1995 JEEP CHEROKEE Service Repair Manual

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Page 313 of 2198

JEEP CHEROKEE 1995 Service Repair Manual CAMSHAFT POSITION SENSOR
The camshaft position sensor is located in the dis-
tributor (Figs. 3 or 4) on all engines.The camshaft position sensor contains a hall effect
device called a sync signal gene

Page 314 of 2198

JEEP CHEROKEE 1995 Service Repair Manual CRANKSHAFT POSITION SENSOR
The crankshaft position sensor is mounted to the
transmission bellhousing at the left/rear side of the
engine block (Figs. 5, 6 or 7).
Engine speed and crankshaft position a

Page 315 of 2198

JEEP CHEROKEE 1995 Service Repair Manual groups of four pulses generated on 2.5L 4-cylinder
engines. There are 3 groups of four pulses generated
on 4.0L 6-cylinder engines.
The trailing edge of the fourth notch, which causes
the pulse, is fo

groups of four pulses generated on 2.5L 4-cylinder
engines. There are 3 groups of four pulses generated
on 4.0L 6-cylinder engines.
The trailing edge of the fourth notch, which causes
the pulse, is four degrees before top dead center
(TDC) of the corresponding piston.
The engine will not operate if the PCM does not re-
ceive a crankshaft position sensor input.
For component testing, refer to the Diagnostics/Ser-
vice Procedures section of this group.
For removal and installation of this sensor, refer to
the Component Removal/Installation section of this
group.
DISTRIBUTORS
All engines are equipped with a camshaft driven
mechanical distributor containing a shaft driven dis-
tributor rotor. All distributors are equipped with an
internal camshaft position (fuel sync) sensor. This
sensor provides fuel injection synchronization and
cylinder identification.
The distributors on both the 2.5L 4-cylinder and
the 4.0L-6 cylinder engines do not have built in cen-
trifugal or vacuum assisted advance. Base ignition
timing and all timing advance is controlled by the
powertrain control module (PCM). Because ignition
timing is controlled by the PCM,base ignition tim-
ing is not adjustable on any of these engines.
The distributor is locked in place by a fork with a
slot located on the distributor housing base. The dis-
tributor holddown clamp bolt passes through this slot
when installed. Because the distributor position is
locked when installed, its rotational position can not
be changed.Do not attempt to modify the dis-tributor housing to get distributor rotation.
Distributor position will have no effect on igni-
tion timing. The position of the distributor will
determine fuel synchronization only.
All distributors contain an internal oil seal that
prevents oil from entering the distributor housing.
The seal is not serviceable.
Distributor removal and installation procedures
have changed for the 1995 model year. Refer to Dis-
tributor in the Component Removal/Installation sec-
tion of this group.
IGNITION COIL
Battery voltage is supplied to the ignition coil pos-
itive terminal from the ASD relay.
The powertrain control module (PCM) opens and
closes the ignition coil ground circuit for ignition coil
operation. This is done through pin/cavity number 19
of the PCM 60-way connector.
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 ad-
vance. This is done to meet changing engine operat-
ing 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.
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).
Fig. 9 Sensor OperationÐ4.0L 6-Cyl. EngineÐAll
Except YJ Models With Automatic Transmission
Fig. 10 Sensor OperationÐ4.0L 6-Cyl. EngineÐYJ
Models With Automatic Transmission
8D - 4 IGNITION SYSTEMSJ

Page 316 of 2198

JEEP CHEROKEE 1995 Service Repair Manual 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. 11).
For component testing, refer to the Diagnostics/Ser-
vic

