1995 JEEP YJ ignition

For a complete operational description of all
DTC's, for accessing a DTC and for erasing aDTC, refer to On-Board Diagnostics. This can
be found in the General Diagnosis sections of
Group 14, Fuel System. For numeric flash lamp
code charts, refer to Diagnostic Trouble Code
(DTC). This can also be found in the General
Diagnosis sections of Group 14, Fuel System.
Fig. 28 Check Engine LampÐXJ ModelsÐTypicalFig. 29 Check Engine LampÐYJ ModelsÐTypical
8D - 16 IGNITION SYSTEMSJ

COMPONENT REMOVAL/INSTALLATION
INDEX
page page
Automatic Shutdown (ASD) Relay............. 17
Camshaft Position Sensor................... 17
Crankshaft Position Sensor.................. 17
Distributor............................... 19
Engine Coolant Temperature Sensor........... 19
General Information....................... 17
Ignition Coil............................. 22Intake Manifold Air Temperature Sensor......... 23
Manifold Absolute Pressure (MAP) Sensor....... 23
Oxygen (O2S) Sensor...................... 23
Powertrain Control Module (PCM)............. 23
Spark Plug Secondary Cables................ 24
Spark Plugs............................. 23
Throttle Position Sensor (TPS)............... 25
GENERAL INFORMATION
This section of the group, Component Removal/In-
stallation, will discuss the removal and installation
of ignition system components.
For basic ignition system diagnostics and service
adjustments, refer to the Diagnostics/Service Proce-
dures section of this group.
For system operation and component identification,
refer to the Component Identification/System Opera-
tion section of this group.
AUTOMATIC SHUTDOWN (ASD) RELAY
The ASD relay is installed in the power distribu-
tion center (PDC) (Figs. 1 or 2). Relay location is
printed on the PDC cover.
REMOVAL
(1) Remove the PDC cover.
(2) Remove the relay by lifting straight up.
INSTALLATION
(1) Check the condition of relay wire terminals at
PDC before installing relay. Repair as necessary.
(2) Push the relay into the connector.
(3) Install the relay cover.
CAMSHAFT POSITION SENSOR
The camshaft position sensor is located in the dis-
tributor (Fig. 3).
REMOVAL
Distributor removal is not necessary to remove
camshaft position sensor.
(1) Disconnect negative battery cable at battery.
(2) Remove distributor cap from distributor (two
screws).
(3) Disconnect camshaft position sensor wiring
harness from main engine wiring harness.
(4) Remove distributor rotor from distributor shaft.
(5) Lift the camshaft position sensor assembly
from the distributor housing (Fig. 3).
INSTALLATION
(1) Install camshaft position sensor to distributor.
Align sensor into notch on distributor housing.
(2) Connect wiring harness.
(3) Install rotor.
(4) Install distributor cap. Tighten mounting
screws.
CRANKSHAFT POSITION SENSOR
The crankshaft position sensor is mounted in the
Fig. 1 PDCÐXJ Models
Fig. 2 PDCÐYJ Models
JIGNITION SYSTEMS 8D - 17

transmission bellhousing at the left/rear side of the
engine block (Figs. 4, 5 or 6).
On all 2.5L 4-cylinder and 4.0L 6-cylinder engines
(except YJ models with an automatic transmission
and 4.0L 6-cylinder engine) the sensor is attached
with two bolts. The 2.5L 4-cylinder engine, when
equipped with an automatic transmission, will have
the sensor mounted with two nuts.
On YJ models with a 4.0L 6-cylinder engine and
automatic transmission, the sensor is attached with a
single bolt (Fig. 6).
REMOVALÐALL ENGINES
(1) Near the rear of the intake manifold, discon-
nect the pigtail harness (on the sensor) from the
main electrical harness.
(2) Remove the nut holding sensor wire clip to fuel
rail mounting stud.
(3) Depending upon application, remove either the
sensor mounting bolt(s) or nuts.
(4) Remove the sensor.(5) Remove clip from sensor wire harness.
INSTALLATIONÐALL EXCEPT YJ MODELS
WITH 4.0L 6-CYLINDER ENGINE AND
AUTOMATIC TRANSMISSION
(1) Install the sensor flush against the opening in
the transmission housing.
(2) Install and tighten the two sensor mounting
bolts (or nuts) to 19 Nzm (14 ft. lbs.) torque.
Fig. 3 Camshaft Position Sensor
Fig. 4 Crankshaft Position SensorÐ2.5L 4-Cylinder
EngineÐTypical
Fig. 5 Crankshaft Position SensorÐ4.0L 6-Cylinder
EngineÐAll Except YJ models With Automatic
Transmission
Fig. 6 Crankshaft Position SensorÐ4.0L 6-Cylinder
EngineÐYJ models With Automatic Transmission
8D - 18 IGNITION SYSTEMSJ

