2003 JEEP GRAND CHEROKEE Sw 10-12

An optional engine block heater (Fig. 13) is avail-
able with all models. The heater is equipped with a
power cord. The cord is attached to an engine com-
partment component with tie-straps. The heater
warms the engine providing easier engine starting
and faster warm-up in low temperatures. The heater
is mounted in a core hole of the engine cylinder block
in place of a freeze plug with the heating element
immersed in engine coolant.
OPERATION
Connecting the power cord to a grounded 110-120
volt AC electrical outlet with a grounded, three wire
extension cord activates the heating element warm-
ing the engine coolant.
DIAGNOSIS AND TESTINGÐENGINE BLOCK
HEATER
If the unit does not operate (Fig. 14) (Fig. 15), pos-
sible causes can be either the power cord or the
heater element. Test the power cord for continuity
with a 110-volt voltmeter or 110-volt test light. Test
heater element continuity with an ohmmeter or a
12-volt test light.
CAUTION: To prevent damage, the power cord must
be secured in it's retainer clips and away from any
components that may cause abrasion or damage,
such as linkages, exhaust components, etc.
REMOVAL
REMOVALÐ4.7L ENGINE
(1) Disconnect negative battery cable from battery.
(2) Drain coolant from radiator (Refer to 7 -
COOLING - STANDARD PROCEDURE).
Fig. 12 Engine Block HeaterÐ4.7L
1 - ENGINE BLOCK HEATER
Fig. 13 Block Heater
1 - ENGINE BLOCK HEATER
Fig. 14 Engine Block Heater 4.0L Engine
1 - ENGINE BLOCK HEATER
WJENGINE 7 - 33
ENGINE BLOCK HEATER (Continued)

8W-10 POWER DISTRIBUTION
Component Page
A/C Compressor Clutch................. 8W-10-32
A/C Compressor Clutch Relay . . . 8W-10-13, 14, 25, 26, 32
Accessory Delay Relay.................. 8W-10-24
Auto Shut Down Relay....... 8W-10-11, 14, 19, 20, 25
Battery.......................... 8W-10-11, 12
Blower Motor................... 8W-10-11, 12, 15
Blower Motor Controller............ 8W-10-11, 12, 15
Body Control Module................ 8W-10-27, 29
Camshaft Position Sensor................ 8W-10-26
Capacitor........................ 8W-10-19, 20
Capacitor No. 1....................... 8W-10-22
Capacitor No. 2....................... 8W-10-22
Cigar Lighter Relay.................... 8W-10-15
Circuit Breaker No. 1 (JB)............... 8W-10-29
Circuit Breaker No. 2 (JB)............... 8W-10-24
Coil On Plug No. 1.................... 8W-10-22
Coil On Plug No. 2.................... 8W-10-22
Coil On Plug No. 3.................... 8W-10-22
Coil On Plug No. 4.................... 8W-10-22
Coil On Plug No. 5.................... 8W-10-22
Coil On Plug No. 6.................... 8W-10-22
Coil On Plug No. 7.................... 8W-10-22
Coil On Plug No. 8.................... 8W-10-22
Coil Rail......................... 8W-10-19, 20
Controller Antilock
Brake............ 8W-10-11, 12, 13, 14, 17, 18, 32
Crankcase Heater..................... 8W-10-26
Driver Door Module.................... 8W-10-30
EGR Solenoid........................ 8W-10-26
Engine Control Module............ 8W-10-14, 26, 31
Engine Starter Motor................... 8W-10-27
Engine Starter Motor Relay.............. 8W-10-27
Fog Lamp Relay...................... 8W-10-24
Fuel Injector No. 1..................... 8W-10-21
Fuel Injector No. 2..................... 8W-10-21
Fuel Injector No. 3..................... 8W-10-21
Fuel Injector No. 4..................... 8W-10-21
Fuel Injector No. 5..................... 8W-10-21
Fuel Injector No. 6..................... 8W-10-21
Fuel Injector No. 7..................... 8W-10-21
Fuel Injector No. 8..................... 8W-10-21
Fuel Pressure Solenoid.................. 8W-10-26
Fuel Pump Module.................... 8W-10-32
Fuel Pump Relay................... 8W-10-13, 32
