Dodge ram truck 3500 1996 Service Manual page 1271

BR
FUEL SYSTEM 14 - 37
DESCRIPTION AND OPERATION (Continued)
Fig. 17 Sensor Location—8.0L Engine
open throttle. Along with inputs from other sensors,
the PCM uses the TPS input to determine current
engine operating conditions. In response to engine
operating conditions, the PCM will adjust fuel Injec­
tor pulse width and ignition timing.
VEHICLE SPEED AND DISTANCE SENSOR—PCM
INPUT
The vehicle speed sensor is located on the speed­
ometer pinion gear adapter (Fig. 18). The pinion gear
adapter is located on the extension housing of the
transmission (drivers side). The sensor input is used
by the powertrain control module (PCM) to deter­
mine vehicle speed and distance traveled.
SENSOR
ELECTRICAL
CONNECTOR
J9414-60
Fig. 18 Vehicle Speed Sensor Location—Typical
The speed sensor generates 8 pulses per sensor
revolution. These signals, in conjunction with a
closed throttle signal from the throttle position sen­
sor, indicate a closed throttle deceleration to the
PCM. When the vehicle is stopped at idle, a closed
throttle signal is received by the PCM (but a speed
sensor signal is not received).
Under deceleration conditions, the PCM adjusts
the idle air control (IAC) motor to maintain a desired
MAP value. Under idle conditions, the PCM adjusts
the IAC motor to maintain a desired engine speed.
POWER GROUND
The power ground is used to control ground cir­
cuits for the following powertrain control module
(PCM) loads:
• Generator field winding
• 8 volt (PCM) power supply
• Fuel injectors
• Ignition coil
AIR CONDITIONING (A/C) CLUTCH RELAY—PCM
OUTPUT
The A/C relay is located in the Power Distribution
Center (PDC) (Fig. 19). Refer to label on PDC cover
for relay location.
Fig. 19 Power Distribution Center (PDC)
The powertrain control module (PCM) activates the
A/C compressor through the A/C clutch relay. The
PCM regulates A/C compressor operation by switch­
ing the ground circuit for the A/C clutch relay on and
off.
When the PCM receives a request for A/C from A/C
evaporator switch, i t will adjust idle air control (IAC)
motor position. This is done to increase idle speed.
The PCM will then activate the A/C clutch through
the A/C clutch relay. The PCM adjusts idle air control
(IAC) stepper motor position to compensate for
increased engine load from the A/C compressor.