CAUTION: On some models, two bolts are used to
secure the sensor to the transmission. These bolts
are specially machined to correctly space the unit
to the flywheel. Do not attempt to install any other
bolts.
(3) Connect the electrical connector to the sensor.
(4) Install clip on sensor wire harness.
(5) Install clip over fuel rail mounting stud. Install
clip mounting nut.
INSTALLATIONÐYJ MODELS WITH 4.0L
6-CYLINDER ENGINE AND AUTOMATIC
TRANSMISSION
(1) Install the sensor into the access hole on the
transmission.
(2) Install sensor mounting bolt (Fig. 6).
(3) Tighten sensor mounting bolt to 6-to-8 Nzm (50-
to-70 in. lbs.) torque.
(4) Connect the electrical connector to sensor.
(5) Install the clip to sensor wire harness.
(6) Install clip over fuel rail mounting stud. Install
clip mounting nut.
ENGINE COOLANT TEMPERATURE SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
DISTRIBUTOR
GENERAL INFORMATION
All distributors contain an internal oil seal that
prevents oil from entering the distributor housing.
The seal is not serviceable.
Factory replacement distributors are equipped with
a plastic alignment pin already installed. The pin is
located in an access hole on the bottom of the distrib-
utor housing (Fig. 7). It is used to temporarily lock
the rotor to the cylinder number 1 position during in-
stallation. The pin must be removed after installing
the distributor.
The camshaft position sensor is located in the dis-
tributor on all engines (Fig. 8). For removal/installa-
tion procedures, refer to Camshaft Position Sensor.
Distributor removal is not necessary for sensor re-
moval.
Refer to figure 8 for an exploded view of the dis-
tributor.
A fork with a slot is supplied on the bottom of the
distributor housing where the housing base seats
against the engine block (Fig. 8). The centerline of
the slot aligns with the distributor holddown bolt
hole in the engine block. Because of the fork, the dis-
tributor cannot be rotated. Distributor rotation is not
necessary as all ignition timing requirements are
handled by the powertrain control module (PCM).The position of the distributor determines fuel syn-
chronization only. It does not determine ignition tim-
ing.
Do not attempt to modify this fork to attain
ignition timing.
Fig. 7 Plastic Alignment Pin
Fig. 8 DistributorÐ2.5L Or 4.0L EnginesÐTypical
JIGNITION SYSTEMS 8D - 19

REMOVALÐ2.5L OR 4.0L ENGINE
(1) Disconnect the negative battery cable at the
battery.
(2) Disconnect coil secondary cable at coil.
(3) Remove distributor cap from distributor (2
screws). Do not remove cables from cap. Do not re-
move rotor.
(4) Disconnect the distributor wiring harness from
the main engine harness.
(5) Remove the cylinder number 1 spark plug.
(6) Hold a finger over the open spark plug hole.
Rotate the engine at the vibration dampener bolt un-
til compression (pressure) is felt.
Slowly continue to rotate the engine. Do this until
the timing index mark on the vibration damper pul-
ley aligns with the top dead center (TDC) mark (0
degree) on timing degree scale (Fig. 9). Always rotate
the engine in direction of normal rotation. Do not ro-
tate the engine backward to align the timing marks.
On XJ models equipped with A/C, remove the elec-
trical cooling fan and shroud assembly from the radi-
ator. Refer to Group 7, Cooling System for
procedures.
This will provide room to turn the engine crank-
shaft with a socket and ratchet using the vibration
damper bolt.
(7) Remove the distributor holddown bolt and
clamp (Fig. 8).
(8) Remove the distributor from engine by slowly
lifting straight up.
Note that the rotor will rotate slightly in a counter-
clockwise direction while lifting up the distributor.
The oil pump gear will also rotate slightly in a coun-terclockwise direction while lifting up the distributor.
This is due to the helical cut gears on the distributor
and camshaft.
Note the removed position of the rotor during dis-
tributor removal. During installation, this will be re-
ferred to as the Pre-position.
2.5L 4-Cylinder Engine:Observe the slot in the
oil pump gear through the hole on the side of the en-
gine. It should be slightly before (counterclockwise of)
the 10 o'clock position (Fig. 10).
4.0L 6-Cylinder Engine:Observe the slot in the
oil pump gear through the hole on the side of the en-
gine. It should be slightly before (counterclockwise of)
the 11 o'clock position (Fig. 11).
(9) Remove and discard the old distributor-to-en-
gine block gasket (Fig. 8).
INSTALLATION
(1) If the engine crankshaft has been rotated after
distributor removal, cylinder number 1 must be re-
turned to its proper firing stroke. Refer to the previ-
ous REMOVAL steps number 5 and 6. These steps
must be done before installing distributor.
Fig. 9 Align Timing Marks
Fig. 10 Slot At 10 O'clock PositionÐ2.5L Engine
Fig. 11 Slot At 11 O'clock PositionÐ4.0L Engine
8D - 20 IGNITION SYSTEMSJ

