cruise control DODGE TRUCK 1993 Service Repair Manual

14 - 38
FUEL SYSTEM

•
Fig.
17 Ignition Coil—5.9L
HDC-Gas
Engine

SHIFT INDICATOR-PCM
OUTPUT
Vehicles equipped with manual transmissions have
an Up-Shift indicator lamp. The lamp is controlled
by the powertrain control module (PCM). The lamp illuminates on the instrument panel to indicate when
the driver should shift to the next highest gear for
best fuel economy. The PCM will turn the lamp off after 3 to 5 seconds if the shift of gears is not per­
formed. The up-shift light will remain off until vehi­ cle stops accelerating and is brought back to range of
up-shift light operation. This will also happen if ve­
hicle is shifted into fifth gear. The indicator lamp is normally illuminated when
the ignition switch is turned on and it is turned off
when the engine is started up. With the engine run­
ning, the lamp is turned on/off depending upon en­
gine speed and load.

SPEED
CONTROL-PCM
OUTPUT
Speed control operation is regulated by the power-
train control module (PCM). The PCM controls the
vacuum to the throttle actuator through the speed
control vacuum and vent solenoids. Refer to Group
8H for Speed Control Information.

TACHOMETER—PCM
OUTPUT
The powertrain control module (PCM) supplies en­
gine rpm values to the instrument cluster tachome­ ter. Refer to Group 8E for tachometer information.

OPEN
LOOP/CLOSED LOOP MODES
OF

OPERATION

As input signals to the powertrain control module
(PCM) change, the PCM adjusts its response to the
output devices. For example, the PCM must calculate
different injector pulse width and ignition timing for
idle than it does for wide open throttle (WOT). There
are several different modes of operation that deter­
mine how the PCM responds to the various input sig­
nals.
MODES

• Open Loop
• Closed Loop During Open Loop modes, the powertrain control
module (PCM) receives input signals and responds
only according to preset PCM programming. Input
from the oxygen (02) sensor(s) is not monitored dur­
ing Open Loop modes.
During Closed Loop modes, the PCM will monitor
the oxygen (02) sensor input. This input indicates to
the PCM whether or not the calculated injector pulse width results in the ideal air-fuel ratio. This ratio is 14.7 parts air-to-1 part fuel. By monitoring the ex­
haust oxygen content through the 02 sensor, the
PCM can fine tune the injector pulse width. This is done to achieve optimum fuel economy combined
with low emission engine performance.
The fuel injection system has the following modes
of operation:
• Ignition switch ON • Engine start-up (crank)
• Engine warm-up
• Idle
• Cruise • Acceleration
• Deceleration
• Wide open throttle (WOT)
• Ignition switch OFF The ignition switch On, engine start-up (crank),
engine warm-up, acceleration, deceleration and wide
open throttle modes are Open Loop modes. The idle and cruise modes, (with the engine at operating tem­
perature) are Closed Loop modes.

IGNITION
SWITCH
(KEY-ON)
MODE
This is an Open Loop mode. When the fuel system
is activated by the ignition switch, the following ac­
tions occur:
• The powertrain control module (PCM) pre-posi-
tions the idle air control (IAC) motor. • The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel strategy.
• The PCM monitors the engine coolant temperature sensor input. The PCM modifies fuel strategy based
on this input.
• Intake manifold charge air temperature sensor in­
put is monitored.
• Throttle position sensor (TPS) is monitored. • The auto shut down (ASD) relay is energized by
the PCM for approximately three seconds. • The fuel pump is energized through the fuel pump
relay by the PCM. The fuel pump will operate for ap­
proximately one second unless the engine is operat­ ing or the starter motor is engaged.
• The 02 sensor(s) heater element is energized
through the fuel pump relay. The 02 sensor(s) input

•

FUEL SYSTEM
14 - 39 is not used by the PCM to calibrate air-fuel ratio
during this mode of operation,
• The up-shift indicator light is illuminated (manual
transmission only).
ENGINE
START-UP
MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The powertrain control module (PCM) receives in­
puts from:
• Battery voltage
• Engine coolant temperature sensor • Crankshaft position sensor
• Intake manifold charge air temperature sensor • Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Starter motor relay • Camshaft position sensor signal The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position sensor signal within 3 seconds of cranking the en­

gine,
it will shut down the fuel injection system.
The fuel pump is activated by the PCM through
the fuel pump relay.
Voltage is applied to the fuel injectors with the
PCM. The PCM will then control the injection se­ quence and injector pulse width by turning the
ground circuit to each individual injector on and off.
The PCM determines the proper ignition timing ac­
cording to input received from the crankshaft posi­
tion sensor.
ENGINE
WARM-UP
MODE This is an Open Loop mode. During engine warm-

up,
the powertrain control module (PCM) receives in­
puts from:
• Battery voltage • Crankshaft position sensor
• Engine coolant temperature sensor
• Intake manifold charge air temperature sensor • Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS) • Camshaft position sensor signal (in the distributor)
• Park/Neutral switch (gear indicator signal—auto,

