Chrysler PT Cruiser 2001 Service Manual Supplement page 1112

PT
DESCRIPTION AND OPERATION (Continued)
NOTE: PCM Inputs:
• Air Conditioning Controls
• Battery Voltage
• Battery Temperature Sensor
• Brake Switch
• Camshaft Position Sensor
• Crankshaft Position Sensor
• CCD Bus
• Engine Coolant Temperature Sensor
• Fuel Level Sensor
• Ignition Switch
• Intake Air Temperature Sensor
• Knock Sensor (2.0/2.4L only)
• Leak Detection Pump
• Manifold Absolute Pressure (MAP) Sensor
• Oxygen Sensors
• Power Steering Pressure Switch
• SCI Receive
• Speed Control Switches
• Throttle Position Sensor
• Transmission Park/Neutral Switch (automatic
transmission)
• Vehicle Speed Sensor
NOTE: PCM Outputs:
• Air Conditioning Clutch Relay
• Auto Shutdown (ASD) Relay
• Charging Indicator Lamp
• CCD Bus
• SCI Transmit
• Proportional Purge Solenoid
• EGR Solenoid
• Fuel Injectors
• Fuel Pump Relay
• Generator Field
• Idle Air Control Motor
• Ignition Coils
• Malfunction Indicator (Check Engine) Lamp
• Radiator Fan Relays
• Speed Control Solenoids
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 and crankshaft posi-
tion 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
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.
PCM GROUND
OPERATION
Ground is provided through multiple pins of the
PCM connector. Depending on the vehicle there may
be as many as three different ground pins. There are
power grounds and sensor grounds.
The power grounds are used to control the ground
side of any relay, solenoid, ignition coil or injector.
The signal ground is used for any input that uses
FUEL SYSTEM 14 - 25
selection (park/neutral
selection (park/neutral