Chrysler 1998 Viper RT/10 Owner's Manual page 735

S R
FUEL SYSTEM 1 4 - 2 1
DESCRIPTION AND OPERATION ( C o n t i n u e d )
• Throttle Position Sensor
• Vehicle Speed Sensor
P C M O u t p u t s :
• A i r Conditioning W O T Relay
• Auto Shutdown (ASD) Relay
• Data L i n k Connector
• D u t y Cycle EVAP Canister Purge Solenoid
• EGR Solenoid
• Fuel Injectors
• Fuel Pump Relay
• Idle A i r Control Motor
• Ignition Coils
• Malfunction Indicator (Check Engine) Lamp
• Radiator Fan Relay
• Tachometer
Based on inputs i t receives, the P C M adjusts fuel
injector pulse w i d t h , idle speed, ignition spark
advance, ignition coil dwell and EVAP canister purge
operation. The P C M regulates the cooling fan, and
air conditioning. The P C M changes generator charge
rate by adjusting the generator field. The P C M also
performs diagnostics.
The P C M adjusts injector pulse w i d t h (air-fuel
ratio) based on the following inputs.
• Battery voltage
• Coolant temperature
• Intake air temperature
• Exhaust gas content (oxygen sensor)
• Engine speed (crankshaft position sensor)
• Manifold absolute pressure
• Throttle position
The P C M adjusts ignition t i m i n g based on the fol-
lowing inputs.
• Coolant temperature
• Intake air temperature
• Engine speed (crankshaft position sensor)
• Manifold absolute pressure
• Throttle position
The P C M also adjusts engine idle speed through
the idle air control motor based on the following
inputs.
• A i r conditioning sense
• Battery voltage
• Brake switch
• Coolant temperature
• Engine speed (crankshaft position sensor)
• Engine r u n time
• Manifold absolute pressure
• Throttle position
• Vehicle distance (speed)
The Auto Shutdown (ASD) and fuel pump relays
are mounted externally, but t u r n e d on and off by the
PCM.
The crankshaft position sensor signal is sent to the
PCM. I f the P C M does not receive the signal w i t h i n
approximately one second of engine cranking, i t deac-
tivates the A S D relay and fuel pump relay. When
these relays deactivate, power is shut off from the
fuel injectors, ignition coils, heating element i n the
oxygen sensors and the fuel pump.
The P C M contains a voltage converter t h a t
changes battery voltage to a regulated 5 volts direct
current to power the camshaft position sensor, crank-
shaft position sensor and vehicle speed sensor. The
P C M also provides a 5 volt direct current supply for
the manifold absolute pressure sensor and throttle
position sensor.
AIR CONDITIONING PRESSURE TRANSDUCER—
P C i INPUT
The Powertrain Control Module (PCM) monitors
the A/C compressor discharge (high side) pressure
through the air conditioning pressure transducer.
The transducer supplies an i n p u t to the P C M . The
P C M engages the A/C compressor clutch i f pressure
is sufficient for A/C system operation.
AUTOMATIC SHUTDOWN (ASD) SENSE—PCM
INPUT
The A S D sense circuit informs the P C M when the
ASD relay energizes. A 12 volt signal at this i n p u t
indicates to the P C M t h a t the ASD has been acti-
vated. This i n p u t is used only to sense t h a t the ASD
relay is energized.
When energized, the ASD relay supplies battery
voltage to the fuel injectors, ignition coils and the
heating element i n each oxygen sensor. I f the P C M
does not receive 12 volts from this i n p u t after
grounding the A S D relay, i t sets a Diagnostic Trouble
Code (DTC).
BATTERY VOLTAGE—PCM INPUT
The P C M monitors the battery voltage i n p u t to
determine fuel injector pulse w i d t h and generator
field control.
I f battery voltage is low the P C M w i l l increase
injector pulse w i d t h (period of time that the injector
is energized).
BRAKE SWITCH—PCM INPUT
When the brake switch is activated, the P C M
receives an i n p u t indicating that the brakes are
being applied. The brake switch is mounted on the
brake pedal support bracket.