2002 JEEP LIBERTY engine

AUTO SHUT DOWN RELAY
DESCRIPTION - PCM OUTPUT
The 5±pin, 12±volt, Automatic Shutdown (ASD)
relay is located in the Power Distribution Center
(PDC). Refer to label on PDC cover for relay location.
OPERATION
OPERATION - ASD SENSE - PCM INPUT
A 12 volt signal at this input indicates to the PCM
that the ASD has been activated. The relay is used to
connect the oxygen sensor heater elements, oxygen
sensor heater relay, ignition coil and fuel injectors to
12 volt + power supply.
This input is used only to sense that the ASD relay
is energized. If the Powertrain Control Module
(PCM) does not see 12 volts at this input when the
ASD should be activated, it will set a Diagnostic
Trouble Code (DTC).
OPERATION - PCM OUTPUT
The ASD relay supplies battery voltage (12+ volts)
to the fuel injectors and ignition coil(s). With certain
emissions packages it also supplies 12±volts to the
oxygen sensor heating elements and the oxygen sen-
sor heater relay.
The ground circuit for the coil within the ASD
relay is controlled by the Powertrain Control Module
(PCM). The PCM operates the ASD relay by switch-
ing its ground circuit on and off.
The ASD relay will be shut±down, meaning the
12±volt power supply to the ASD relay will be de-ac-
tivated by the PCM if the ignition key is left in the
ON position. This is if the engine has not been run-
ning for approximately 1.8 seconds.
DIAGNOSIS AND TESTING - ASD AND FUEL
PUMP RELAYS
The following description of operation and
tests apply only to the Automatic Shutdown
(ASD) and fuel pump relays. The terminals on the
bottom of each relay are numbered. Two different
types of relays may be used, (Fig. 2) or (Fig. 3).
²Terminal number 30 is connected to battery volt-
age. For both the ASD and fuel pump relays, termi-
nal 30 is connected to battery voltage at all times.
²The PCM grounds the coil side of the relay
through terminal number 85.
²Terminal number 86 supplies voltage to the coil
side of the relay.
²When the PCM de-energizes the ASD and fuel
pump relays, terminal number 87A connects to termi-
nal 30. This is the Off position. In the off position,voltage is not supplied to the rest of the circuit. Ter-
minal 87A is the center terminal on the relay.
²When the PCM energizes the ASD and fuel
pump relays, terminal 87 connects to terminal 30.
This is the On position. Terminal 87 supplies voltage
to the rest of the circuit.
The following procedure applies to the ASD and
fuel pump relays.
(1) Remove relay from connector before testing.
(2) With the relay removed from the vehicle, use
an ohmmeter to check the resistance between termi-
nals 85 and 86. The resistance should be 75 ohms +/-
5 ohms.
(3) Connect the ohmmeter between terminals 30
and 87A. The ohmmeter should show continuity
between terminals 30 and 87A.
Fig. 2 TYPE 1 RELAY (ISO MICRO RELAY)
Fig. 3 ASD AND FUEL PUMP RELAY TERMINALSÐ
TYPE 2
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
8I - 4 IGNITION CONTROLKJ