(2) Check the position of the slot on the oil pump
gear. On the 2.5L engine, it should be just slightly
before (counterclockwise of) the 10 o'clock position
(Fig. 10). On the 4.0L engine, it should be just
slightly before (counterclockwise of) the 11 o'clock po-
sition (Fig. 11). If not, place a flat blade screwdriver
into the oil pump gear and rotate it into the proper
position.
(3) Factory replacement distributors are equipped
with a plastic alignment pin already installed (Fig.
7). This pin is used to temporarily hold the rotor to
the cylinder number 1 firing position during distrib-
utor installation. If this pin is in place, proceed to
step number 8. If not, proceed to step number 4.
(4) If the original distributor is to be reinstalled,
such as during engine overhaul, the plastic pin will
not be available. A 3/16 inch drift pin punch tool may
be substituted for the plastic pin.
(5) Remove the camshaft position sensor from the
distributor housing. Lift straight up.
(6) Four different alignment holes are provided on
the plastic ring (Fig. 12).Note that 2.5L and 4.0L
engines have different alignment holes (Fig.
12).
(7) Rotate the distributor shaft and install the pin
punch tool through the proper alignment hole in the
plastic ring (Fig. 12) and into the mating access hole
in the distributor housing. This will prevent the dis-
tributor shaft and rotor from rotating.
(8) Clean the distributor mounting hole area of the
engine block.
(9) Install a new distributor-to-engine block gasket
(Fig. 8).
(10) Install the rotor to the distributor shaft.(11)2.5L 4-Cylinder Engine:Pre-position the dis-
tributor into the engine while holding the centerline
of the base slot in the 1 o'clock position (Fig. 13).
Continue to engage the distributor into the engine.
The rotor and distributor will rotate clockwise during
installation. This is due to the helical cut gears on
the distributor and camshaft. When the distributor is
fully seated to the engine block, the centerline of the
base slot should be aligned to the clamp bolt mount-
ing hole on the engine (Fig. 14). The rotor should
also be pointed slightly past (clockwise of) the 3
o'clock position.
4.0L 6-Cylinder Engine:Pre-position the distrib-
utor into the engine while holding the centerline of
the base slot in the 1 o'clock position (Fig. 13). Con-
tinue to engage the distributor into the engine. The
rotor and distributor will rotate clockwise during in-
stallation. This is due to the helical cut gears on the
distributor and camshaft. When the distributor is
fully seated to the engine block, the centerline of the
base slot should be aligned to the clamp bolt mount-
ing hole on the engine (Fig. 15). The rotor should
also be pointed at the 5 o'clock position.
It may be necessary to rotate the rotor and distrib-
utor shaft (very slightly) to engage the distributor
shaft with the slot in the oil pump gear. The same
may have to be done to engage the distributor gear
with the camshaft gear.
The distributor is correctly installed when:
²the rotor is pointed at the 3 o'clock position (2.5L
engine), or at the 5 o'clock position (4.0L engine).
²the plastic alignment pin (or pin punch tool) is still
installed to distributor.
Fig. 12 Pin Alignment HolesFig. 13 Distributor Pre-positionÐAll Engines
JIGNITION SYSTEMS 8D - 21

