Jeep cherokee 2000 Service Manual page 853

XJ
DESCRIPTION AND OPERATION
POWERTRAIN CONTROL MODULE (PCM) . . . . . 25
MODES OF OPERATION . . . . . . . . . . . . . . . . . . . 26
AUTOMATIC SHUTDOWN (ASD) RELAY
SENSE-PCM INPUT . . . . . . . . . . . . . . . . . . . . 29
BATTERY VOLTAGE-PCM INPUT. . . . . . . . . . . . 29
BRAKE SWITCH-PCM INPUT. . . . . . . . . . . . . . . 29
FIVE VOLT SENSOR SUPPLIES-PRIMARY
AND SECONDARY . . . . . . . . . . . . . . . . . . . . . . 29
FUEL LEVEL SENSOR-PCM INPUT . . . . . . . . . . 30
ENGINE COOLANT TEMPERATURE
SENSOR-PCM INPUT . . . . . . . . . . . . . . . . . . . 30
EXTENDED IDLE SWITCH-PCM INPUT . . . . . . . 30
OXYGEN SENSOR-PCM INPUT. . . . . . . . . . . . . 30
IGNITION CIRCUIT SENSE-PCM INPUT . . . . . . 31
INTAKE MANIFOLD AIR TEMPERATURE
SENSOR-PCM INPUT . . . . . . . . . . . . . . . . . . . 32
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSOR-PCM INPUT . . . . . . . . . . . . . . . . . . . 32
OIL PRESSURE SENSOR-PCM INPUT . . . . . . . 33
POWER GROUNDS . . . . . . . . . . . . . . . . . . . . . . . 33
POWER STEERING PRESSURE SWITCH-
PCM INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
SENSOR RETURN-PCM INPUT . . . . . . . . . . . . . 34
THROTTLE POSITION SENSOR (TPS)-PCM
INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
VEHICLE SPEED AND DISTANCE SENSOR-
PCM INPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
AUTO SHUTDOWN (ASD) RELAY-PCM
OUTPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
CCD BUS (+/-) CIRCUITS-PCM OUTPUTS . . . . . . 35
DATA LINK CONNECTOR-PCM INPUT AND
OUTPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
DESCRIPTION AND OPERATION
POWERTRAIN CONTROL MODULE (PCM)
DESCRIPTION
The Powertrain Control Module (PCM) is located
in the engine compartment (Fig. 1). The PCM is
referred to as JTEC.
OPERATION
The PCM operates the fuel system. The PCM is a
pre-programmed, triple microprocessor digital com-
puter. It regulates ignition timing, air-fuel ratio,
emission control devices, charging system, certain
FUEL INJECTION SYSTEM
TABLE OF CONTENTS
page
FUEL INJECTORS-PCM OUTPUT . . . . . . . . . . . 35
FUEL PUMP RELAY-PCM OUTPUT . . . . . . . . . . . 35
IDLE AIR CONTROL (IAC) MOTOR-PCM
OUTPUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
RADIATOR FAN RELAY-PCM OUTPUT . . . . . . . 36
THROTTLE BODY . . . . . . . . . . . . . . . . . . . . . . . . 36
DIAGNOSIS AND TESTING
VISUAL INSPECTION. . . . . . . . . . . . . . . . . . . . . . 37
ASD AND FUEL PUMP RELAYS . . . . . . . . . . . . . . 41
THROTTLE BODY MINIMUM AIR FLOW
CHECK PROCEDURE . . . . . . . . . . . . . . . . . . . . 42
REMOVAL AND INSTALLATION
AUTOMATIC SHUTDOWN (ASD) RELAY . . . . . . . 43
FUEL PUMP RELAY . . . . . . . . . . . . . . . . . . . . . . . 44
THROTTLE BODY . . . . . . . . . . . . . . . . . . . . . . . . 44
THROTTLE POSITION SENSOR (TPS) . . . . . . . . 45
IDLE AIR CONTROL (IAC) MOTOR . . . . . . . . . . . 45
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
POWERTRAIN CONTROL MODULE (PCM) . . . . . 46
POWER STEERING PRESSURE SWITCH-
2.5L ENGINE. . . . . . . . . . . . . . . . . . . . . . . . . . . 47
OXYGEN SENSOR. . . . . . . . . . . . . . . . . . . . . . . . 47
AIR CLEANER ELEMENT (FILTER) . . . . . . . . . . . 49
ENGINE COOLANT TEMPERATURE SENSOR. . . 49
INTAKE MANIFOLD AIR TEMPERATURE
SENSOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
VEHICLE SPEED SENSOR . . . . . . . . . . . . . . . . . 51
SPECIFICATIONS
TORQUE CHART . . . . . . . . . . . . . . . . . . . . . . . . . 51
SPECIAL TOOLS
FUEL SYSTEM. . . . . . . . . . . . . . . . . . . . . . . . . . . 52
transmission features, speed control, air conditioning
compressor clutch engagement and idle speed. The
PCM can adapt its programming to meet changing
operating conditions.
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as Powertrain Control Module
(PCM) Outputs. The sensors and switches that pro-
vide inputs to the PCM are considered Powertrain
Control Module (PCM) Inputs.
The PCM adjusts ignition timing based upon
inputs it receives from sensors that react to: engine
rpm, manifold absolute pressure, engine coolant tem-
FUEL SYSTEM 14 - 25
page