fig. 11).
(4) Using hand pressure, push gently inward on
both sides of the upper shroud near the parting line
between the upper and lower shrouds to release thesnap features that secure the two halves to each
other.
(5) Remove both the upper and lower shrouds from
the steering column.
(6) Disconnect the instrument panel wire harness
connector for the SKIM from the module connector
receptacle.
(7) The SKIM mounting bracket features a clip for-
mation that secures the SKIM to the right lower
flange of the steering column jacket. Pull downward
on the connector end of the SKIM mounting bracket
to release this clip from the steering column jacket.
(8) Rotate the SKIM and its mounting bracket
downwards and then to the side away from the steer-
ing column to slide the SKIM antenna ring from
around the ignition switch lock cylinder housing. Lift
the multi-function switch upward off of the upper
steering column housing far enough to remove the
SKIM antenna ring formation from between the igni-
tion key release button and the multi-function switch
housing.
(9) Remove the SKIM from the steering column.
Fig. 11 Sentry Key Immobilizer Module Remove/
Install
1 - UPPER SHROUD
2 - STEERING COLUMN
3 - WIRE HARNESS CONNECTOR
4 - SENTRY KEY IMMOBILIZER MODULE
5 - LOWER SHROUD
6 - SCREW (2)
7 - IGNITION LOCK CYLINDER HOUSING
KJELECTRONIC CONTROL MODULES 8E - 17
SENTRY KEY IMMOBILIZER MODULE (Continued)

INSTALLATION
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE SUPPLEMENTAL RESTRAINT
SYSTEM BEFORE ATTEMPTING ANY STEERING
WHEEL, STEERING COLUMN, DRIVER AIRBAG,
PASSENGER AIRBAG, SEAT BELT TENSIONER,
FRONT IMPACT SENSORS, SIDE CURTAIN AIRBAG,
OR INSTRUMENT PANEL COMPONENT DIAGNOSIS
OR SERVICE. DISCONNECT AND ISOLATE THE
BATTERY NEGATIVE (GROUND) CABLE, THEN
WAIT TWO MINUTES FOR THE SYSTEM CAPACI-
TOR TO DISCHARGE BEFORE PERFORMING FUR-
THER DIAGNOSIS OR SERVICE. THIS IS THE ONLY
SURE WAY TO DISABLE THE SUPPLEMENTAL
RESTRAINT SYSTEM. FAILURE TO TAKE THE
PROPER PRECAUTIONS COULD RESULT IN ACCI-
DENTAL AIRBAG DEPLOYMENT AND POSSIBLE
PERSONAL INJURY.
(1) Position the Sentry Key Immobilizer Module
(SKIM) to the right side of the steering column (Fig.
11). Lift the multi-function switch upward off of the
upper steering column housing far enough to insert
the SKIM antenna ring formation between the igni-
tion key release button and the multi-function switch
housing.
(2) Slide the SKIM antenna ring around the igni-
tion switch lock cylinder housing, then rotate the
SKIM and its mounting bracket upwards and toward
the steering column.
(3) Align the SKIM mounting bracket clip forma-
tion with the right lower flange of the steering col-
umn jacket and, using hand pressure, push upward
firmly and evenly on the connector end of the SKIM
mounting bracket to engage this clip with the steer-
ing column jacket.
(4) Reconnect the instrument panel wire harness
connector for the SKIM to the module connector
receptacle.
(5) Position both the upper and lower shrouds onto
the steering column.
(6) Align the snap features on the lower shroud
with the receptacles on the upper shroud and apply
hand pressure to snap them together.
(7) From below the steering column, install and
tighten the two screws that secure the lower shroud
to the upper shroud. Tighten the screws to 2 N´m (18
in. lbs.).
(8) If the vehicle is equipped with the optional tilt
steering column, move the tilt steering column to the
fully raised position and secure it in place by moving
the tilt release lever back to the locked (up) position.
(9) Reconnect the battery negative cable.NOTE: If the SKIM has been replaced with a new
unit, the Sentry Key Immobilizer System (SKIS)
MUST be initialized before the vehicle can be oper-
ated. (Refer to 8 - ELECTRICAL/VEHICLE THEFT
SECURITY - STANDARD PROCEDURE - SKIS INI-
TIALIZATION).
TRANSMISSION CONTROL
MODULE
DESCRIPTION
The Transmission Control Module (TCM) is located
in the engine compartment on the right (passenger)
side and is mounted to the inner fender (Fig. 12).
OPERATION
The Transmission Control Module (TCM) is the
controlling unit for all electronic operations of the
transmission. The TCM receives information regard-
ing vehicle operation from both direct and indirect
inputs, and selects the operational mode of the trans-
mission. Direct inputs are hardwired to, and used
specifically by the TCM. Indirect inputs originate
from other components/modules, and are shared with
the TCM via the vehicle communication bus.
Some examples ofdirect inputsto the TCM are:
²Battery (B+) voltage
²Ignition ªONº voltage
²Transmission Control Relay (Switched B+)
²Throttle Position Sensor
²Crankshaft Position Sensor
²Transmission Range Sensor
²Pressure Switches
²Transmission Temperature Sensor
²Input Shaft Speed Sensor
Fig. 12 Transmission Control Module Location
1 - Transmission Control Module
8E - 18 ELECTRONIC CONTROL MODULESKJ
SENTRY KEY IMMOBILIZER 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

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)