2002 JEEP LIBERTY Battery circuit

(1) Remove the trailer tow relay from the connec-
tor bank. (Refer to 8 - ELECTRICAL/LAMPS/LIGHT-
ING - EXTERIOR/TRAILER TOW RELAY -
REMOVAL).
(2) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 3. If not OK, replace the faulty relay.
(3) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   8 ohms. If OK, go to Step
4. If not OK, replace the faulty relay.
(4) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, test the input and output circuits of
the relay. Refer to the appropriate wiring informa-
tion.
REMOVAL
The trailer tow relay bank contains four relays.
The service procedures for each relay are the same.
Be certain any removed relay is replaced with the
same relay size and type that was removed.
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, THENWAIT 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) Disconnect and isolate the battery negative
cable.
(2) Remove the trim from the right side quarter
inner panel. (Refer to 23 - BODY/INTERIOR/QUAR-
TER TRIM PANEL - REMOVAL).
(3) Reach through the access hole in the quarter
inner panel behind the right rear wheelhouse to
locate and retrieve the trailer tow relay connector
bank, which is enveloped in foam rubber and placed
on the top of the right rear wheelhouse between the
quarter inner and outer panels (Fig. 66).
(4) Pull the trailer tow relay connector bank into
the cargo area far enough to access the unit for ser-
vice.
(5) Carefully remove the trailer tow relay connec-
tor bank from the foam wrap.
(6) Remove the trailer tow relay by grasping it
firmly and pulling it straight out from the connector
bank (Fig. 67).
INSTALLATION
The trailer tow relay bank contains four relays.
The service procedures for each relay are the same.
Be certain any removed relay is replaced with the
same relay size and type that was removed.
Fig. 65 ISO Micro Relay
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
Fig. 66 Trailer Tow Relay Wrap
1 - FOAM WRAP
2 - REAR BODY WIRE HARNESS
KJLAMPS8Ls-63
TRAILER TOW RELAY (Continued)

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 trailer tow relay to the proper con-
nector in the connector bank (Fig. 67).
(2) Align the trailer tow relay terminals with the
terminal cavities in the connector.
(3) Push firmly and evenly on the top of the trailer
tow relay until the terminals are fully seated in the
terminal cavities in the connector.
(4) Carefully restore the foam wrap around the
trailer tow relay connector bank (Fig. 66).
(5) Reach through the access hole in the quarter
inner panel behind the right rear wheelhouse to
place the trailer tow relay connector bank on the top
of the right rear wheelhouse between the quarter
inner and outer panels.(6) Reinstall the trim onto the right side quarter
inner panel. (Refer to 23 - BODY/INTERIOR/QUAR-
TER TRIM PANEL - INSTALLATION).
(7) Reconnect the battery negative cable.
TRAILER TOW WIRING
DESCRIPTION
Vehicles equipped with an optional factory-in-
stalled (not dealer-installed or port-installed) trailer
towing package have a rear body wire harness that
includes an integral trailer tow wiring take out that
connects to a heavy duty, sealed, 7-pin trailer tow
connector located on a bracket on the trailer hitch
receiver (Fig. 68). This harness includes a second
take out with a trailer tow relay connector bank and
four trailer tow relays that isolate the right turn sig-
nal, left turn signal, and brake lamp circuits of the
vehicle from the electrical system of the trailer. The
fourth relay in the connector bank provides a fused
ignition switch output (run) source of battery current
to the trailer tow connector through a trailer tow
relay output circuit. The package also includes an
adapter harness (stored beneath the left rear seat
cushion of the vehicle when it is shipped from the
factory) that adapts the 7-pin trailer tow connector to
a standard, light-duty, 4-pin trailer tow connector.
Refer to the appropriate wiring information. The wir-
ing information includes wiring diagrams, proper
wire and connector repair procedures, further details
on wire harness routing and retention, as well as
pin-out and location views for the various wire har-
ness connectors, splices and grounds.