(4) Connect the ohmmeter between terminals 87
and 30. The ohmmeter should not show continuity at
this time.
(5) Connect one end of a jumper wire (16 gauge or
smaller) to relay terminal 85. Connect the other end
of the jumper wire to the ground side of a 12 volt
power source.
(6) Connect one end of another jumper wire (16
gauge or smaller) to the power side of the 12 volt
power source.Do not attach the other end of the
jumper wire to the relay at this time.
WARNING: DO NOT ALLOW OHMMETER TO CON-
TACT TERMINALS 85 OR 86 DURING THIS TEST.
DAMAGE TO OHMMETER MAY RESULT.
(7) Attach the other end of the jumper wire to
relay terminal 86. This activates the relay. The ohm-
meter should now show continuity between relay ter-
minals 87 and 30. The ohmmeter should not show
continuity between relay terminals 87A and 30.
(8) Disconnect jumper wires.
(9) Replace the relay if it did not pass the continu-
ity and resistance tests. If the relay passed the tests,
it operates properly. Check the remainder of the ASD
and fuel pump relay circuits. Refer to 8, Wiring Dia-
grams.
REMOVAL
The ASD relay is located in the Power Distribution
Center (PDC) (Fig. 4). Refer to label on PDC cover
for relay location.(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
The ASD relay is located in the Power Distribution
Center (PDC). Refer to label on PDC cover for relay
location.
(1) Install relay to PDC.
(2) Install cover to PDC.
CAMSHAFT POSITION
SENSOR
DESCRIPTION
DESCRIPTION - 2.4L
The Camshaft Position Sensor (CMP) on the 2.4L
4±cylinder engine is bolted to the right-front side of
the cylinder head (Fig. 5).
Fig. 4 POWER DISTRIBUTION CENTER (PDC)
1 - BATTERY
2 - PDC
3 - PDC COVER
Fig. 5 CMP LOCATION - 2.4L
1 - CMP SENSOR
2 - ELECTRICAL CONNECTOR
3-
4 - SLOTTED HOLES
5 - MOUNTING BOLTS (2)
KJIGNITION CONTROL 8I - 5
AUTO SHUT DOWN RELAY (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)

REMOVAL
2.4L
The Camshaft Position Sensor (CMP) on the 2.4L
4±cylinder engine is bolted to the right-front side of
the cylinder head (Fig. 9). Sensor position (depth) is
adjustable.
(1) Disconnect electrical connector at CMP sensor.
(2) Remove 2 sensor mounting bolts.
(3) Remove sensor from cylinder head by sliding
towards rear of engine.
3.7L
The Camshaft Position Sensor (CMP) on the 3.7L
V-6 engine is bolted to the front/top of the right cyl-
inder head (Fig. 10).
(1) Disconnect electrical connector at CMP sensor.
(2) Remove sensor mounting bolt (Fig. 10).
(3) Carefully remove sensor from cylinder head in
a rocking and twisting action. Twisting sensor eases
removal.
(4) Check condition of sensor o-ring.
Fig. 8 CAMSHAFT POSITION SENSOR LOCATION -
3.7L
1 - NOTCHES
2 - RIGHT CYLINDER HEAD
3 - CMP
4 - TONEWHEEL (TARGET WHEEL)
Fig. 9 CMP LOCATION - 2.4L
1 - CMP SENSOR
2 - ELECTRICAL CONNECTOR
3-
4 - SLOTTED HOLES
5 - MOUNTING BOLTS (2)
Fig. 10 CAMSHAFT POSITION SENSOR (CMP) - 3.7L
1 - RIGHT/FRONT OF RIGHT CYLINDER HEAD
2 - CMP MOUNTING BOLT
3 - CMP LOCATION
KJIGNITION CONTROL 8I - 7
CAMSHAFT POSITION SENSOR (Continued)

INSTALLATION
2.4L
The Camshaft Position Sensor (CMP) on the 2.4L
4±cylinder engine is bolted to the right-front side of
the cylinder head.Sensor position (depth) is
adjustable.
(1) Remove plastic, upper timing belt cover (timing
gear cover) (Fig. 11) by removing 3 bolts. Before
attempting to remove cover, remove electrical connec-
tor from Engine Coolant Temperature (ECT) sensor
(Fig. 11). This will prevent damage to sensor.
(2) Rotate (bump over) engine until camshaft tim-
ing gear and target wheel (tonewheel) are positioned
and aligned to face of sensor as shown in (Fig. 12).If
not positioned as shown in (Fig. 12), damage to
both sensor and target wheel will occur when
attempting to start engine. Face of sensor
MUST be behind target wheel while adjusting.
(3) Position sensor to cylinder head and install 2
sensor mounting bolts finger tight.
(4)SENSOR AIR GAP: .030ºSet air gap between
rear of target wheel and face of sensor to .030º. This
can best be accomplished using an L-shaped, wire-
type spark plug gapping gauge (Fig. 13). A piece of
.030º brass shim stock may also be used.
(5) Gently push sensor forward until it contacts
gapping gauge.Do not push hard on sensor.
Tighten 2 sensor mounting bolts. Refer to torque
specifications.CAUTION: After tightening sensor mounting bolts,
recheck air gap and adjust as necessary. Retorque
bolts.
(6) Install upper timing belt cover and 3 bolts.
(7) Connect electrical connector to ECT sensor.
(8) Connect electrical connector to CMP sensor.
Fig. 11 UPPER TIMING BELT COVER/BOLTS-2.4L
1 - UPPER TIMING BELT COVER
2 - ELECTRICAL CONNECTOR (ECT)
3 - MOUNTING BOLTS (3)
Fig. 12 CMP FACE AT TARGET WHEEL-2.4L
1 - CAMSHAFT DRIVE GEAR
2 - TARGETWHEEL (TONEWHEEL)
3 - FACE OF CMP SENSOR
4 - CUTOUT (NOTCH)
Fig. 13 CMP ADJUSTMENT - 2.4L
1 - FACE OF SENSOR
2 - WIRE GAPPING TOOL
8I - 8 IGNITION CONTROLKJ
CAMSHAFT POSITION SENSOR (Continued)

