2002 JEEP LIBERTY Crank sensor

²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Oxygen (O2S) sensors
Based on these inputs, the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then adjust
the injector pulse width by turning the ground circuit
to each individual injector on and off.
²The PCM monitors the O2S sensor input and
adjusts air-fuel ratio. It also adjusts engine idle
speed through the idle air control (IAC) motor.
²The PCM adjusts ignition timing by turning the
ground path to the coil(s) on and off.
²The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.
ACCELERATION MODE
This is an Open Loop mode. The PCM recognizes
an abrupt increase in throttle position or MAP pres-
sure as a demand for increased engine output and
vehicle acceleration. The PCM increases injector
pulse width in response to increased throttle opening.
DECELERATION MODE
When the engine is at operating temperature, this
is an Open Loop mode. During hard deceleration, the
PCM receives the following inputs.
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Vehicle speed
If the vehicle is under hard deceleration with the
proper rpm and closed throttle conditions, the PCM
will ignore the oxygen sensor input signal. The PCM
will enter a fuel cut-off strategy in which it will not
supply a ground to the injectors. If a hard decelera-
tion does not exist, the PCM will determine the
proper injector pulse width and continue injection.Based on the above inputs, the PCM will adjust
engine idle speed through the idle air control (IAC)
motor.
The PCM adjusts ignition timing by turning the
ground path to the coil on and off.
WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the PCM receives the following
inputs.
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
During wide open throttle conditions, the following
occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off. The PCM ignores the oxygen sensor input
signal and provides a predetermined amount of addi-
tional fuel. This is done by adjusting injector pulse
width.
²The PCM adjusts ignition timing by turning the
ground path to the coil(s) on and off.
IGNITION SWITCH OFF MODE
When ignition switch is turned to OFF position,
the PCM stops operating the injectors, ignition coil,
ASD relay and fuel pump relay.
DESCRIPTION - 5 VOLT SUPPLIES
Two different Powertrain Control Module (PCM)
five volt supply circuits are used; primary and sec-
ondary.
DESCRIPTION - IGNITION CIRCUIT SENSE
This circuit ties the ignition switch to the Power-
train Control Module (PCM).
DESCRIPTION - POWER GROUNDS
The Powertrain Control Module (PCM) has 2 main
grounds. Both of these grounds are referred to as
power grounds. All of the high-current, noisy, electri-
cal devices are connected to these grounds as well as
all of the sensor returns. The sensor return comes
into the sensor return circuit, passes through noise
suppression, and is then connected to the power
ground.
The power ground is used to control ground cir-
cuits for the following PCM loads:
²Generator field winding
KJELECTRONIC CONTROL MODULES 8E - 13
POWERTRAIN CONTROL MODULE (Continued)