²the number 1 cylinder piston is set at top dead
center (TDC) (compression stroke).
²the centerline of the slot at the base of the distrib-
utor is aligned to the centerline of the distributor
holddown bolt hole on the engine. In this position,
the holddown bolt should easily pass through the slot
and into the engine.
No adjustments are necessary. Proceed to next
step.(12) Install the distributor holddown clamp and
bolt. Tighten the bolt to 23 Nzm (17 ft. lbs.) torque.
(13) Remove the pin punch tool from the distribu-
tor. Or, if the plastic alignment pin was used, remove
it straight down from the bottom of the distributor.
Discard plastic pin.
(14) If removed, install the camshaft position sen-
sor to the distributor. Align the wiring harness grom-
met to the notch in the distributor housing.
(15) Install the rotor.
CAUTION: If the distributor cap is incorrectly posi-
tioned on distributor housing, the cap or rotor may
be damaged when engine is started.
(16) Install the distributor cap. Tighten distributor
cap holddown screws to 3 Nzm (26 in. lbs.) torque.
(17) If removed, install the spark plug cables to
the distributor cap. For proper firing order, refer to
the Specifications section at the end of this group.
See Engine Firing Order.
(18) Connect the distributor wiring harness to the
main engine harness.
(19) Connect battery cable to battery.
IGNITION COIL
The ignition coil is an epoxy filled type. If the coil
is replaced, it must be replaced with the same type.
REMOVAL
On the 2.5L 4-cylinder engine, the ignition coil is
mounted to a bracket on the side of the engine (to
the rear of the distributor).
On the 4.0L 6-cylinder engine, the ignition coil is
mounted to a bracket on the side of the engine (to
the front of the distributor) (Fig. 16).
(1) Disconnect the ignition coil secondary cable
from ignition coil (Fig. 16).
(2) Disconnect engine harness connector from igni-
tion coil.
Fig. 14 Distributor Engaged PositionÐ2.5L
4-Cylinder Engine
Fig. 15 Distributor Engaged PositionÐ4.0L
6-Cylinder Engine
Fig. 16 Ignition CoilÐTypical (4.0L Shown)
8D - 22 IGNITION SYSTEMSJ

(3) Remove ignition coil mounting bolts (nuts are
used on back side of bracket). Remove coil.
INSTALLATION
(1) Install ignition coil to bracket on cylinder block
with mounting bolts and nuts.
(2) Connect engine harness connector to coil.
(3) Connect ignition coil cable to ignition coil.
INTAKE MANIFOLD AIR TEMPERATURE SENSOR
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
OXYGEN (O2S) SENSOR
For an operational description, diagnosis or remov-
al/ installation procedures, refer to Group 14, Fuel
Systems.
POWERTRAIN CONTROL MODULE (PCM)
The PCM was formerly referred to as the SBEC or
engine controller.
XJ MODELS
On XJ models, the PCM is located in the engine
compartment next to the air cleaner (Fig. 17).
REMOVAL
(1) Disconnect negative battery cable at battery.
(2) Loosen 60-way connector mounting screw until
connector can be disengaged from PCM.
(3) Pull 60-way connector straight back from PCM.
(4) Remove PCM mounting bolts.
(5) Remove PCM from vehicle.INSTALLATION
(1) Check the pins in the PCM 60-way electrical
connector for damage. Repair as necessary.
(2) Install PCM. Tighten mounting bolts to 1 Nzm
(9 in. lbs.) torque.
(3) Engage 60-way connector into PCM. Tighten
connector mounting screw to 4 Nzm (35 in. lbs.)
torque.
(4) Connect battery cable to battery.
YJ MODELS
On YJ models, the PCM is located in the engine
compartment behind the windshield washer fluid res-
ervoir (Fig. 18).
REMOVAL
(1) Disconnect negative battery cable at battery.
(2) Remove windshield washer fluid reservoir.
(3) Loosen 60-way connector mounting screw until
connector can be disengaged from PCM.
(4) Pull 60-way connector straight back from PCM.
(5) Remove PCM mounting bolts.
(6) Remove PCM from vehicle.
INSTALLATION
(1) Check the pins in the PCM 60-way electrical
connector for damage. Repair as necessary.
(2) Install PCM. Tighten mounting bolts to 1 Nzm
(9 in. lbs.) torque.
(3) Engage 60-way connector into PCM. Tighten
connector mounting screw to 4 Nzm (35 in. lbs.)
torque.
(4) Connect battery cable to battery.
(5) Install washer fluid reservoir.
SPARK PLUGS
PLUG REMOVAL
(1) Always remove spark plug or ignition coil ca-
bles by grasping at the cable boot (Fig. 19). Turn the
cable boot 1/2 turn and pull straight back in a steady
Fig. 17 PCM LocationÐXJ Models
Fig. 18 PCM LocationÐYJ Models
JIGNITION SYSTEMS 8D - 23