Fig. 67 Trailer Tow Relay Remove/Install
1 - RELAY CONNECTOR BANK
2 - REAR BODY WIRE HARNESS
3 - LEFT TURN RELAY
4 - RIGHT TURN RELAY
5 - BRAKE LAMP RELAY
6 - FUSED IGNITION SWITCH OUTPUT (RUN) RELAY
Fig. 68 Trailer Tow Wiring
1 - RETAINER CLIP (4)
2 - REAR BODY HARNESS (TRAILER TOW TAKE OUT)
3 - RETAINER CLIP (2)
4 - WIRE HARNESS CONNECTOR
8Ls - 64 LAMPSKJ
TRAILER TOW RELAY (Continued)

LAMP BAR
DESCRIPTION
The lamp bar is used to better illuminate the driv-
ers field of vision under certain driving conditions. It
consists of a cover, two or four lamp assemblies
(depending upon which market), and a wiring har-
ness. These components are mounted to a reinforce-
ment, then sealed and secured to the roof panel.
Lamp bar illumination is controlled by a manually
operated momentary rocker switch, mounted to the
instrument panel. The lamps are adjustable in the
vertical position only.
OPERATION
Battery and ignition voltage are supplied to the
lamp bar switch assembly. When the switch is in the
on position the internal relay contacts close, complet-
ing the circuit through the lamp bar bulbs, to
ground. The lamp bar assembly is grounded to the
chassis. The hard wired circuits of the lamp bar may
be diagnosed and tested using conventional methods
and procedures.
DIAGNOSIS AND TESTING - LAMP BAR
CONDITION POSSIBLE CAUSES CORRECTION
LAMP BAR LAMPS
INOPERATIVEFaulty or missing fuse Test and replace lamp bar fuse
as required
Faulty feed circuit Test and repair open battery or
ignition feed circuit.
Faulty ground circuit Test and repair high resistance
or open lamp bar ground circuit
Faulty lamp bar sense circuit Test and repair short to voltage
in lamp bar sense circuit
Faulty switch Test and replace lamp bar
switch
LAMP BAR LAMPS ON AT
ALL TIMESFaulty switch Test and replace lamp bar
switch
Lamp bar feed circuit Test and repair short to voltage
in lamp bar feed circuit
ONE OR MORE LAMPS
INOPERATIVEFaulty or missing bulb Test and repair lamp bar lamp
bulb(s) as required
Faulty lamp bar wiring harness Test and repair short/open lamp
bar wiring harness
STANDARD PROCEDURE - LAMP BAR AIMING
NOTE: The lamp bar lamps are adjustable to the
vertical position only.
(1) Remove lamp bar cover.
(2) Using a fairly dark and level area, drive the
vehicle perpendicular to and 25 ft. away from a wall.
(3) Measure up the wall 7ft. 9in. and place tape on
the wall parallel to the ground.
(4) Turn on the lamp bar lamps.
(5) Using the adjustment screw in the rear of each
lamp, adjust the lamp beam to the center of the tape.
REMOVAL
REMOVAL - LAMP BAR
(1) Disconnect the negative battery cable.
(2) Remove the lamp bar cover retaining screws,
slide the cover forward and up to remove.
(3) Disconnect lamp electrical connector.
(4) Remove the lamp bar reinforcement to roof
stud retainers.
CAUTION: The reinforcement is held to the roof by
protective tape. Remove the tape carefully to pre-
vent damage to roof panel. After removal, the area
must be cleaned with the appropriate solvent.
KJLAMPS8Ls-65

LAMP BAR SWITCH
DESCRIPTION
The lamp bar switch is intended to close the elec-
trical circuit which feeds the lamp bar. The switch
assembly contains a relay unit that is energized or
de-energized by a manually operated momentary
rocker switch. The switch is mounted on the instru-
ment panel left of the steering wheel.
REMOVAL
CAUTION: Care must be taken not to damage the
dash or instrument panel when removing the lamp
bar switch bezel.
(1) Disconnect negative battery cable.
(2) Using a suitable pry tool, carefully remove the
lamp bar switch bezel from the instrument panel.
(3) Disconnect the electrical connector.
(4) Depress the lamp bar switch retaining tabs and
remove the switch from the bezel.
INSTALLATION
(1) Press the lamp bar switch into the instrument
panel bezel and assure that the switch is seated
properly (Fig. 70).
(2) Connect the electrical connector.
(3) Press the instrument panel bezel into position
and seat the bezal retaining clips.(4) Reconnect negative battery cable.