²Fuel injectors
²Ignition coil(s)
²Certain relays/solenoids
²Certain sensors
DESCRIPTION - SENSOR RETURN
The Sensor Return circuits are internal to the Pow-
ertrain Control Module (PCM).
Sensor Return provides a low±noise ground refer-
ence for all engine control system sensors. Refer to
Power Grounds for more information.
OPERATION
OPERATION - PCM
The PCM operates the fuel system. The PCM is a
pre-programmed, triple microprocessor digital com-
puter. It regulates ignition timing, air-fuel ratio,
emission control devices, charging system, certain
transmission features, speed control, air conditioning
compressor clutch engagement and idle speed. The
PCM can adapt its programming to meet changing
operating conditions.
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as Powertrain Control Module
(PCM) Outputs. The sensors and switches that pro-
vide inputs to the PCM are considered Powertrain
Control Module (PCM) Inputs.
The PCM adjusts ignition timing based upon
inputs it receives from sensors that react to: engine
rpm, manifold absolute pressure, engine coolant tem-
perature, throttle position, transmission gear selec-
tion (automatic transmission), vehicle speed, power
steering pump pressure, and the brake switch.
The PCM adjusts idle speed based on inputs it
receives from sensors that react to: throttle position,
vehicle speed, transmission gear selection, engine
coolant temperature and from inputs it receives from
the air conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
NOTE: PCM Inputs:
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²A/C pressure transducer
²Auto shutdown (ASD) sense
²Battery temperature
²Battery voltage
²Brake switch²J1850 bus (+) circuits
²J1850 bus (-) circuits
²Camshaft position sensor signal
²Crankshaft position sensor
²Data link connection for DRB scan tool
²Engine coolant temperature sensor
²Fuel level (through J1850 circuitry)
²Generator (battery voltage) output
²Ignition circuit sense (ignition switch in on/off/
crank/run position)
²Intake manifold air temperature sensor
²Knock sensors (2 on 3.7L engine)
²Leak detection pump (switch) sense (if equipped)
²Manifold absolute pressure (MAP) sensor
²Oil pressure
²Oxygen sensors
²Park/neutral switch (auto. trans. only)
²Power ground
²Power steering pressure switch
²Sensor return
²Signal ground
²Speed control multiplexed single wire input
²Throttle position sensor
²Transfer case switch (4WD range position)
²Vehicle speed sensor
NOTE: PCM Outputs:
²A/C clutch relay
²Auto shutdown (ASD) relay
²J1850 bus (+/-) circuits for: speedometer, voltme-
ter, fuel gauge, oil pressure gauge/lamp, engine temp.
gauge and speed control warn. lamp
²Clutch pedal position switch override relay
²Data link connection for DRB scan tool
²EGR valve control solenoid (if equipped)
²EVAP canister purge solenoid
²Five volt sensor supply (primary)
²Five volt sensor supply (secondary)
²Fuel injectors
²Fuel pump relay
²Generator field driver (-)
²Generator field driver (+)
²Idle air control (IAC) motor
²Ignition coil(s)
²Leak detection pump (if equipped)
²Malfunction indicator lamp (Check engine lamp).
Driven through J1850 circuits.
²Oxygen sensor heater relays
²Oxygen sensors (pulse width modulated)
²Radiator cooling fan relay (pulse width modu-
lated)
²Speed control vacuum solenoid
²Speed control vent solenoid
²Tachometer (if equipped). Driven through J1850
circuits.
8E - 14 ELECTRONIC CONTROL MODULESKJ
POWERTRAIN CONTROL MODULE (Continued)

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)

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)