trans,
only)
• Air conditioning select signal (if equipped)
• Air conditioning request signal (if equipped) Based on these inputs the following occurs:
• Voltage is applied to the fuel injectors with the
powertrain control module (PCM). The PCM will
then control the injection sequence and injector pulse
width by turning the ground circuit to each individ­ ual injector on and off.
• The PCM adjusts engine idle speed through the
idle air control (IAC) motor and adjusts ignition tim­
ing. • The PCM operates the A/C compressor clutch
through the clutch relay. This is done if A/C has
been selected by the vehicle operator and requested by the A/C thermostat.
• If the vehicle has a manual transmission, the up­
shift light is operated by the PCM.
« When engine has reached operating temperature,
the PCM will begin monitoring 02 sensor(s) input.
The system will then leave the warm-up mode and go into closed loop operation.

IDLE
MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At idle speed, the powertrain control module (PCM) receives inputs from:
Air conditioning select signal (if equipped)
• Air conditioning request signal (if equipped)
• Battery voltage
• Crankshaft position sensor
• Engine coolant temperature sensor • Intake manifold charge air temperature sensor
• Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Camshaft position sensor signal (in the distributor)
® Battery voltage
• Park/Neutral switch (gear indicator signal—Auto,

trans,
only) • Oxygen sensor
Based on these inputs, the following occurs:
• Voltage is applied to the fuel injectors with the
powertrain control module (PCM). The PCM will
then control injection sequence and injector pulse
width by turning the ground circuit to each individ­ ual injector on and off.
• The PCM monitors the 02 sensor(s) input and ad­
justs air-fuel ratio by varying injector pulse width. It also adjusts engine idle speed through the idle air
control (IAC) motor. • The PCM adjusts ignition timing by increasing and decreasing spark advance.
• The PCM operates the A/C compressor clutch
through the clutch relay. This happens if A/C has
been selected by the vehicle operator and requested
by the A/C thermostat.

CRUISE
MODE
When the engine is at operating temperature, this
is a Closed Loop mode. At cruising speed, the power-
train control module (PCM) receives inputs from:
• Air conditioning select signal (if equipped)
• Air conditioning request signal (if equipped)
• Battery voltage • Engine coolant temperature sensor
• Crankshaft position sensor
• Intake manifold charge air temperature sensor • Manifold absolute pressure (MAP) sensor
• Throttle position sensor (TPS)
• Camshaft position sensor signal (in the distributor)

•

FUEL
SYSTEM
14-45 (12) Inspect accelerator cable, transmission throt­
tle cable (if equipped) and cruise control cable con­
nections (if equipped). Check their connections to the
throttle arm of throttle body for any binding or re­ strictions (Fig. 8).

Fig.
8
Throttle
Body
Cables—Typical
(13) If equipped with vacuum brake booster, verify
that vacuum booster hose is firmly connected to fit­
ting on intake manifold. Also check connection to
brake vacuum booster.
(14) Inspect the air cleaner inlet and air filter ele­
ment for dirt or restrictions.
(15) Inspect radiator grille area, radiator fins and
air conditioning condenser for restrictions. (16) Verify that the intake manifold charge air
temperature sensor wire connector is firmly con­ nected to harness connector (Figs. 9 or 10).

Fig.
9 Air
Temperature
Sensor—3.9L
(V-6)
Engine
(17) Verify that MAP sensor electrical connector is
firmly connected to MAP sensor (Fig. 11). Also verify
that rubber L-shaped fitting from MAP sensor to the
throttle body is firmly connected (Fig. 12).
(18) Verify that fuel injector wire harness connec­
tors are firmly connected to injectors in the correct
Fig.
10 Air
Temperature
Sensor—5.2U5.9L
(V-8)

Engines
MANIFOLD
ABSOLUTE

Fig.
11 MAP Sensor—Typical
order. Each harness connector is numerically tagged
with the injector number (INJ 1, INJ 2 etc.) of its
corresponding fuel injector and cylinder number.
(19) Verify harness connectors are firmly con­
nected to idle air control (IAC) motor, throttle posi­
tion sensor (TPS) and manifold absolute pressure (MAP) sensor (Fig. 11).
(20) Verify that wire harness connector is firmly
connected to the engine coolant temperature sensor (Fig. 13).
(21) Raise and support the vehicle.
(22) Verify that oxygen sensor wire connector (or
connectors) are firmly connected to the sensor (or sensors). Inspect sensor(s) and connector(s) for dam­age (Figs. 14 or 15).

