1995 JEEP YJ oil reset

The gauge needle moves as the movable permanent
magnet aligns itself to the changing magnetic fields
created around it by the electromagnets.
COOLANT TEMPERATURE GAUGE
The coolant temperature gauge gives an indication
of engine coolant temperature. The coolant tempera-
ture sending unit is a thermistor that changes elec-
trical resistance with changes in engine coolant
temperature. High sending unit resistance causes
low coolant temperature readings. Low resistance
causes high coolant temperature readings. Sending
unit resistance values are shown in a chart in Spec-
ifications.
FUEL GAUGE
The fuel gauge gives an indication of the level of
fuel in the fuel tank. The fuel gauge sending unit has
a float attached to a swing-arm in the fuel tank. The
float moves up or down within the fuel tank as fuel
level changes. As the float moves, an electrical con-
tact on the swing-arm wipes across a resistor coil,
which changes sending unit resistance. High sending
unit resistance causes high fuel level readings. Low
resistance causes low fuel level readings. Sending
unit resistance values are shown in a chart in Spec-
ifications.
OIL PRESSURE GAUGE
The oil pressure gauge gives an indication of en-
gine oil pressure. The combination oil pressure send-
ing unit contains a flexible diaphragm. The
diaphragm moves in response to changes in engine
oil pressure. As the diaphragm moves, sending unit
resistance increases or decreases. High resistance on
the gauge side of the sending unit causes high oil
pressure readings. Low resistance causes low oil
pressure readings. Sending unit resistance values are
shown in a chart in Specifications.
SPEEDOMETER/ODOMETER
The speedometer/odometer give an indication of ve-
hicle speed and travel distance. The speedometer re-
ceives a vehicle speed pulse signal from the Vehicle
Speed Sensor (VSS). An electronic integrated circuit
contained within the speedometer reads and analyzes
the pulse signal. It then adjusts the ground path re-
sistance of one electromagnet in the gauge to control
needle movement. It also sends signals to an electric
stepper motor to control movement of the odometer
number rolls. Frequency values for the pulse signal
are shown in a chart in Specifications.
The VSS is mounted to an adapter near the trans-
fer case output shaft. The sensor is driven through
the adapter by a speedometer pinion gear. The
adapter and pinion vary with transmission, axle ratio
and tire size. Refer to Group 21 - Transmission and
Transfer Case for more information.
TACHOMETER
The tachometer gives an indication of engine speed
in Revolutions-Per-Minute (RPM). With the engine
running, the tachometer receives an engine speed
pulse signal from the Powertrain Control Module
(PCM). An electronic integrated circuit contained
within the tachometer reads and analyzes the pulse
signal. It then adjusts the ground path resistance of
one electromagnet in the gauge to control needle
movement. Frequency values for the pulse signal are
shown in a chart in Specifications.
TRIP ODOMETER
The trip odometer is driven by the same electronic
integrated circuit as the speedometer/odometer. How-
ever, by depressing the trip odometer reset knob on
the face of the speedometer, the trip odometer can be
reset to zero. The trip odometer is serviced only as a
part of the speedometer/odometer gauge assembly.
VOLTMETER
The voltmeter is connected in parallel with the bat-
tery. With the ignition switch ON, the voltmeter in-
dicates battery or generator output voltage,
whichever is greater.
INDICATOR LAMPS
All indicator lamps, except the four-wheel drive in-
dicator, are located in the main cluster tell-tale area
above the steering column opening. Each of the
lamps is served by the main cluster printed circuit
and cluster connector. The four-wheel drive indicator
lamp is located in the gauge package cluster and is
served by the gauge package printed circuit and clus-
ter connector.
Up to eleven indicator lamps can be found in the
tell-tale area of the main cluster. These lamps are ar-
ranged in two rows, with six lamps in the upper row
and five lamps in the lower row.
ANTI-LOCK BRAKE SYSTEM LAMP
The Anti-Lock Brake System (ABS) lamp is
switched to ground by the ABS module. The module
lights the lamp when the ignition switch is turned to
the START position as a bulb test. The lamp will
stay on for 3 to 5 seconds after vehicle start-up to in-
dicate a system self-test is in process. If the lamp re-
mains on after start-up, or comes on and stays on
while driving, it may indicate that the ABS module
has detected a system malfunction or that the system
has become inoperative. Refer to Group 5 - Brakes
for more information.