Fig. 70 LAMP BAR SWITCH
1 - Bezel
2 - Lamp Bar Switch
KJLAMPS8Ls-67

²STEP
²C/T - Compass/Temperature
²US/M - English/Metric
²RESET
1. STEP BUTTON
Pressing the STEP button selects one of the follow-
ing 6 displays:
²Average fuel economy
²Distance to empty
²Instantaneous fuel economy
²Trip odometer
²Elapsed time
²Blank Screen
2. C/T (COMPASS/TEMPERATURE)
BUTTON
Pressing the C/T button selects the Compass/Tem-
perature display.
3. US/M (ENGLISH/METRIC
MEASUREMENT) BUTTON
Pressing the US/M button switches the display
units between English and Metric readings.
4. RESET BUTTON
Pressing the RESET button resets the function on
the display, provided that function can be reset. The
functions which can be reset are Average fuel econ-
omy, Trip odometer and Elapsed time.
Global ResetThis feature allows all three dis-
plays (Average fuel economy, Trip odometer and
Elapsed time) to be reset easily, by pressing the
RESET button twice within three seconds with any
of the screens in display. This eliminates the need to
reset each display individually.
The RESET button is also used to set the variance
and/or calibrate the compass. Refer to the Variance
Procedure and Calibration Procedure in this section.
For more information on the features, control func-
tions and setting procedures for the CMTC module,
see the owner's manual in the vehicle glove box.
DIAGNOSIS AND TESTING - COMPASS
MINI-TRIP COMPUTER
The following diagnostic procedure can be used if
the compass mini-trip computer is not operational in
any way. If the problem is specific to a individual
CMTC display, go to the appropriate display title
noted below and diagnose using the information pro-
vided on how these displays are generated.
(1) Remove the overhead console from the head-
liner (Refer to 8 - ELECTRICAL/OVERHEAD CON-
SOLE - REMOVAL).
(2) Using a ohmmeter, check the ground circuit
cavity of the compass mini-trip computer electricalconnector for proper continuity to ground. Continuity
should be present, If OK go to Step 3, If not OK
repair the open or shorted ground circuit as required.
NOTE: Connect the negative battery cable before
proceeding.
(3) Using a voltmeter, check the fused (B+) circuit
cavity of the compass mini-trip computer electrical
connector for 12v. Voltage should be present, If OK go
to Step 4, If not OK repair the open or shorted fused
(B+) circuit as required.
(4) Using a voltmeter, check the fused ignition
switch output circuit cavity of the compass mini-trip
computer electrical connector for 12v with Key ON.
Voltage should be present, If OK, replace the inoper-
ative CMTC module, If not OK repair the open or
shorted fused ignition switch output circuit as
required.
TEMPERATURE
The compass mini-trip computer receives Program-
mable Communications Interface bus (PCI bus) mes-
sages from the Body Control Module (BCM) for all
displayed information except the compass display. If
a dash (-) is displayed, the compass mini-trip com-
puter is not receiving a PCI bus message from the
BCM. To check out the PCI bus line and the BCM,
use the DRB llltscan tool and proper Body Diagnos-
tic Procedure Manual.
If the compass mini-trip computer displays a tem-
perature more than 54É C (130É F), check for a short
circuit between the temperature sensor and the
BCM.
If the compass mini-trip computer displays a tem-
perature less than -40É C (-67É F), check for an open
circuit between the temperature sensor and the
BCM.
AVERAGE FUEL ECONOMY
The compass mini-trip computer receives average
fuel economy information from the BCM over the PCI
bus line. If the compass mini-trip computer displays
-.- instead of an average fuel economy value, it is not
receiving a PCI bus message for the average fuel
economy from the BCM. To check out the PCI bus
line and the BCM use the DRB llltscan tool and
proper Body Diagnostic Procedure Manual.
DISTANCE TO EMPTY
The compass mini-trip computer receives distance
to empty information from the BCM over the PCI bus
line. If compass mini-trip computer displays a dash
(-) instead of a distance to empty value, it is not
receiving a PCI bus message for the distance to
empty from the BCM. To check out the PCI bus line
8M - 6 MESSAGE SYSTEMSKJ
COMPASS/MINI-TRIP COMPUTER (Continued)

(3) Remove the compass mini-trip computer from
the overhead console.
INSTALLATION
(1) Install the compass mini-trip computer in the
overhead console. Align the compass mini-trip com-
puter guides on the housing with the grooves of the
console.