Fuse 1........................ 8W-10-11, 12, 15
Fuse 2........................ 8W-10-11, 12, 15
Fuse 3........................ 8W-10-11, 12, 16
Fuse 4..................... 8W-10-11, 12, 17, 18
Fuse 5........................ 8W-10-11, 17, 30
Fuse 6................ 8W-10-11, 12, 16, 18, 19, 20
Fuse 7..................... 8W-10-11, 12, 24, 30
Fuse 8..................... 8W-10-11, 12, 27, 30
Fuse 9............................. 8W-10-30
Fuse 10............................ 8W-10-30
Fuse 11....................... 8W-10-12, 15, 18
Fuse 12.................. 8W-10-11, 12, 14, 29, 30
Fuse 13....................... 8W-10-12, 14, 25
Fuse 14.................. 8W-10-11, 13, 14, 16, 27
Fuse 15.................. 8W-10-11, 13, 14, 16, 30
Fuse 16.................. 8W-10-16, 19, 20, 23, 25
Component Page
Fuse 17............................ 8W-10-16
Fuse 18.................... 8W-10-13, 14, 30, 31
Fuse 20............................ 8W-10-28
Fuse 21.................... 8W-10-13, 14, 29, 32
Fuse 22....................... 8W-10-14, 29, 31
Fuse 23....................... 8W-10-14, 24, 25
Fuse 24....................... 8W-10-13, 24, 32
Fuse 25.................... 8W-10-13, 14, 24, 32
Fuse 26.................... 8W-10-15, 19, 20, 25
Fuse 27.................... 8W-10-13, 14, 24, 31
Fuse 28.......................... 8W-10-17, 29
Fuse 29............................ 8W-10-29
Fuse 30............................ 8W-10-29
Fuse 31............................ 8W-10-28
Fuse 32............................ 8W-10-29
Fuse 33............................ 8W-10-28
Fusible Link...................... 8W-10-11, 12
G200.............................. 8W-10-27
Generator...................... 8W-10-11, 12, 26
Glow Plug No. 1...................... 8W-10-18
Glow Plug No. 2...................... 8W-10-18
Glow Plug No. 3...................... 8W-10-18
Glow Plug No. 4...................... 8W-10-18
Glow Plug No. 5...................... 8W-10-18
Glow Plug Relay No. 1............. 8W-10-12, 18, 26
Glow Plug Relay No. 2............. 8W-10-12, 18, 26
High Beam Relay..................... 8W-10-16
Horn No. 1.......................... 8W-10-31
Horn No. 2.......................... 8W-10-31
Horn Relay..................... 8W-10-13, 14, 31
Hydraulic Cooling Module........ 8W-10-19, 20, 23, 26
Ignition Switch............. 8W-10-11, 14, 27, 28, 29
Intake Port Swirl Actuator............... 8W-10-26
Junction Block............. 8W-10-11, 12, 13, 14, 15,
16, 24, 28, 29, 30
Low Beam Relay...................... 8W-10-16
Low Beam/Daytime Running Lamp Relay.... 8W-10-16
Mass Air Flow Sensor.................. 8W-10-26
Oxygen Sensor 1/1 Upstream........... 8W-10-19, 20
Oxygen Sensor 1/2 Downstream......... 8W-10-19, 20
Oxygen Sensor 1/2 Downstream........... 8W-10-23
Oxygen Sensor 2/2 Downstream........... 8W-10-23
Oxygen Sensor Downstream Relay.... 8W-10-19, 20, 23
Park Lamp Relay..................... 8W-10-16
Passenger Door Module................. 8W-10-30
Power Distribution Center...... 8W-10-2, 3, 11, 12, 13,
14, 15, 16, 17, 18, 19, 20,
24, 25, 27, 30, 31, 32
Powertrain Control Module......... 8W-10-13, 19, 20
Rear Power Outlet............. 8W-10-13, 14, 24, 31
Rear Window Defogger.................. 8W-10-15
Rear Window Defogger Relay............. 8W-10-15
Trailer Tow Circuit Breaker.............. 8W-10-15
Transmission Control Module........... 8W-10-11, 17
Transmission Control Relay............ 8W-10-11, 17
Transmission Solenoid.................. 8W-10-17
Transmission Solenoid/TRS Assembly....... 8W-10-17
Viscous/Cabin Heater Relay......... 8W-10-14, 25, 26
Wastegate Solenoid.................... 8W-10-26
Water In Fuel Sensor................... 8W-10-26
WJ8W-10 POWER DISTRIBUTION 8W - 10 - 1