3.7L
The Camshaft Position Sensor (CMP) on the 3.7L
V-6 engine is bolted to the front/top of the right cyl-
inder head.
(1) Clean out machined hole in cylinder head.
(2) Apply a small amount of engine oil to sensor
o-ring.
(3) Install sensor into cylinder head with a slight
rocking and twisting action.
CAUTION: Before tightening sensor mounting bolt,
be sure sensor is completely flush to cylinder head.
If sensor is not flush, damage to sensor mounting
tang may result.
(4) Install mounting bolt and tighten. Refer to
torque specifications.
(5) Connect electrical connector to sensor.
IGNITION COIL
DESCRIPTION
2.4L
The coil assembly consists of 2 different coils
molded together. The assembly is mounted to the top
of the engine (Fig. 14).
3.7L
The 3.7L V-6 engine uses 6 dedicated, and individ-
ually fired coil for each spark plug (Fig. 15). Each
coil is mounted directly into the cylinder head and
onto the top of each spark plug (Fig. 16).
OPERATION
2.4L
The coil fires two spark plugs simultaneously. One
plug is under compression, the other plug fires on the
exhaust stroke (lost spark). Coil number one fires
Fig. 14 IGNITION COIL - 2.4L
1 - IGNITION COIL
2 - MOUNTING BOLTS (4)
Fig. 15 IGNITION COIL - 3.7L
1 - O-RING
2 - IGNITION COIL
3 - ELECTRICAL CONNECTOR
Fig. 16 IGNITION COIL LOCATION - 3.7L
1 - IGNITION COIL
2 - COIL MOUNTING NUT
KJIGNITION CONTROL 8I - 9
CAMSHAFT POSITION SENSOR (Continued)