IGNITION CONTROL
TABLE OF CONTENTS
page page
IGNITION CONTROL
DESCRIPTION..........................1
OPERATION............................1
SPECIFICATIONS
SPECIFICATIONS - IGNITION TIMING.......2
ENGINE FIRING ORDER - 2.4L 4-CYLINDER . 2
ENGINE FIRING ORDER - 3.7L V-6.........2
IGNITION COIL RESISTANCE - 2.4L........2
IGNITION COIL RESISTANCE - 3.7L V-6.....3
SPARK PLUGS........................3
SPARK PLUG CABLE RESISTANCE - 2.4L . . . 3
TORQUE - IGNITION SYSTEM............3
AUTO SHUT DOWN RELAY
DESCRIPTION - PCM OUTPUT.............4
OPERATION
OPERATION - ASD SENSE - PCM INPUT....4
OPERATION - PCM OUTPUT.............4
DIAGNOSIS AND TESTING - ASD AND FUEL
PUMP RELAYS........................4
REMOVAL.............................5
INSTALLATION..........................5
CAMSHAFT POSITION SENSOR
DESCRIPTION
DESCRIPTION - 2.4L....................5
DESCRIPTION-3.7L.....................6
OPERATION
OPERATION - 2.4L.....................6OPERATION - 3.7L.....................6
REMOVAL.............................7
INSTALLATION..........................8
IGNITION COIL
DESCRIPTION..........................9
OPERATION............................9
REMOVAL.............................10
INSTALLATION.........................10
KNOCK SENSOR
DESCRIPTION.........................11
OPERATION...........................11
REMOVAL.............................12
INSTALLATION.........................12
SPARK PLUG
DESCRIPTION.........................12
OPERATION...........................12
DIAGNOSIS AND TESTING - SPARK PLUG
CONDITIONS.........................13
REMOVAL.............................15
CLEANING SPARK PLUGS................15
INSTALLATION.........................15
IGNITION COIL CAPACITOR
DESCRIPTION.........................16
OPERATION...........................16
REMOVAL.............................16
INSTALLATION.........................16
IGNITION CONTROL
DESCRIPTION
The ignition system consists of:
²Spark Plugs
²Ignition Coil(s)
²Powertrain Control Module (PCM)
²Crankshaft Position Sensor
²2 Knock Sensors (3.7L only)
²Camshaft Position Sensor
²The MAP, TPS, IAC and ECT also have an effect
on the control of the ignition system.
OPERATION
2.4L
A common ignition coil divided into 2 halves is
used. Secondary, high-tension spark plug cables are
also used. One half of the coil fires two spark plugs
simultaneously (one plug is the cylinder under com-pression, and the other plug is the cylinder on the
exhaust stroke). Coil half number one fires cylinders
1 and 4. Coil half number two fires cylinders 2 and 3.
The PCM determines which of the coils to charge and
fire at the correct time.
The Auto Shutdown (ASD) relay provides battery
voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing the coil. When
the PCM breaks the contact, the energy in the coil
primary transfers to the secondary causing a spark.
The PCM will de-energize the ASD relay if it does
not receive inputs from either the crankshaft or cam-
shaft position sensors.
A distributor is not used with the 2.4L engine.
3.7L
The 3.7L V6 engine uses a separate ignition coil for
each cylinder. The one-piece coil bolts directly to the
cylinder head. Rubber boots seal the secondary ter-
minal ends of the coils to the top of all 6 spark plugs.
A separate electrical connector is used for each coil.
KJIGNITION CONTROL 8I - 1

Because of coil design, spark plug cables (second-
ary cables) are not used. A distributor is not used
with the 3.7L engine.
Two knock sensors (one for each cylinder bank) are
used to help control spark knock.
The Auto Shutdown (ASD) relay provides battery
voltage to each ignition coil. The Powertrain Control
Module (PCM) provides a ground contact (circuit) for
energizing each coil. When the PCM breaks the con-
tact, the energy in the coil primary transfers to the
secondary causing a spark. The PCM will de-energize
the ASD relay if it does not receive inputs from
either the crankshaft or camshaft position sensors.
SPECIFICATIONS
SPECIFICATIONS - IGNITION TIMING
Ignition timing is not adjustable on any
engine.
ENGINE FIRING ORDER - 2.4L 4-CYLINDER1-3-4-2
ENGINE FIRING ORDER - 3.7L V-61-6-5-4-3-2
IGNITION COIL RESISTANCE - 2.4L
Engine Coil ManufacturePrimary Resistance at
21ÉC-27ÉC (70ÉF-80ÉF)Secondary Resistance at
21ÉC-27ÉC (70ÉF-80ÉF)
2.4L Toyodenso or Diamond 0.51 to 0.61 Ohms 11,500 to 13,500 Ohms
Fig. 1 IGNITION COIL - 2.4L
8I - 2 IGNITION CONTROLKJ
IGNITION CONTROL (Continued)