(2) Install the mounting screws and install the
map lamp wire connector on the compass mini-trip
computer. Make sure the LOOP of wire that was
clipped into the compass mini-trip computer module
housing is properly clipped into the new module
before the console is placed back into the headliner.
(3) Install the overhead console, refer to Console
Installation in this section.
UNIVERSAL TRANSMITTER
DESCRIPTION
On some KJ models a Universal Transmitter trans-
ceiver is standard factory-installed equipment. The
universal transmitter transceiver is integral to the
Compass Mini-Trip Computer (CMTC), which is
located in the overhead console. The only visible com-
ponent of the universal transmitter are the three
transmitter push buttons (Fig. 7) centered between
the four CMTC push buttons located just rearward of
the CMTC display screen in the overhead console.
The three universal transmitter push buttons are
identified with one, two or three light indicators so
that they be easily identified by sight or by feel.
Each of the three universal transmitter push but-
tons controls an independent radio transmitter chan-
nel. Each of these three channels can be trained totransmit a different radio frequency signal for the
remote operation of garage door openers, motorized
gate openers, home or office lighting, security sys-
tems or just about any other device that can be
equipped with a radio receiver in the 286 to 399
MegaHertz (MHz) frequency range for remote opera-
tion. The universal transmitter is capable of operat-
ing systems using either rolling code or non-rolling
code technology.
The CMTC module displays messages and a small
house-shaped icon with one, two or three dots corre-
sponding to the three transmitter buttons to indicate
the status of the Universal Transmitter.
The Universal Transmitter cannot be repaired, and
is available for service only as a unit with the CMTC
module. This unit includes the push button switches
and the plastic module and display lens. If any of
these components is faulty or damaged, the complete
CMTC module must be replaced.
OPERATION
The universal transmitter operates on a non-
switched source of battery current so the unit will
remain functional, regardless of the ignition switch
position. For more information on the features, pro-
gramming procedures and operation of the universal
transmitter, see the owner's manual in the vehicle
glove box.
DIAGNOSIS AND TESTING - UNIVERSAL
TRANSMITTER
If the Universal Transmitter is inoperative, but the
Compass Mini-Trip Computer (CMTC) is operating
normally, see the owner's manual in the vehicle glove
box for instructions on training the universal trans-
mitter. Retrain the universal transmitter with a
known good transmitter as instructed in the owner's
manual and test the universal transmitter operation
again. If the unit is still inoperative, replace the
faulty universal transmitter and CMTC module as a
unit. If both the universal transmitter and the CMTC
module are inoperative, refer toDiagnosis and
Testing the Compass Mini-Trip Computerin this
section for further diagnosis. For complete circuit
diagrams, refer toOverhead Consolein Wiring
Diagrams.
STANDARD PROCEDURE
STANDARD PROCEDURE - ERASING
TRANSMITTER CODES
To erase the universal transmitter codes, simply
hold down buttons 1 and 3 until the two green dots
below the house symbol begin to flash.
Fig. 7 Overhead Console With Universal Transmitter
8M - 8 MESSAGE SYSTEMSKJ
COMPASS/MINI-TRIP COMPUTER (Continued)

NOTE: Individual channels cannot be erased. Eras-
ing the transmitter codes will erase ALL pro-
grammed codes.
STANDARD PROCEDURE - SETTING
TRANSMITTER CODES
(1) Turn off the engine.
(2) Erase the factory test codes by pressing but-
tons 1 and 3. Release the buttons when the two
green lights begin to flash (about 20 seconds).
(3) Choose one of the three buttons to train. Place
the hand-held transmitter within one inch of the uni-
versal transmitter and push the buttons on both
transmitters. The green dot below the house symbol
will begin to flash slowly.
(4) When the red light on the universal transmit-
ter begins to flash rapidly (this may take as long as
60 seconds), release both buttons. Your universal
transmitter is now ªtrainedº. To train the other but-
tons, repeat Step 3 and Step 4. Be sure to keep your
hand-held transmitter in case you need to retrain the
universal transmitter.
AMBIENT TEMP SENSOR
DESCRIPTION
Ambient air temperature is monitored by the Com-
pass Mini-Trip Computer (CMTC) through ambient
temperature sensor messages received from the Body
Control Module (BCM) over the Programmable Com-
munications Interface (PCI) data bus network. The
BCM receives a hard wired input from the ambient
temperature sensor. The ambient temperature sensor
(Fig. 8) is a variable resistor mounted in front the
radiator, behind the grille, near the center of the
vehicle.