BRAKE WARNING LAMP
The brake warning lamp warns the driver that the
parking brake is applied or that the pressures in the
two halves of the split brake hydraulic system are
unequal. With the ignition switch turned ON, battery
JINSTRUMENT PANEL AND GAUGESÐYJ 8E - 25

AUDIO SYSTEMS
CONTENTS
page page
DIAGNOSIS............................. 2
GENERAL INFORMATION.................. 1SERVICE PROCEDURES................... 6
GENERAL INFORMATION
Following are general descriptions of major compo-
nents used in XJ (Cherokee)/YJ (Wrangler) audio sys-
tems. Refer to Group 8W - Wiring Diagrams for
complete circuit descriptions and diagrams.
RADIOS
Radio options for the XJ and YJ models include an
AM/FM stereo or an AM/FM stereo/cassette receiver.
Both units are Electronically-Tuned Radios (ETR)
and include a clock function. For more information
on radio features, setting procedures, and control
functions refer to the owner's manual.
IN-LINE FUSE
Each radio receives fused battery feed when the ig-
nition switch is in the ON or ACCESSORY position.
There is an additional in-line fuse in the back of the
radio chassis. The in-line fuse (Fig. 1) will blow to
protect the vehicle electrical system in the event of
internal radio failure.
IGNITION-OFF DRAW FUSE
All vehicles are equipped with an Ignition-Off
Draw (IOD) fuse that is removed when the vehicle is
shipped from the factory. This fuse feeds various ac-
cessories that require current when the ignition
switch is in the OFF position, including the clock and
radio station preset memory functions. The fuse is re-
moved to prevent battery discharge during vehicle
storage.The IOD fuse should be checked if the radio station
preset memory or clock functions are erratic or inop-
erative. The IOD fuse is located in the Power Distri-
bution Center (PDC). Refer to underside of PDC
cover for IOD fuse identification.
RADIO ILLUMINATION RELAY
All radios are connected to a radio illumination re-
lay. The relay controls the source of battery feed for
radio/clock display illumination.
When the park and headlamp switch is in the OFF
position, the radio illumination relay remains de-en-
ergized. The radio/clock display receives full battery
voltage through the normally closed contacts of the
relay. This results in the radio/clock display being il-
luminated at full brightness for easier visibility in
daylight.
When the park and headlamp switch is in the ON
position, the radio illumination relay coil is ener-
gized. With the relay coil energized, the normally
closed contacts of the relay open, and the normally
open contacts of the relay close. This causes the ra-
dio/clock display to receive battery feed through the
instrument panel dimmer switch. The display illumi-
nation brightness can now be adjusted with other
panel lamps for night visibility.
SPEAKERS
Speaker system options include two, four or six (XJ
only) speaker locations. On XJ model two-speaker
systems, one speaker is located in each front door.
Four-speaker systems add one speaker at each end of
a rear-mounted overhead sound bar. The premium
six-speaker option upgrades all the speakers in the
above locations, and adds one tweeter at each end of
the lower instrument panel.
On YJ model two-speaker systems, one speaker is
located at each end of the instrument panel. Four-
speaker systems add one speaker at each end of a
rear-mounted overhead sound bar.
Fig. 1 In-Line Fuse
JAUDIO SYSTEMS 8F - 1

SIDE CLEARANCE MEASUREMENT
Slide snug-fitting feeler gauge between the connect-
ing rod and crankshaft journal flange. Refer to En-
gine Specifications for the proper clearance. Replace
the connecting rod if the side clearance is not within
specification.
PISTON FITTING
BORE GAUGE METHOD
(1) To correctly select the proper size piston, a cyl-
inder bore gauge, Special Tool 6879 or equivalent, ca-
pable of reading in .00019INCREMENTS with gauge
ring Special Tool 6884 is required. If a bore gauge is
not available, do not use an inside micrometer.
(2) Set the bore gauge to the gauge ring and zero
gauge.
(3) Remove gauge from ring and check cylinder as
shown in (Fig. 8) bore and record reading.
(4) Measure the inside diameter of the cylinder
bore at a point 58.725 mm (2-5/16 inches) below top
of bore. Start perpendicular (across or at 90 degrees)
to the axis of the crankshaft at point B and then take
an additional bore reading 90 degrees to that at point A.
(5) Recheck bore gauge in gauge ring, bore gauge
should read zero. If gauge does not read zero, reset
gauge and start over with procedure.
The coated pistons will be serviced with the piston
pin and connecting rod pre-assembled.The coated
piston connecting rod assembly can be used to
service previous built engines and MUST be re-
placed as complete sets.Tin coated pistons should
not be used as replacements for the new coated pistons.
The coating material is applied to the piston after
the final piston machining process. Measuring the
outside diameter of a coated piston will not provide
accurate results. Therefore, measuring the inside di-
ameter of the cylinder bore with a dial Bore Gauge is
MANDATORY. To correctly select the proper size
piston, a cylinder bore gauge capable of reading in.00019increments is required.
