2003 JEEP GRAND CHEROKEE Battery cable

(b) If the voltage reads above 9.6 volts and the
current (amperage) draw reads below specifica-
tions, refer toFeed Circuit Testin this section.
(c) If the voltage reads 12.5 volts or greater and
the starter motor does not turn, refer toControl
Circuit Testingin this section.
(d) If the voltage reads 12.5 volts or greater and
the starter motor turns very slowly, refer toFeed
Circuit Testin this section.
NOTE: A cold engine will increase the starter cur-
rent (amperage) draw reading, and reduce the bat-
tery voltage reading.
FEED CIRCUIT TEST
The starter feed circuit test (voltage drop method)
will determine if there is excessive resistance in the
high-amperage feed circuit. For complete circuit dia-
grams, refer toStarting Systemin the Contents of
Group 8W - Wiring Diagrams.
When performing these tests, it is important to
remember that the voltage drop is giving an indica-
tion of the resistance between the two points at
which the voltmeter probes are attached.
Example:When testing the resistance of the bat-
tery positive cable, touch the voltmeter leads to the
battery positive cable clamp and the cable connector
at the starter solenoid. If you probe the battery pos-
itive terminal post and the cable connector at the
starter solenoid, you are reading the combined volt-
age drop in the battery positive cable clamp-to-termi-
nal post connection and the battery positive cable.
The following operation will require a voltmeter
accurate to 1/10 (0.10) volt. Before performing the
tests, be certain that the following procedures are
accomplished:
²Battery is fully-charged and load-tested. Refer to
Batteryin the Diagnosis and Testing section of
Group 8A - Battery for the procedures.
²Fully engage the parking brake.
²Place the automatic transmission gearshift selec-
tor lever in the Park position.
²
Verify that all lamps and accessories are turned off.
²To prevent the engine from starting, remove the
Automatic ShutDown (ASD) relay. The ASD relay is
located in the Power Distribution Center (PDC), in
the engine compartment. Refer to the fuse and relay
layout label affixed to the underside of the PDC cover
for ASD relay identification and location.
(1) Connect the positive lead of the voltmeter to
the battery negative terminal post. Connect the neg-
ative lead of the voltmeter to the battery negative
cable clamp (Fig. 2). Rotate and hold the ignition
switch in the Start position. Observe the voltmeter. If
voltage is detected, correct the poor contact between
the cable clamp and the terminal post.(2) Connect the positive lead of the voltmeter to
the battery positive terminal post. Connect the nega-
tive lead of the voltmeter to the battery positive cable
clamp (Fig. 3). Rotate and hold the ignition switch in
the Start position. Observe the voltmeter. If voltage
is detected, correct the poor contact between the
cable clamp and the terminal post.
(3) Connect the voltmeter to measure between the
battery positive terminal post and the starter sole-
noid battery terminal stud (Fig. 4). Rotate and hold
the ignition switch in the Start position. Observe the
voltmeter. If the reading is above 0.2 volt, clean and
tighten the battery cable connection at the solenoid.
Fig. 2 Test Battery Negative Connection Resistance
- Typical
1 - VOLTMETER
2 - BATTERY
Fig. 3 Test Battery Positive Connection Resistance -
Typical
1 - VOLTMETER
2 - BATTERY
WJSTARTING 8F - 33
STARTING (Continued)

Repeat the test. If the reading is still above 0.2 volt,
replace the faulty battery positive cable.
(4) Connect the voltmeter to measure between the
battery negative terminal post and a good clean
ground on the engine block (Fig. 5). Rotate and hold
the ignition switch in the Start position. Observe the
voltmeter. If the reading is above 0.2 volt, clean and
tighten the battery negative cable attachment on the
engine block. Repeat the test. If the reading is still
above 0.2 volt, replace the faulty battery negative
cable.(5) Connect the positive lead of the voltmeter to
the starter housing. Connect the negative lead of the
voltmeter to the battery negative terminal post (Fig.
6). Rotate and hold the ignition switch in the Start
position. Observe the voltmeter. If the reading is
above 0.2 volt, correct the poor starter to engine
block ground contact.
If the resistance tests detect no feed circuit prob-
lems, refer toStarter Motorin the Diagnosis and
Testing section of this group.
CONTROL CIRCUIT TESTING
The starter control circuit components should be
tested in the order in which they are listed, as fol-
lows:
²Starter Relay- Refer toStarter Relayin the
Diagnosis and Testing section of this group for the
procedures.
²Starter Solenoid- Refer toStarter Motorin
the Diagnosis and Testing section of this group for
the procedures.
²Ignition Switch- Refer toIgnition Switch
and Key Lock Cylinderin the Diagnosis and Test-
ing section of Group 8D - Ignition System for the pro-
cedures.
²Park/Neutral Position Switch- Refer to
Park/Neutral Position Switchin the Diagnosis
and Testing section of Group 21 - Transmission for
the procedures.
²Wire harnesses and connections- Refer to
Starting Systemin the Contents of Group 8W -
Wiring Diagrams for complete circuit diagrams.
Fig. 4 Test Battery Positive Cable Resistance -
Typical
1 - BATTERY
2 - VOLTMETER
3 - STARTER MOTOR
Fig. 5 Test Ground Circuit
1 - VOLTMETER
2 - BATTERY
3 - ENGINE GROUND
Fig. 6 Test Starter Ground - Typical
1 - STARTER MOTOR
2 - BATTERY
3 - VOLTMETER
8F - 34 STARTINGWJ
STARTING (Continued)

REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Raise and support the vehicle.
(3) Remove the lower (forward facing) mounting
screw securing the starter motor to the automatic
transmission torque converter housing (Fig. 9) or
(Fig. 10) .
(4) While supporting the starter motor with one
hand, use the other hand to remove the upper (rear
facing) mounting screw securing the starter motor to
the automatic transmission torque converter housing.
(5) Lower the starter motor from the front of the
automatic transmission torque converter housing far
enough to access and remove the nut that secures
the battery cable eyelet to the solenoid battery termi-
nal (Fig. 11) or (Fig. 12) . Always support the starter
motor during this process, do not let the starter
motor hang from the wire harness.
(6) Remove the battery cable eyelet from the sole-
noid battery terminal. Always support the starter
motor during this process, do not let the starter
motor hang from the wire harness.
(7) Disconnect the solenoid terminal wire harness
connector from the connector receptacle on the
starter solenoid. Always support the starter motor
during this process, do not let the starter motor hang
from the wire harness.
Fig. 9 Starter Motor Remove/Install - 4.0L Engine
1 - SCREW
2 - STARTER MOTOR
3 - SCREW
Fig. 10 Starter Motor Remove/Install - 4.7L Engine
1 - SCREW
2 - STARTER MOTOR
3 - SCREW
Fig. 11 Starter Wire Harness Remove/Install - 4.0L
Engine
1 - BATTERY, STARTER AND GENERATOR WIRE HARNESS
2 - GROUND EYELET
3 - SCREW
4 - NUT
5 - SOLENOID TERMINAL CONNECTOR
6 - SOLENOID BATTERY TERMINAL EYELET
7 - RETAINERS
WJSTARTING 8F - 37
STARTER MOTOR (Continued)

(8) Remove the starter motor from the engine com-
partment.
INSTALLATION
(1) Position the starter motor in the engine com-
partment.
(2) Reconnect the solenoid terminal wire harness
connector to the connector receptacle on the starter
solenoid. Always support the starter motor during
this process, do not let the starter motor hang from
the wire harness.
(3) Install the battery cable eyelet onto the sole-
noid battery terminal. Always support the starter
motor during this process, do not let the starter
motor hang from the wire harness.
(4) Install and tighten the nut that secures the
battery cable eyelet to the solenoid battery terminal.
Tighten the nut to 11.3 N´m (100 in. lbs.). Always
support the starter motor during this process, do not
let the starter motor hang from the wire harness.
(5) Position the starter motor to the front of the
automatic transmission torque converter housing and
loosely install both the upper and lower mounting
screws.
(6) Tighten the lower (forward facing) starter
motor mounting screw. On 4.0L engines, tighten the
screw to 41 N´m (30 ft. lbs.). On 4.7L engines, tighten
the screw to 54 N´m (40 ft. lbs.).(7) Tighten the upper (rearward facing) starter
mounting screw. Tighten the screw to 54 N´m (40 ft.
lbs.).
(8) Lower the vehicle.
(9) Reconnect the battery negative cable.
STARTER MOTOR RELAY
DESCRIPTION
The starter relay is an electromechanical device
that switches battery current to the pull-in coil of the
starter solenoid when the ignition switch is turned to
the Start position. The starter relay is located in the
Power Distribution Center (PDC), in the engine com-
partment. See the fuse and relay layout label affixed
to the inside surface of the PDC cover for starter
relay identification and location.
The starter relay is a International Standards
Organization (ISO) micro-relay. Relays conforming to
the ISO specifications have common physical dimen-
sions, current capacities, terminal patterns, and ter-
minal functions. The ISO micro-relay terminal
functions are the same as a conventional ISO relay.
However, the ISO micro-relay terminal pattern (or
footprint) is different, the current capacity is lower,
and the physical dimensions are smaller than those
of the conventional ISO relay.
The starter relay cannot be repaired or adjusted
and, if faulty or damaged, it must be replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact.
When the electromagnetic coil is de-energized,
spring pressure returns the movable contact to the
normally closed position. The resistor or diode is con-
nected in parallel with the electromagnetic coil in the
relay, and helps to dissipate voltage spikes that are
produced when the coil is de-energized.
DIAGNOSIS AND TESTING - STARTER RELAY
The starter relay (Fig. 13) is located in the Power
Distribution Center (PDC), in the engine compart-
ment. Refer to the fuse and relay layout label affixed
to the underside of the PDC cover for starter relay
identification and location. For complete circuit dia-
grams, refer toStarting Systemin the Contents of
Group 8W - Wiring Diagrams.
Fig. 12 Starter Wire Harness Remove/Install - 4.7L
Engine
1 - SOLENOID BATTERY TERMINAL EYELET
2 - NUT
3 - SOLENOID TERMINAL CONNECTOR
4 - BATTERY STARTER AND GENERATOR WIRE HARNESS
5 - RETAINERS
8F - 38 STARTINGWJ
STARTER MOTOR (Continued)