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. 11).
For component testing, refer to the Diagnostics/Ser-
vice Procedures section of this group.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
ENGINE COOLANT TEMPERATURE SENSOR
For an operational description, diagnosis and re-
moval/installation procedures, refer to Group 14,
Fuel System.
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.
POWERTRAIN CONTROL MODULE (PCM)
The PCM was formerly referred to as the SBEC or
engine controller. On XJ models, the PCM is located
in the engine compartment next to the air cleaner
(Fig. 12). On YJ models, the PCM is located in the
engine compartment behind the windshield washer
fluid reservoir (Fig. 13).
The ignition system is controlled by the PCM.
Base ignition timing by rotation of distributor
is not adjustable.The PCM opens and closes the ig-
nition coil ground circuit to operate the ignition coil.
This is done to adjust ignition timing, both initial
(base) and advance, for changing engine operating
conditions.The amount of electronic spark advance provided
by the PCM is determined by five input factors: En-
gine coolant temperature, engine rpm, intake mani-
fold air temperature, intake manifold absolute
pressure and throttle position.
For removal and installation of this component, re-
fer to the Component Removal/Installation section of
this group.
For PCM diagnostics, refer to the appropriate Pow-
ertrain Diagnostic Procedures service manual for op-
eration of the DRB scan tool.
THROTTLE POSITION 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 and re-
moval/installation procedures, refer to Group 14,
Fuel System.
Fig. 11 Ignition CoilÐTypical
Fig. 12 PCM LocationÐXJ Models
Fig. 13 PCM LocationÐYJ Models
JIGNITION SYSTEMS 8D - 5

Page 317 of 2198

JEEP CHEROKEE 1995 Service Repair Manual DIAGNOSTICS/SERVICE PROCEDURES
INDEX
page page
Automatic Shutdown (ASD) Relay Test.......... 6
Camshaft Position Sensor Test................ 6
Crankshaft Position Sensor Test............... 7
Distribu

DIAGNOSTICS/SERVICE PROCEDURES
INDEX
page page
Automatic Shutdown (ASD) Relay Test.......... 6
Camshaft Position Sensor Test................ 6
Crankshaft Position Sensor Test............... 7
Distributor Cap............................ 7
Distributor Rotor........................... 8
DRB Scan Tool............................ 8
Engine Coolant Temperature Sensor Test........ 9
General Information........................ 6
Ignition Coil.............................. 9
Ignition Secondary Circuit Diagnosis........... 10Ignition Timing............................ 11
Intake Manifold Air Temperature Sensor Test..... 11
Manifold Absolute Pressure (MAP) Sensor Test . . . 11
On-Board Diagnostics...................... 15
Oxygen (O2S) Sensor Tests................. 15
Powertrain Control Module (PCM)............. 11
Spark Plug Secondary Cables................ 14
Spark Plugs............................. 12
Throttle Position Sensor Test................. 15
GENERAL INFORMATION
This section of the group, Diagnostics/Service Pro-
cedures, will discuss basic ignition system diagnostics
and service adjustments.
For system operation and component identification,
refer to the Component Identification/System Opera-
tion section of this group.
For removal or installation of ignition system com-
ponents, refer to the Component Removal/Installa-
tion section of this group.
For other useful information, refer to the On-Board
Diagnostics section.
For operation of the DRB Scan Tool, refer to the
appropriate Powertrain Diagnostic Procedures ser-
vice manual.
AUTOMATIC SHUTDOWN (ASD) RELAY TEST
To perform a complete test of this relay and its cir-
cuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the relay only, refer to RelaysÐOpera-
tion/Testing in the Group 14, Fuel Systems section.
CAMSHAFT POSITION SENSOR TEST
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the sensor only, refer to the following:
The camshaft position sensor is located in the dis-
tributor (Fig. 1).
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the sensor only, refer to the following:
For this test, an analog (non-digital) voltme-
ter is needed.Do not remove the distributor connec-
tor from the distributor. Using small paper clips,
insert them into the backside of the distributor wire
harness connector to make contact with the termi-nals. Be sure that the connector is not damaged
when inserting the paper clips. Attach voltmeter
leads to these paper clips.
(1) Connect the positive (+) voltmeter lead into the
sensor output wire. This is at done the distributor
wire harness connector. For wire identification, refer
to Group 8W, Wiring Diagrams.
(2) Connect the negative (-) voltmeter lead into the
ground wire. For wire identification, refer to Group
8W, Wiring Diagrams.
(3) Set the voltmeter to the 15 Volt DC scale.
(4) Remove distributor cap from distributor (two
screws). Rotate (crank) the engine until the distribu-
tor rotor is pointed to approximately the 11 o'clock
position. The movable pulse ring should now be
within the sensor pickup.
(5) Turn ignition key to ON position. The voltmeter
should read approximately 5.0 volts.
(6) If voltage is not present, check the voltmeter
leads for a good connection.
(7) If voltage is still not present, check for voltage
at the supply wire. For wire identification, refer to
Group 8W, Wiring Diagrams.
Fig. 1 Camshaft Position SensorÐTypical
8D - 6 IGNITION SYSTEMSJ