IGNITION COIL RESISTANCE - 3.7L V-6
PRIMARY RESISTANCE
21-27ÉC (70-80ÉF)SECONDARY
RESISTANCE 21-27ÉC
(70-80ÉF)
0.6 - 0.9 Ohms 6,000 - 9,000 Ohms
SPARK PLUGS
ENGINE PLUG TYPE ELECTRODE GAP
2.4L RE14MCC5 (Champion #) 1.24 to 1.37 mm (0.048 to 0.053 in.)
3.7L V-6 2FR6F - 11G (NGK #) 1.1 mm (0.042 in.)
SPARK PLUG CABLE RESISTANCE - 2.4L
MINIMUM MAXIMUM
250 Ohms Per Inch 1000 Ohms Per Inch
3000 Ohms Per Foot 12,000 Ohms Per Foot
TORQUE - IGNITION SYSTEM
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Camshaft Position Sensor-2.4L 23 21 205
Camshaft Position Sensor±3.7L 12 - 106
Crankshaft Position Sensor Bolt-2.4L 12 - 106
Crankshaft Position Sensor Nut/Bolt-3.7L 23 21 205
* Knock Sensor Bolt - 3.7L * 20 * 15
Ignition Coil Mounting Bolts - 2.4L 11 - 105
Ignition Coil Mounting Nuts - 3.7L 8 - 70
Ignition Coil Capacitor Nuts- 3.7L 8 - 70
** Spark Plugs - 2.4L ** 15 ** 11 -
Spark Plugs - 3.7L 27 20 -
* Do not apply any sealant, thread-locker or adhesive to
bolts. Poor sensor performance may result.
** Torque critical tapered design. Do not exceed 15 ft. lbs.
KJIGNITION CONTROL 8I - 3
IGNITION CONTROL (Continued)

DESCRIPTION-3.7L
The Camshaft Position Sensor (CMP) on the 3.7L
6±cylinder engine is bolted to the right-front side of
the right cylinder head (Fig. 6).
OPERATION
OPERATION - 2.4L
The Camshaft Position Sensor (CMP) sensor con-
tains a hall effect device referred to as a sync signal
generator. A rotating target wheel (tonewheel) for the
CMP is located behind the exhaust valve-camshaft
drive gear (Fig. 7). The target wheel is equipped with
a cutout (notch) around 180 degrees of the wheel.
The CMP detects this cutout every 180 degrees of
camshaft gear rotation. Its signal is used in conjunc-
tion with the Crankshaft Position Sensor (CKP) to
differentiate between fuel injection and spark events.
It is also used to synchronize the fuel injectors with
their respective cylinders.
When the leading edge of the target wheel cutout
enters the tip of the CMP, the interruption of mag-
netic field causes the voltage to switch high, result-
ing in a sync signal of approximately 5 volts.
When the trailing edge of the target wheel cutout
leaves the tip of the CMP, the change of the magnetic
field causes the sync signal voltage to switch low to 0
volts.
OPERATION - 3.7L
The Camshaft Position Sensor (CMP) sensor con-
tains a hall effect device referred to as a sync signal
generator. A rotating target wheel (tonewheel) for the
CMP is located at the front of the camshaft for the
right cylinder head (Fig. 8). This sync signal genera-
tor detects notches located on a tonewheel. As the
tonewheel rotates, the notches pass through the sync
signal generator. The signal from the CMP sensor is
used in conjunction with the Crankshaft Position
Sensor (CKP) to differentiate between fuel injection
and spark events. It is also used to synchronize the
fuel injectors with their respective cylinders.
When the leading edge of the tonewheel notch
enters the tip of the CMP, the interruption of mag-
netic field causes the voltage to switch high, result-
ing in a sync signal of approximately 5 volts.
When the trailing edge of the tonewheel notch
leaves then tip of the CMP, the change of the mag-
netic field causes the sync signal voltage to switch
low to 0 volts.
Fig. 6 CAMSHAFT POSITION SENSOR - 3.7L
1 - RIGHT/FRONT OF RIGHT CYLINDER HEAD
2 - CMP MOUNTING BOLT
3 - CMP LOCATION
Fig. 7 CMP FACE AT TARGET WHEEL-2.4L
1 - CAMSHAFT DRIVE GEAR
2 - TARGETWHEEL (TONEWHEEL)
3 - FACE OF CMP SENSOR
4 - CUTOUT (NOTCH)
8I - 6 IGNITION CONTROLKJ
CAMSHAFT POSITION SENSOR (Continued)