Chrysler 1991 - PARK;NEUTRAL SWITCH-ENGINE CONTROLLER INPUT; THROTTLE POSITION SENSOR (TPS)-ENGINE CONTROLLER INPUT; VEHICLE DISTANCE (SPEED) SENSOR -ENGINE CONTROLLER INPUT; WATER-IN-FUEL SENSOR -ENGINE CONTROLLER INPUT

FUEL SYSTEM 14 - 3
Fig. 3 Coolant Temperature Switch
automatic transmission housing. It provides an input
to the engine controller. The input indicates if the
automatic transmission is in Park, Neutral or a drive
gear selection.
If the transmission is in overdrive and the operator
shifts the vehicle into neutral and then back into
gear, the transmission will enter overdrive if the en-
gine controller determines all conditions are met.
The engine controller uses the park/neutral switch
input when determining speed control strategy. The
engine controller will disable speed control if the op-
erator shifts the transmission into neutral. The speed
control will have to be reset once the vehicle is
placed back into drive.
The park neutral switch is sometimes referred to
as the neutral safety switch. Refer to group 21
Transmissions, for adjustment, replacement, and test
information.
Fig. 4 Neutral Safety Switch
SPEEI CONTROL-ENGINE CONTROLLER INPUT
The engine controller regulates the speed control
system based on inputs it receives. The speed control
operating range is from 35 to 35 mph. Inputs that ef-
fect speed control operation are:
® park/neutral switch
© vehicle distance (speed) sensor
© throttle position sensor
THROTTLE POSITION SENSOR (TPS)—ENGINE
CONTROLLER INPUT
The throttle position sensor (TPS) is mounted on
the top of the fuel injection pump (Fig. 5). The TPS
provides an input to the engine controller. The input
ranges from approximately zero to five volts. The
sensor senses how far the throttle is open (past the
idle position). The engine controller uses the TPS in-
put when determining the 3-4 upshift (overdrive) and
the 4-3 downshift. Only vehicles with automatic
transmissions have a TPS.
The TPS is a potentiometer. The engine controller
supplies 5 volts to the sensor. TPS output to the en-
gine controller varies from approximately 1.0 volt at
idle to 3.5 volts at wide open throttle (WOT).
Fig. 5 Throttle Position Sensor
VEHICLE DISTANCE (SPEED) SENSOR —ENGINE
CONTROLLER INPUT
The distance sensor (Fig. 6) is located in the exten-
sion housing of the transmission. The engine control-
ler uses the TPS and distance sensor inputs to
determine when to shift into and out of overdrive.
The distance sensor is also used in determining
speed control set, decelerate, accelerate, maximum
set speed (85 mph), and minimum set speed (35 mph)
operations.
WATER-IN-FUEL SENSOR —ENGINE CONTROLLER
INPUT
The water-in-fuel (WIF) sensor is located at the
bottom of the fuel/water separator filter (Fig. 7). The
sensor sends an input to the engine controller when
it senses water in the fuel. The engine controller
looks at the water-in-fuel sensor signal when the