Dodge ram truck 3500 1996 Service Manual page 1270

D E S C R I P T I O N A N D O P E R A T I O N ( C o n t i n u e d )
OVERDRIVE/OVERRIDE SWITCH-PCM INPUT
On vehicles equipped with an automatic transmis­
sion and overdrive, the powertrain control module
(PCM) regulates the 3-4 overdrive up-shift and down­
shift through the overdrive solenoid. This solenoid is
located In the transmission. An overdrive/override
push-button switch is located on the instrument
panel.
The PCM circuit for overdrive is controlled by
Inputs from the engine coolant temperature sensor
and vehicle speed sensor. I f coolant temperature and
vehicle speed are not within the preset PCM specifi­
cations, the PCM will not allow the transmission to
shift into overdrive. These preset PCM specifications
must be met before the push-button switch will be
allowed to control overdrive operation.
The overdrive/override push-button switch is nor­
mally closed (overdrive allowed) when the lamp Is
not illuminated. I t opens (overdrive not allowed)
when the operator presses the switch and the lamp is
illuminated. The switch will revert to its normally
closed position (lamp off) each time the ignition
switch In turned on. The transmission downshifts i f
the operator presses the override switch while in
overdrive.
Refer to Group 21 for more transmission informa­
tion.
SPEED CONTROL SWITCH—PCM INPUT
Six different speed control functions, using three
momentary contact switches, are monitored through
this multiplexed input. The resistance monitored at
this input, in combination with the length of time the
PCM measures the resistance, determines which
switch feature has been selected. The three switches
are: On/Off, Set/Coast and Resume/Accelerate.
Refer to Group 8H, Vehicle Speed Control System
for further speed control information.
TRANSMISSION PARK/NEUTRAL SWITCH—PCM
INPUT
The park/neutral switch Is located on the transmis­
sion housing and provides an input to the powertrain
control module (PCM). This will indicate that the
automatic transmission is in Park, Neutral or a drive
gear selection. This input is used to determine idle
speed (varying with gear selection), fuel Injector
pulse width, ignition timing advance and vehicle
speed control operation. Refer to Group 21, Transmis­
sions, for testing, replacement and adjustment infor­
mation.
TRANSMISSION GOVERNOR PRESSURE
SENSOR—PCM INPUT
Provides a signal proportional to the transmission
governor pressure. I t provides feedback for control of
the variable force solenoid, which regulates transmis­
sion governor pressure. This input is used with
4-speed electronic transmissions only.
TRANSMISSION TEMPERATURE SENSOR—PCM
INPUT
This input is used in the shift operation for
4-speed electronic transmissions only. The tempera­
ture data is used for: torque converter clutch opera­
tion, overdrive shift, low temperature shift
compensation, wide open throttle shift strategy and
governor pressure transducer calibration.
TRANSMISSION PRESSURE SENSOR—PCM INPUT
Provides a signal proportional to the transmission
governor pressure. I t provides feedback for control of
the variable force solenoid, which regulates transmis­
sion governor pressure. This is used with 4-speed
automatic transmissions only.
THROTTLE POSITION SENSOR (TPS)—3.9L/5.2L/
5.9L ENGINES—PCM INPUT
The throttle position sensor (TPS) is mounted on
the throttle body (Fig. 15). The TPS is a variable
resistor that provides the powertrain control module
(PCM) with an input signal (voltage) that represents
throttle blade position. The sensor is connected to the
throttle blade shaft. As the position of the throttle
blade changes, the resistance of the TPS changes.
The PCM supplies approximately 5 volts to the
TPS. The TPS output voltage (input signal to the
PCM) represents the throttle blade position. The
PCM receives an input signal voltage from the TPS.
This will vary in an approximate range of from 1 volt
at minimum throttle opening (idle), to 4 volts at wide
open throttle. Along with inputs from other sensors,
the PCM uses the TPS input to determine current
engine operating conditions. I n response to engine
operating conditions, the PCM will adjust fuel injec­
tor pulse width and ignition timing.
THROTTLE POSITION SENSOR (TPS)—8.0L
ENGINE—PCM INPUT
The throttle position sensor (TPS) is mounted on
the throttle body (Fig. 17). The TPS is a variable
resistor that provides the powertrain control module
(PCM) with an input signal (voltage) that represents
throttle blade position. The sensor is connected to the
throttle blade shaft. As the position of the throttle
blade changes, the resistance of the TPS changes.
The PCM supplies approximately 5 volts to the
TPS. The TPS output voltage (input signal to the
PCM) represents the throttle blade position. The
PCM receives an input signal voltage from the TPS.
This will vary in an approximate range of from 1 volt
at minimum throttle opening (idle), to 4 volts at wide