cylinders 1 and 4, and coil number two fires cylinders
2 and 3.
The Auto Shutdown (ASD) relay provides battery
voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing the coil(s). The
PCM will de-energize the ASD relay if it does not
receive the crankshaft position sensor and camshaft
position sensor inputs.
Base ignition timing is not adjustable.By con-
trolling the coil ground circuit, the PCM is able to set
the base timing and adjust the ignition timing
advance. This is done to meet changing engine oper-
ating conditions.
The ignition coil is not oil filled. The windings are
embedded in an epoxy compound. This provides heat
and vibration resistance that allows the ignition coil
to be mounted on the engine.
Spark plug cables (secondary wires or cables) are
used with the 2.4L engine.
3.7L
Battery voltage is supplied to the 6 ignition coils
from the ASD relay. The Powertrain Control Module
(PCM) opens and closes each ignition coil ground cir-
cuit at a determined time for ignition coil operation.
Base ignition timing is not adjustable.By con-
trolling the coil ground circuit, the PCM is able to set
the base timing and adjust the ignition timing
advance. This is done to meet changing engine oper-
ating conditions.
The ignition coil is not oil filled. The windings are
embedded in an epoxy compound. This provides heat
and vibration resistance that allows the ignition coil
to be mounted on the engine.
Because of coil design, spark plug cables (second-
ary cables) are not used with the 3.7L engine.
REMOVAL
2.4L
(1) Disconnect electrical connector at rear of coil.
(2) Remove all secondary cables from coil.
(3) Remove 4 coil mounting bolts (Fig. 17).
(4) Remove coil from vehicle.
3.7L
An individual ignition coil is used for each spark
plug (Fig. 19). The coil fits into machined holes in the
cylinder head. A mounting stud/nut secures each coil
to the top of the intake manifold (Fig. 18). The bot-
tom of the coil is equipped with a rubber boot to seal
the spark plug to the coil. Inside each rubber boot is
a spring. The spring is used for a mechanical contact
between the coil and the top of the spark plug. These
rubber boots and springs are a permanent part of the
coil and are not serviced separately. An o-ring (Fig.19) is used to seal the coil at the opening into the cyl-
inder head.
(1) Depending on which coil is being removed, the
throttle body air intake tube or intake box may need
to be removed to gain access to coil.
(2) Disconnect electrical connector from coil by
pushing downward on release lock on top of connec-
tor and pull connector from coil.
(3) Clean area at base of coil with compressed air
before removal.
(4) Remove coil mounting nut from mounting stud
(Fig. 18).
(5) Carefully pull up coil from cylinder head open-
ing with a slight twisting action.
(6) Remove coil from vehicle.
INSTALLATION
2.4L
(1) Position coil to engine.
(2) Install 4 mounting bolts. Refer to torque speci-
fications.
(3) Install secondary cables.
(4) Install electrical connector at rear of coil.
(5) Install air cleaner tube and housing.
3.7L
(1) Using compressed air, blow out any dirt or con-
taminants from around top of spark plug.
(2) Check condition of coil o-ring and replace as
necessary. To aid in coil installation, apply silicone to
coil o-ring.
Fig. 17 IGNITION COIL - 2.4L
1 - IGNITION COIL
2 - MOUNTING BOLTS (4)
8I - 10 IGNITION CONTROLKJ
IGNITION COIL (Continued)

(3) Position ignition coil into cylinder head opening
and push onto spark plug. Do this while guiding coil
base over mounting stud.
(4) Install coil mounting stud nut. Refer to torque
specifications.(5) Connect electrical connector to coil by snapping
into position.
(6) If necessary, install throttle body air tube or
box.
KNOCK SENSOR
DESCRIPTION
The 2 knock sensors are bolted into the cylinder
block under the intake manifold. The sensors are
used only with the 3.7L engine.
OPERATION
Two knock sensors are used on the 3.7L V-6
engine; one for each cylinder bank. When the knock
sensor detects a knock in one of the cylinders on the
corresponding bank, it sends an input signal to the
Powertrain Control Module (PCM). In response, the
PCM retards ignition timing for all cylinders by a
scheduled amount.
Knock sensors contain a piezoelectric material
which constantly vibrates and sends an input voltage
(signal) to the PCM while the engine operates. As the
intensity of the crystal's vibration increases, the
knock sensor output voltage also increases.
The voltage signal produced by the knock sensor
increases with the amplitude of vibration. The PCM
receives the knock sensor voltage signal as an input.
If the signal rises above a predetermined level, the
PCM will store that value in memory and retard
ignition timing to reduce engine knock. If the knock
sensor voltage exceeds a preset value, the PCM
retards ignition timing for all cylinders. It is not a
selective cylinder retard.
The PCM ignores knock sensor input during engine
idle conditions. Once the engine speed exceeds a
specified value, knock retard is allowed.
Knock retard uses its own short term and long
term memory program.
Long term memory stores previous detonation
information in its battery-backed RAM. The maxi-
mum authority that long term memory has over tim-
ing retard can be calibrated.
Short term memory is allowed to retard timing up
to a preset amount under all operating conditions (as
long as rpm is above the minimum rpm) except at
Wide Open Throttle (WOT). The PCM, using short
term memory, can respond quickly to retard timing
when engine knock is detected. Short term memory
is lost any time the ignition key is turned off.
Fig. 18 IGNITION COIL LOCATION - 3.7L
1 - IGNITION COIL
2 - COIL MOUNTING NUT
Fig. 19 IGNITION COIL - 3.7L
1 - O-RING
2 - IGNITION COIL
3 - ELECTRICAL CONNECTOR
KJIGNITION CONTROL 8I - 11
IGNITION COIL (Continued)