Sensor Return—Pcm Input; Signal Ground—Pcm Input; Throttle Position Sensor (Tps)—Pcm - Dodge 2000 DURANGO Service Manual

14 - 36 FUEL SYSTEM
DESCRIPTION AND OPERATION (Continued)
OPERATION
The power steering pressure switch provides an
input to the Powertrain Control Module (PCM). This
input is provided during periods of high pump load
and low engine rpm; such as during parking maneu-
vers. The PCM will then increase the idle speed
through the Idle Air Control (IAC) motor. This is
done to prevent the engine from stalling under the
increased load.
When steering pump pressure exceeds 3275 kPa
690 kPa (475 psi
switch will open and the PCM will increase the
engine idle speed. This will prevent the engine from
stalling.
When pump pressure drops to approximately 1379
kPa (200 psi), the switch circuit will re-close and
engine idle speed will return to its previous setting.
SENSOR RETURN—PCM INPUT
OPERATION
The Sensor Return circuits are internal to the Pow-
ertrain Control Module (PCM).
Sensor Return provides a low–noise ground refer-
ence for all engine control system sensors. Refer to
Power Grounds for more information.
SIGNAL GROUND—PCM INPUT
OPERATION
Signal ground provides a low noise ground to the
data link connector.
THROTTLE POSITION SENSOR (TPS)—PCM
INPUT
DESCRIPTION
The 3–wire Throttle Position Sensor (TPS) is
mounted on the throttle body and is connected to the
throttle blade.
OPERATION
The TPS is a 3–wire variable resistor that provides
the Powertrain Control Module (PCM) with an input
signal (voltage) that represents the throttle blade
position of the throttle body. The sensor is connected
to the throttle blade shaft. As the position of the
throttle blade changes, the resistance (output volt-
age) 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.26
volts at minimum throttle opening (idle), to 4.49 volts
at wide open throttle. Along with inputs from other
100 psi), the normally closed
sensors, the PCM uses the TPS input to determine
current engine operating conditions. In response to
engine operating conditions, the PCM will adjust fuel
injector pulse width and ignition timing.
The PCM needs to identify the actions and position
of the throttle blade at all times. This information is
needed to assist in performing the following calcula-
tions:
• Ignition timing advance
• Fuel injection pulse-width
• Idle (learned value or minimum TPS)
• Off-idle (0.06 volt)
• Wide Open Throttle (WOT) open loop (2.608
volts above learned idle voltage)
• Deceleration fuel lean out
• Fuel cutoff during cranking at WOT (2.608 volts
above learned idle voltage)
• A/C WOT cutoff (certain automatic transmis-
sions only)
VEHICLE SPEED AND DISTANCE—PCM INPUT
OPERATION
Vehicle speed and distance covered are measured
by the Rear Wheel Speed Sensor. The sensor is
mounted to the rear axle. A signal is sent from this
sensor to the Controller Antilock Brake (CAB) com-
puter. A signal is then sent from the CAB to the Pow-
ertrain Control Module (PCM) to determine vehicle
speed and distance covered. The PCM will then
determine strategies for fuel system and speed con-
trol system operation.
Refer to Odometer and Trip Odometer in Group
8E, Instrument Panel for additional information.
AUTO SHUTDOWN (ASD) RELAY—PCM
OUTPUT
DESCRIPTION
The 5–pin, 12–volt, Automatic Shutdown (ASD)
relay is located in the Power Distribution Center
(PDC). Refer to label on PDC cover for relay location.
OPERATION
The ASD relay supplies battery voltage (12+ volts)
to the fuel injectors and ignition coil(s). With certain
emissions packages it also supplies 12–volts to the
oxygen sensor heating elements.
The ground circuit for the coil within the ASD
relay is controlled by the Powertrain Control Module
(PCM). The PCM operates the ASD relay by switch-
ing its ground circuit on and off.
The ASD relay will be shut–down, meaning the
12–volt power supply to the ASD relay will be de-ac-
tivated by the PCM if:
DN