Refer toBody Control Modulein Electronic Con-
trol Modules. For complete circuit diagrams, refer to
the appropriate wiring information. The ambient
temperature sensor cannot be adjusted or repaired
and, if faulty or damaged, it must be replaced.
OPERATION
The ambient temperature sensor is a variable
resistor that operates on a five-volt reference signal
sent to it by the BCM. The resistance in the sensor
changes as temperature changes, changing the tem-
perature sensor signal circuit voltage to the BCM.
Based upon the resistance in the sensor, the BCM
senses a specific voltage on the temperature sensor
signal circuit, which it is programmed to correspond
to a specific temperature. The BCM then sends the
proper ambient temperature messages to the CMTC
over the PCI data bus.
The thermometer function is supported by the
ambient temperature sensor, a wiring circuit, the
Body Control Module (BCM), the Programmable
Communications Interface (PCI) data bus, and a por-
tion of the Compass Mini-Trip Computer module.
The ambient temperature sensor circuit can also be
diagnosed by referring toDiagnosis and Testing -
Ambient Temperature Sensor, and Diagnosis
and Testing - Ambient Temperature Sensor Cir-
cuit. If the temperature sensor and circuit are con-
firmed to be OK, but the temperature display is
inoperative or incorrect, refer toDiagnosis and
Testing - Compass Mini-Trip Computerin this
section. For complete circuit diagrams, refer to the
appropriate wiring information.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector.
(2) Measure the resistance of the ambient temper-
ature sensor. At ±40É C (±40É F), the sensor resis-
tance is 336 kilohms. At 55É C (140É F), the sensor
resistance is 2.488 kilohms. The sensor resistance
should read between these two values. If OK, refer to
Diagnosis and Testing - Ambient Temperature
Sensor Circuitin this group. If not OK, replace the
faulty ambient temperature sensor.
DIAGNOSIS AND TESTING - AMBIENT
TEMPERATURE SENSOR CIRCUIT
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Disconnect the ambient temperature sensor wire har-
ness connector and the Body Control Module wire
harness connector.
(2) Connect a jumper wire between the two termi-
nals in the body half of the ambient temperature sen-
sor wire harness connector.
Fig. 8 Ambient Temperature Sensor
KJMESSAGE SYSTEMS 8M - 9
UNIVERSAL TRANSMITTER (Continued)

(3) Check for continuity between the sensor return
circuit and the ambient temperature sensor signal
circuit cavities of the BCM wire harness connector.
There should be continuity. If OK, go to Step 4. If not
OK, repair the open sensor return circuit or ambient
temperature sensor signal circuit to the ambient tem-
perature sensor as required.
(4) Remove the jumper wire from the body half of
the ambient temperature sensor wire harness con-
nector. Check for continuity between the sensor
return circuit cavity of the BCM wire harness con-
nector and a good ground. There should be no conti-
nuity. If OK, go to Step 5. If not OK, repair the
shorted sensor return circuit as required.
(5) Check for continuity between the ambient tem-
perature sensor signal circuit cavity of the BCM wire
harness connector and a good ground. There should
be no continuity. If OK, refer toDiagnosis and
Testing - Compass Mini-Trip Computerin this
group. If not OK, repair the shorted ambient temper-
ature sensor signal circuit as required.REMOVAL
(1) Open hood, disconnect and isolate the negative
battery cable.
(2) Remove the grille from the vehicle (Refer to 23
- BODY/EXTERIOR/GRILLE - REMOVAL).
(3) Disconnect the ambient temperature sensor
electrical connector.
(4) Remove the ambient temperature sensor
retaining screw and remove the sensor from the vehi-
cle.
INSTALLATION
(1) Position the ambient temperature sensor and
install the retaining screw.
(2) Connect the ambient temperature sensor elec-
trical connector.
(3) Install the grille on the vehicle (Refer to 23 -
BODY/EXTERIOR/GRILLE - INSTALLATION).
(4) Connect the negative battery cable.
8M - 10 MESSAGE SYSTEMSKJ
AMBIENT TEMP SENSOR (Continued)