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DR
POWERTRAIN CONTROL MODULE (Continued)
OPERATION
OPERATION - PCM
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
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-
perature, throttle position, transmission gear selec-
tion (automatic transmission), vehicle speed, power
steering pump pressure, and the brake switch.
The PCM adjusts idle speed based on inputs it
receives from sensors that react to: throttle position,
vehicle speed, transmission gear selection, engine
coolant temperature and from inputs it receives from
the air conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
NOTE: PCM Inputs:
• ABS module (if equipped)
• A/C request (if equipped with factory A/C)
• A/C select (if equipped with factory A/C)
• A/C pressure transducer
• Auto shutdown (ASD) sense
• Battery temperature sensor
• Battery voltage
• Brake switch
• J1850 bus (+) circuits
• J1850 bus (-) circuits
• Camshaft position sensor signal
• Crankshaft position sensor
• Data link connection for DRB scan tool
• EATX module (if equipped)
• Engine coolant temperature sensor
• Fuel level (through J1850 circuitry)
• Generator (battery voltage) output
• Ignition circuit sense (ignition switch in on/off/
crank/run position)
ELECTRONIC CONTROL MODULES
• Intake manifold air temperature sensor
• Knock sensors (2 on 3.7L engine)
• Leak detection pump (switch) sense (if equipped)
• Manifold absolute pressure (MAP) sensor
• Oil pressure
• Oxygen sensors
• Park/neutral switch (auto. trans. only)
• Power ground
• Power steering pressure switch (if equipped)
• Sensor return
• Signal ground
• Speed control multiplexed single wire input
• Throttle position sensor
• Transfer case switch (4WD range position)
• Vehicle speed signal
NOTE: PCM Outputs:
• A/C clutch relay
• Auto shutdown (ASD) relay
• J1850 bus (+/-) circuits for: speedometer, voltme-
ter, fuel gauge, oil pressure gauge/lamp, engine temp.
gauge and speed control warn. lamp
• Data link connection for DRB scan tool
• EGR valve control solenoid (if equipped)
• EVAP canister purge solenoid
• Five volt sensor supply (primary)
• Five volt sensor supply (secondary)
• Fuel injectors
• Fuel pump relay
• Generator field driver (-)
• Generator field driver (+)
• Idle air control (IAC) motor
• Ignition coil(s)
• Leak detection pump (if equipped)
• Malfunction indicator lamp (Check engine lamp).
Driven through J1850 circuits.
• Oxygen sensor heater relays
• Oxygen sensors (pulse width modulated)
• Radiator cooling fan relay (pulse width modu-
lated)
• Speed control vacuum solenoid
• Speed control vent solenoid
• Tachometer (if equipped). Driven through J1850
circuits.
• Transmission convertor clutch circuit. Driven
through J1850 circuits.
OPERATION - 5 VOLT SUPPLIES
Primary 5–volt supply:
• supplies the required 5 volt power source to the
Crankshaft Position (CKP) sensor.
• supplies the required 5 volt power source to the
Camshaft Position (CMP) sensor.
• supplies a reference voltage for the Manifold
Absolute Pressure (MAP) sensor.
8E - 11
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