Piston installation into the cylinder bore requires
slightly more pressure than that required for non-
coated pistons. The bonded coating on the piston will
give the appearance of a line-to-line fit with the cyl-
inder bore.
PISTON PIN
Piston pins are press-fitted into the connecting rods
and require no locking device. The piston, piston pin
and connecting rod are replaced as an assembly.
PISTON RING FITTING
(1) Carefully clean the carbon from all ring
grooves. Oil drain openings in the oil ring groove and
pin boss must be clear. DO NOT remove metal from
the grooves or lands. This will change ring-to-groove
clearances and will damage the ring-to-land seating.
(2) Be sure the piston ring grooves are free of nicks
and burrs.
(3) Measure the ring side clearance with a feeler
gauge fitted snugly between the ring land and ring
(Fig. 10). Rotate the ring in the groove. It must move
freely around circumference of the groove.
(4) Place ring in the cylinder bore and push down
with inverted piston to position near lower end of the
ring travel. Measure ring gap with a feeler gauge fit-
ting snugly between ring ends (Fig. 12). The correct
compression ring end gap is 0.25-0.51 mm (0.010-
0.020 inch). The correct oil control ring end gap is
0.381-1.397 mm (0.015-0.055 inch).
Fig. 8 Bore Gauge
Fig. 9 Piston Size Chart
Fig. 10 Piston Dimensions
9 - 42 2.5L ENGINEJ

SIDE CLEARANCE MEASUREMENT
Slide snug-fitting feeler gauge between the connect-
ing rod and crankshaft journal flange. Refer to En-
gine Specifications for the proper clearance. Replace
the connecting rod if the side clearance is not within
specification.
PISTON FITTING
BORE GAUGE METHOD
(1) To correctly select the proper size piston, a cyl-
inder bore gauge, Special Tool 6879 or equivalent, ca-
pable of reading in .00019INCREMENTS with gauge
ring Special Tool 6884 is required. If a bore gauge is
not available, do not use an inside micrometer.
(2) Set the bore gauge to the gauge ring and zero
gauge.
(3) Remove gauge from ring and check cylinder as
shown in (Fig. 8) bore and record reading.
(4) Measure the inside diameter of the cylinder
bore at a point 58.725 mm (2-5/16 inches) below top
of bore. Start perpendicular (across or at 90 degrees)
to the axis of the crankshaft at point B and then take
an additional bore reading 90 degrees to that at point A.
(5) Recheck bore gauge in gauge ring, bore gauge
should read zero. If gauge does not read zero, reset
gauge and start over with procedure.
The coated pistons will be serviced with the piston
pin and connecting rod pre-assembled.The coated
piston connecting rod assembly can be used to
service previous built engines and MUST be re-
placed as complete sets.Tin coated pistons should
not be used as replacements for the new coated pistons.
The coating material is applied to the piston after
the final piston machining process. Measuring the
outside diameter of a coated piston will not provide
accurate results. Therefore, measuring the inside di-
ameter of the cylinder bore with a dial Bore Gauge is
MANDATORY. To correctly select the proper sizepiston, a cylinder bore gauge capable of reading
.00019increments is required.
Piston installation into the cylinder bore requires
slightly more pressure than that required for non-
coated pistons. The bonded coating on the piston will
give the appearance of a line-to-line fit with the cyl-
inder bore.
PISTON PIN
Piston pins are press-fitted into the connecting rods
and require no locking device. The piston, piston pin
and connecting rod are replaced as an assembly.
PISTON RING FITTING
(1) Carefully clean the carbon from all ring
grooves. Oil drain openings in the oil ring groove and
pin boss must be clear. DO NOT remove metal from
the grooves or lands. This will change ring-to-groove
clearances and will damage the ring-to-land seating.
(2) Be sure the piston ring grooves are free of nicks
and burrs.
(3) Measure the ring side clearance with a feeler
gauge fitted snugly between the ring land and ring
(Fig. 11). Rotate the ring in the groove. It must move
freely around circumference of the groove.
(4) Place ring in the cylinder bore and push down
with inverted piston to position near lower end of the
ring travel. Measure ring gap with a feeler gauge fit-
ting snugly between ring ends (Fig. 12). The correct
compression ring end gap is 0.25-0.51 mm (0.010-
0.020 inch). The correct oil control ring end gap is
0.381-1.397 mm (0.015-0.055 inch).
Fig. 8 Bore Gauge
Fig. 9 Piston Size Chart
Fig. 10 Piston Dimensions
9 - 84 4.0L ENGINEJ