Dodge RAM TRUCK 1500 1995 Service Manual page 1128

14 - 46 COMPONENT DESCRIPTION/SYSTEM OPERATION—EXCEPT DIESEL
SENSOR
ELECTRICAL
CONNECTOR
J9414-60
Fig. 33 Vehicle Speed Sensor—Typical
SPEED CONTROL—PCM PINS #48, #49 AND
#50—PCM INPUT
The speed control system provides three separate
inputs to the powertrain control module (PCM); On/
Off, Set and Resume. The On/Off input informs the
PCM that the speed control system has been acti­
vated. The Set input informs the PCM that a fixed
vehicle speed has been selected. The Resume input
indicates to the PCM that the previous fixed speed is
requested.
The speed control operating range is from 50 km/h
to 142 km/h (35 to 85 mph). Inputs that effect speed
control operation are:
® Brake switch position
• Park/neutral switch
© Vehicle speed sensor
® Throttle position sensor
Refer to Group 8H for further speed control infor­
mation.
AUTOMATIC SHUTDOWN (ASD) RELAY—PCM PIN
#51—PCM OUTPUT
This circuit (pin #51) controls operation of both the
ASD and fuel pump relays.
The ASD relay is located in the power distribution
center (PDC). The PDC is located next to the battery
in the engine compartment (Fig. 34). For the location
of the relay within the PDC, refer to PDC cover.
The ASD relay, after receiving signals from the
crankshaft and camshaft position sensors, will supply
battery voltage to the fuel injectors, ignition coil(s)
and generator field winding. If these signals are not
Fig. 34 Power Distribution Center (PDC) Location
received by the PCM after approximately one second
of engine cranking (start-up), the ASD relay will be
shut down.
The ground circuit for the coil in the ASD relay is
controlled by the powertrain control module (PCM).
The PCM operates the relay by switching the ground
circuit ON and OFF.
Also refer to Fuel Pump Relay—PCM Pin
#51—PCM Output for additional information.
FUEL PUMP RELAY—PCM PIN #51—PCM
OUTPUT
The PCM energizes the electric fuel pump and the
oxygen sensor (02S) heating element through the
fuel pump relay. Battery voltage is applied to the fuel
pump relay when the ignition key is ON. The relay is
energized when a ground signal is provided by pin
#51 on the PCM.
Refer to Automatic Shutdown Relay—PCM Pin
#51—PCM Output for additional information.
The fuel pump will operate for approximately one
second unless the engine is operating or the starter
motor is engaged.
The fuel pump relay is located in the power distri­
bution center (PDC). The PDC is located next to the
battery in the engine compartment (Fig. 34). For the
location of the relay within the PDC, refer to PDC
cover.
EVAP CANISTER PURGE SOLENOID—PCM PIN
#52—PCM OUTPUT
This circuit controls a ground signal for operation
of the EVAP Canister Purge Solenoid.
Refer to Group 25, Emission Control System. See
EVAP Canister Purge Solenoid.