(1) Remove the starter relay from the PDC. Refer
toStarter Relayin the Removal and Installation
section of this group for the procedures.
(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   5 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, perform the Relay Circuit Test that
follows. If not OK, replace the faulty relay.
RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair the open
circuit to the fuse in the PDC as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
(3) The relay normally open terminal (87) is con-
nected to the common feed terminal (30) in the ener-
gized position. This terminal supplies battery voltage
to the starter solenoid field coils. There should be
continuity between the cavity for relay terminal 87
and the starter solenoid terminal at all times. If OK,
go to Step 4. If not OK, repair the open circuit to the
starter solenoid as required.
(4) The coil battery terminal (86) is connected to
the electromagnet in the relay. It is energized when
the ignition switch is held in the Start position.
Check for battery voltage at the cavity for relay ter-
minal 86 with the ignition switch in the Start posi-tion, and no voltage when the ignition switch is
released to the On position. If OK, go to Step 5. If
not OK, check for an open or short circuit to the igni-
tion switch and repair, if required. If the circuit to
the ignition switch is OK, refer toIgnition Switch
and Key Lock Cylinderin the Diagnosis and Test-
ing section of Group 8D - Ignition System for testing
of the ignition switch.
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. It is grounded
through the park/neutral position switch only when
the gearshift selector lever is in the Park or Neutral
positions. Check for continuity to ground at the cav-
ity for relay terminal 85. If not OK, check for an
open or short circuit to the park/neutral position
switch and repair, if required. If the circuit to the
park/neutral position switch is OK, refer toPark/
Neutral Position Switchin the Diagnosis and
Testing section of Group 21 - Transmission for testing
of the park/neutral position switch.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the cover from the Power Distribution
Center (PDC) (Fig. 14) .
Fig. 13 Starter Relay
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
Fig. 14 Power Distribution Center
1 - RIGHT FENDER
2 - BATTERY
3 - POWER DISTRIBUTION CENTER
4 - COVER
WJSTARTING 8F - 39
STARTER MOTOR RELAY (Continued)

(3) See the fuse and relay layout label affixed to
the underside of the PDC cover for starter relay iden-
tification and location.
(4) Remove the starter relay from the PDC.
INSTALLATION
(1) See the fuse and relay layout label affixed to
the underside of the PDC cover for the proper starter
relay location.
(2) Position the starter relay in the proper recep-
tacle in the PDC.(3) Align the starter relay terminals with the ter-
minal cavities in the PDC receptacle.
(4) Push down firmly on the starter relay until the
terminals are fully seated in the terminal cavities in
the PDC receptacle.
(5) Install the cover onto the PDC.
(6) Reconnect the battery negative cable.
8F - 40 STARTINGWJ
STARTER MOTOR RELAY (Continued)