Page 318 of 2198

JEEP CHEROKEE 1995 Service Repair Manual (8) If voltage is not present at supply wire, check
for voltage at pin-7 of powertrain control module
(PCM) 60-way connector. Leave the PCM connector
connected for this test.
(9) If voltage is still n

(8) If voltage is not present at supply wire, check
for voltage at pin-7 of powertrain control module
(PCM) 60-way connector. Leave the PCM connector
connected for this test.
(9) If voltage is still not present, perform vehicle
test using the DRB scan tool.
(10) If voltage is present at pin-7, but not at the
supply wire:
(a) Check continuity between the supply wire.
This is checked between the distributor connector
and pin-7 at the PCM. If continuity is not present,
repair the harness as necessary.
(b) Check for continuity between the camshaft
position sensor output wire and pin-44 at the PCM.
If continuity is not present, repair the harness as
necessary.
(c) Check for continuity between the ground cir-
cuit wire at the distributor connector and ground.
If continuity is not present, repair the harness as
necessary.
(11) While observing the voltmeter, crank the en-
gine with ignition switch. The voltmeter needle
should fluctuate between 0 and 5 volts while the en-
gine is cranking. This verifies that the camshaft po-
sition sensor in the distributor is operating properly
and a sync pulse signal is being generated.
If sync pulse signal is not present, replacement of
the camshaft position sensor is necessary.
For removal or installation of ignition system com-
ponents, refer to the Component Removal/Installa-
tion section of this group.
For system operation and component identification,
refer to the Component Identification/System Opera-
tion section of this group.
CRANKSHAFT POSITION SENSOR TEST
To perform a complete test of this sensor and its
circuitry, refer to the DRB scan tool. Also refer to the
appropriate Powertrain Diagnostics Procedures man-
ual. To test the sensor only, refer to the following:
The sensor is located on the transmission bellhous-
ing at the left/rear side of the engine block (Figs. 2, 3
or 4).
(1) Near the rear of the intake manifold, discon-
nect sensor pigtail harness connector from main wir-
ing harness.
(2) Place an ohmmeter across terminals B and C
(Fig. 5). Ohmmeter should be set to 1K-to-10K scale
for this test. The meter reading should be open (no
resistance). Replace sensor if a low resistance is indi-
cated.
For removal or installation of ignition system com-
ponents, refer to the Component Removal/Installa-
tion section of this group.DISTRIBUTOR CAP
INSPECTION
Remove the distributor cap and wipe it clean with
a dry lint free cloth. Visually inspect the cap for
cracks, carbon paths, broken towers, or damaged ro-
tor button (Figs. 6 and 7). Also check for white depos-
its on the inside (caused by condensation entering
the cap through cracks). Replace any cap that dis-
plays charred or eroded terminals. The inside flat
surface of a terminal end (faces toward rotor) will in-
dicate some evidence of erosion from normal opera-
tion. Examine the terminal ends for evidence of
mechanical interference with the rotor tip.
If replacement of the distributor cap is necessary,
transfer spark plug cables from the original cap to
the new cap. This should be done one cable at a time.
Each cable is installed onto the tower of the new cap
that corresponds to its tower position on the original
Fig. 2 Crankshaft Position SensorÐ2.5L 4-Cyl.
EngineÐTypical
Fig. 3 Crankshaft Position SensorÐ4.0L 6-Cyl.
EngineÐAll Except YJ models With Auto. Trans.
JIGNITION SYSTEMS 8D - 7

Page 319 of 2198

JEEP CHEROKEE 1995 Service Repair Manual cap. Fully seat the cables onto the towers. If neces-
sary, refer to the engine Firing Order diagrams (Figs.
8or9).
DISTRIBUTOR ROTOR
Visually inspect the rotor (Fig. 10) for cracks, evi-
dence of cor

Page 320 of 2198

JEEP CHEROKEE 1995 Service Repair Manual IGNITION COIL
To perform a complete test of the ignition coil and
its circuitry, refer to the DRB scan tool. Also refer tothe appropriate Powertrain Diagnostics Procedures
manual. To test the coil onl

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