Chrysler Stratus RHD 1999 Electronic Service Manual page 960

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DESCRIPTION AND OPERATION (Continued)
Based on inputs it receives, the PCM adjusts fuel
injector pulse width, idle speed, ignition spark
advance, ignition coil dwell and EVAP canister purge
operation. The PCM regulates the cooling fan, air
conditioning and speed control systems. The PCM
changes generator charge rate by adjusting the gen-
erator field. The PCM also performs diagnostics.
The PCM adjusts injector pulse width (air-fuel
ratio) based on the following inputs.
• Battery voltage
• Coolant temperature
• Exhaust gas content (oxygen sensor)
• Engine speed (crankshaft position sensor)
• Intake air temperature
• Manifold absolute pressure
• Throttle position
The PCM adjusts ignition timing based on the fol-
lowing inputs.
• Coolant temperature
• Engine speed (crankshaft position sensor)
• Knock sensor
• Manifold absolute pressure
• Throttle position
• Transmission
gear
switch)
• Intake air temperature
The PCM also adjusts engine idle speed through
the idle air control motor based on the following
inputs.
• Air conditioning sense
• Battery voltage
• Battery temperature
• Brake switch
• Coolant temperature
• Engine speed (crankshaft position sensor)
• Engine run time
• Manifold absolute pressure
• Power steering pressure switch
• Throttle position
• Transmission
gear
switch)
• Vehicle distance (speed)
The Auto Shutdown (ASD) and fuel pump relays
are located in the Power Distribution Center (PDC).
The camshaft position sensor (distributor pick-up
signal 2.5L) and crankshaft position sensor signals
are sent to the PCM. If the PCM does not receive the
signal within approximately 1 second of engine
cranking, it deactivates the ASD relay and fuel pump
relay. When these relays are deactivated, power is
shut off from the fuel injectors, ignition coils, oxygen
sensor heating elements and fuel pump.
The PCM contains a voltage converter that
changes battery voltage to a regulated 9 volts direct
selection (park/neutral
selection (park/neutral
current to power the camshaft position sensor, crank-
shaft position sensor and vehicle speed sensor. The
PCM also provides a 5 volt direct current supply for
the manifold absolute pressure sensor, throttle posi-
tion sensor, and A/C pressure switch.
AIR CONDITIONING PRESSURE
TRANSDUCER—PCM INPUT
OPERATION
The Powertrain Control Module (PCM) monitors
the A/C compressor discharge (high side) pressure
through the air conditioning pressure transducer.
The transducer supplies an input to the PCM. The
PCM engages the A/C compressor clutch if pressure
is sufficient for A/C system operation.
AUTOMATIC SHUTDOWN (ASD) SENSE—PCM
INPUT
OPERATION
The ASD sense circuit informs the PCM when the
ASD relay energizes. A 12 volt signal at this input
indicates to the PCM that the ASD has been acti-
vated. This input is used only to sense that the ASD
relay is energized.
When energized, the ASD relay supplies battery
voltage to the fuel injectors, ignition coils and the
heating element in each oxygen sensor. If the PCM
does not receive 12 volts from this input after
grounding the ASD relay, it sets a Diagnostic Trouble
Code (DTC).
BATTERY VOLTAGE—PCM INPUT
OPERATION
The PCM monitors the battery voltage input to
determine fuel injector pulse width and generator
field control.
If battery voltage is low the PCM will increase
injector pulse width (period of time that the injector
is energized).
BATTERY TEMPERATURE SENSOR—PCM
INPUT
OPERATION
The PCM uses the temperature of the battery area
to control the charge rate. The signal is used to reg-
ulate the system voltage. The system voltage is
higher at cold temperatures and is gradually reduced
as temperature around the battery increases.
FUEL SYSTEM 14 - 31