Jeep 1997 Grand Cherokee Service Manual page 745

ZG
DESCRIPTION AND OPERATION
ACCELERATOR PEDAL POSITION SENSOR
(DIESEL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
AUTOMATIC SHUT DOWN (ASD) RELAY . . . . . 34
AUTOMATIC SHUT DOWN RELAY (DIESEL) . . . 34
BATTERY FEED (DIESEL) . . . . . . . . . . . . . . . . . 33
BATTERY FEED . . . . . . . . . . . . . . . . . . . . . . . . 33
BATTERY TEMPERATURE SENSOR . . . . . . . . . 35
CAMSHAFT POSITION SENSOR . . . . . . . . . . . 36
CCD BUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
CRANKSHAFT POSITION SENSOR (DIESEL) . . 36
CRANKSHAFT POSITION SENSOR . . . . . . . . . 35
DATA LINK CONNECTOR . . . . . . . . . . . . . . . . . 34
DUTY CYCLE EVAP\PURGE SOLENOID . . . . . . 39
EGR SOLENOID (DIESEL) . . . . . . . . . . . . . . . . 39
ENGINE COOLANT TEMPERATURE SENSOR
(DIESEL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
ENGINE COOLANT TEMPERATURE SENSOR . 36
EVAPORATIVE SYSTEM LEAK DETECTION
PUMP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
FUEL HEATER (DIESEL) . . . . . . . . . . . . . . . . . . 39
FUEL INJECTION PUMP (DIESEL) . . . . . . . . . . 38
FUEL INJECTORS . . . . . . . . . . . . . . . . . . . . . . . 38
DESCRIPTION AND OPERATION
IGNITION SWITCH
Circuit A1 from fuse 8 in the Power Distribution
Center (PDC) powers four different circuits through
the ignition switch. When the ignition switch is in
the START or RUN position, it connects circuit A1 to
circuit A21.
In the ACCESSORY or RUN position, the ignition
switch connects to circuit A31. In the START posi-
tion, the ignition switch connects circuit A1 to circuit
A41. When the ignition switch is in the RUN position
it connects circuit A1 to circuit A22.
Also in the START position, the case grounded
ignition switch grounds circuit G9 from the brake
warning switch.
BATTERY FEED
Circuit F5 from fuse 20 in the Power Distribution
Center (PDC) supplies battery voltage to cavity A22
of the Powertrain Control Module (PCM).
HELPFUL INFORMATION
Circuit F5 also supplies power to the contact sides
of the Automatic Shut Down (ASD) relay.
8W - 30 FUEL/IGNITION SYSTEMS
8W-30 FUEL/IGNITION SYSTEMS
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INDEX
FUEL PUMP MODULE (DIESEL) . . . . . . . . . . . . 34
FUEL PUMP MODULE . . . . . . . . . . . . . . . . . . . . 34
FUEL PUMP RELAY . . . . . . . . . . . . . . . . . . . . . 34
GLOW PLUGS (DIESEL) . . . . . . . . . . . . . . . . . . 39
GROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
HEATED OXYGEN SENSORS . . . . . . . . . . . . . . 35
IDLE AIR CONTROL (IAC) MOTOR . . . . . . . . . . 39
IGNITION COIL . . . . . . . . . . . . . . . . . . . . . . . . . 39
IGNITION SWITCH . . . . . . . . . . . . . . . . . . . . . . 33
INSTRUMENTED FIRST INJECTOR (DIESEL) . . 39
INTAKE AIR TEMPERATURE SENSOR . . . . . . . 37
LOW COOLANT LEVEL SWITCH (DIESEL) . . . . 39
LOW IDLE POSITION SWITCH (DIESEL) . . . . . 37
MANIFOLD ABSOLUTE PRESSURE SENSOR . 37
MASS AIR FLOW SENSOR (DIESEL) . . . . . . . . 37
OIL PRESSURE SENSOR (DIESEL) . . . . . . . . . 38
OIL PRESSURE SENSOR . . . . . . . . . . . . . . . . . 38
PCM GROUND (DIESEL) . . . . . . . . . . . . . . . . . 34
THROTTLE POSITION SENSOR . . . . . . . . . . . . 36
VEHICLE SPEED SENSOR (DIESEL) . . . . . . . . 35
VEHICLE SPEED SENSOR . . . . . . . . . . . . . . . . 35
WATER IN FUEL SENSOR (DIESEL) . . . . . . . . . 38
BATTERY FEED (DIESEL)
Battery feed for the Powertrain Control Module
(PCM) is supplied from several sources. One is a con-
stant battery feed on circuit F6. This circuit is pro-
tected by a 15 amp fuse located in the Power
Distribution Center (PDC)
Battery voltage is also provided on circuit F99.
This circuit is HOT in the START and RUN position
and protected by a 15 amp fuse located in the PDC.
Power for the fuse is supplied on circuit A21 from the
ignition switch.
GROUND
Circuit Z12 connects to cavities A31 and A32 of the
PCM. The Z12 circuit provides ground for PCM inter-
nal drivers that operate high current devices like the
injectors and ignition coil.
Internal to the PCM, the ground circuit connects to
the PCM sensor return circuit (from circuit K4).
HELPFUL INFORMATION
• If the system loses ground for the Z12 circuits,
the vehicle will not operate. Check the connection at
the ganged-ground circuit eyelet.
8W - 30 - 33
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