²Passenger Door Module (PDM)- Refer to
Electronic Control Modules for more information.
OPERATION - REAR WINDOW DEFOGGER
The rear window defogger system is controlled by a
momentary switch that is integral to the a/c heater
control located in the center stack area of the instru-
ment panel. A Light-Emitting Diode (LED) in the
switch button will light to indicate when the rear
window defogger system is turned on. The BCM,
which contains the rear window defogger system
timer and control logic, monitors the status of the
defogger switch through a hard-wired input. The
BCM then sends control outputs through a hard
wired circuit to energize or de-energize the defogger
relay.
The electrically heated outside rear view mirror
heating grids are also controlled by the rear window
defogger switch. When the BCM receives an input
from the switch, it sends a defogger switch status
message to the DDM and the PDM over the PCI data
bus. The DDM and PDM respond to the defogger
switch status messages by energizing or de-energiz-
ing the battery current feed to their respective out-
side rear view mirror heating grids.
The rear window defogger system will be automat-
ically turned off after a programmed time interval of
about ten minutes. After the initial time interval has
expired, if the defogger switch is turned on again
during the same ignition cycle, the defogger system
will automatically turn off after about five minutes.
The defogger system will automatically shut off if the
ignition switch is turned to the Off position, or it can
be turned off manually by depressing the rear win-
dow defogger switch again.
See the owner's manual in the vehicle glove box for
more information on the features, use and operation
of the rear window defogger system.
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER SYSTEM
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.For complete circuit diagrams, (Refer to Appropri-
ate Wiring Information). The operation of the electri-
cally heated rear window defogger system can be
confirmed in one of the following manners:
1. Turn the ignition switch to the On position.
While monitoring the instrument panel voltmeter,
depress the rear window defogger switch to the On
position. When the rear window defogger switch is
turned On, a distinct voltmeter needle deflection
should be noted.
2. Turn the ignition switch to the On position.
Depress the rear window defogger switch to the On
position. The rear window defogger operation can be
checked by feeling the rear window or outside rear
view mirror glass. A distinct difference in tempera-
ture between the grid lines and the adjacent clear
glass or the mirror glass can be detected within three
to four minutes of operation.
3. Using a 12-volt DC voltmeter, contact the rear
glass heating grid terminal A (right side) with the
negative lead, and terminal B (left side) with the pos-
itive lead (Fig. 1). The voltmeter should read battery
voltage.
The above checks will confirm rear window defog-
ger system operation. Illumination of the rear win-
dow defogger switch LED indicator means that there
is battery current available at the output of the rear
window defogger relay, but does not confirm that bat-
tery current is reaching the rear glass heating grid
lines.
If the rear window defogger system does not oper-
ate, the problem should be isolated in the following
manner:
Fig. 1 REAR WINDOW GLASS GRID TEST
1 - TERMINAL ªAº
2 - TERMINAL ªBº
3 - FEED WIRE
4 - MID-POINT ªCº (TYPICAL)
5 - HEATED REAR WINDOW DEFOGGER GRID
6 - GROUND WIRE
8G - 2 HEATED GLASSWJ
HEATED GLASS (Continued)

not attach the wire harness connectors until the cur-
ing process is complete.
(11) Check the operation of the rear glass heating
grid.
REAR WINDOW DEFOGGER
RELAY
DESCRIPTION
The rear window defogger relay is an electrome-
chanical device that switches fused battery current to
the rear glass heating grid and the Light-Emitting
Diode (LED) indicator of the rear window defogger
switch, when the Body Control Module (BCM) rear
window defogger timer and logic circuitry grounds
the relay coil. The rear window defogger relay is
located in the junction block, under the left end of
the instrument panel in the passenger compartment.
The rear window defogger relay is a International
Standards Organization (ISO) relay. Relays conform-
ing to the ISO specifications have common physical
dimensions, current capacities, terminal patterns,
and terminal functions.
The rear window defogger relay cannot be repaired
or adjusted and, if faulty or damaged, it must be
replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one mov-
able) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the elec-
tromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact.
When the electromagnetic coil is de-energized,
spring pressure returns the movable contact to the
normally closed position. The resistor or diode is con-
nected in parallel with the electromagnetic coil in the
relay, and helps to dissipate voltage spikes that are
produced when the coil is de-energized.
DIAGNOSIS AND TESTING - REAR WINDOW
DEFOGGER RELAY
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
RELAY TEST
The rear window defogger relay (Fig. 4) is located
in the junction block, under the left end of the instru-
ment panel in the passenger compartment. Remove
the rear window defogger relay from the junction
block to perform the following tests:
(1) 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 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75   10 ohms. If OK, go to Step
3. If not OK, replace the faulty relay.
(3) 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, refer to theRelay Circuit Test.If
not OK, replace the faulty relay.
RELAY CIRCUIT TEST
(1) The relay common feed terminal cavity (30) is
connected to battery voltage and should be hot at all
times. If OK, go to Step 2. If not OK, repair the open
fused B(+) circuit to the Power Distribution Center
(PDC) fuse as required.
(2) The relay normally closed terminal (87A) is
connected to terminal 30 in the de-energized position,
but is not used for this application. Go to Step 3.
Fig. 4 REAR WINDOW DEFOGGER RELAY
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
WJHEATED GLASS 8G - 5
REAR WINDOW DEFOGGER GRID (Continued)