•

FUEL
SYSTEM
14 - 87
ENGINE
WARM-UP

• The PCM may start the air intake heater post-heat
cycle depending on intake air temperature. If manifold air temperature was at or below 15°C (59°F) when the
ignition switch was turned on, the cycle is started.
• If intake manifold air temperature is below 32°C
(90°F),
the KSB solenoid will be energized through
the air temperature switch. The solenoid remains en­ ergized until the air temperature switch opens. The
switch opens when intake manifold air temperature
is above 32°C (90°F).
• If the coolant temperature is below 16°C (60° F),
the transmission will not be allowed to enter over­ drive (automatic transmission).
• The PCM will turn on the water-in-fuel lamp if a signal is received from the water-in-fuel sensor.

CRUISE
OR
IDLE

• The PCM monitors intake manifold air tempera­
ture through the charge temperature sensor input. • If intake manifold air temperature is below 32°C
(90°F),
the KSB solenoid will be energized through
the air temperature switch. The solenoid remains en­ ergized until the air temperature switch opens. The switch opens when intake manifold air temperature
is above 32°C (90°F).
• The air intake heater post-heat cycle will be com­
pleted, if it is not already over.
• The vehicle speed sensor, engine speed sensor and
throttle position sensor inputs are used to control
transmission overdrive operation.
• If the coolant temperature is below 16° C (60° F),
the transmission will not be allowed to enter over­ drive (automatic transmission).
• If the transmission thermo-switch is open, the
transmission will not be allowed to enter into over­
drive (automatic transmission). If the switch opens
when the vehicle is in overdrive, the transmission
will be downshifted. The transmission thermo-switch opens at 134°C (273°F).
• The thermo-switch will close once the transmission
fluid temperature drops to 116°C (240°F). • The PCM will turn on the water-in-fuel lamp if a signal is received from the water-in-fuel sensor.

ACCELERATION
• The vehicle speed sensor, engine speed sensor and
throttle position sensor inputs are used to control
transmission overdrive operation.
• If the coolant temperature is below 16° C (60° F),
the transmission will not be allowed to enter over­
drive (automatic transmission).
• If intake manifold air temperature is below 32°C
(90°F),
the KSB solenoid will be energized through
the air temperature switch. The solenoid remains en­ ergized until the air temperature switch opens. The
switch opens when intake manifold air temperature
is above 32°C (90°F). • If the transmission thermo-switch is open, the
transmission will not be allowed to enter into over­
drive (automatic transmission). If the switch opens
when the vehicle is in overdrive, the transmission
will be downshifted. The transmission thermo-switch opens at 134°C (273°F). The thermo-switch will close
once the transmission fluid temperature drops to 116°C (240°F).
• The PCM will turn on the water-in-fuel lamp if a
signal is received from the water-in-fuel sensor.
• If the speed control system resume/accelerate func­
tion is being used, the PCM will only allow the vehi­
cle to accelerate at a predetermined rate. If a speed
control has been set and the resume/accelerate but­
ton is momentarily pushed in, the PCM will increase
vehicle speed by two miles per hour.
• If the brakes are applied, the PCM will disable the
speed control.

DECELERATION

• The vehicle speed sensor, engine speed sensor and
throttle position sensor inputs are used to control
transmission overdrive operation.
• If the coolant temperature is below 16° C (60° F),
the transmission will not be allowed to enter over­ drive (automatic transmission).
• If the transmission thermo-switch is open, the trans­
mission will not be allowed to enter into overdrive (au­
tomatic transmission). If the switch opens when the
vehicle is in overdrive, the transmission will be down­ shifted. The transmission thermo-switch opens at 134°C (273°F). The thermo-switch will close once the transmis­
sion fluid temperature drops to 116°C (240°F).
• The PCM will turn on the water-in-fuel lamp if a
signal is received from the water-in-fuel sensor.
• If intake manifold air temperature is below 32°C
(90°F),
the KSB solenoid will be energized through
the air temperature switch. The solenoid remains en­ ergized until the air temperature switch opens. The
switch opens when intake manifold air temperature
is above 32°C (90°F).
• If the speed control system coast/set function is be­
ing used, the PCM will only allow the vehicle to de­ celerate at a predetermined rate. If the coast/set
switch is pushed while the system is operating, the
PCM will set speed control to the rate the vehicle is
traveling at when the switch is released. • If the brakes are applied, the PCM will disable the speed control.

IGNITION SWITCH
OFF
• When the ignition switch is turned to the off posi­
tion, the PCM still receives battery voltage through
the battery input. Battery voltage is needed to keep
PCM memory alive. The PCM memory stores diag­ nostic trouble code (DTC) messages and the mini­
mum TPS value from the previous key-on.

2i
- 4
EMISSION
CONTROL
SYSTEMS

•
VACUUM
HOSE
ROUTING
SCHEMATICS

The following vacuum hose routing schematics
are used
as
examples only.
If
there
are any
differ­
ences between these schematics
and the
Vehicle
Emission Control Information (VECI) label schemat­

ics,
those shown
on the
VECI label should
be
used.
ENGINE
VACUUM
SCHEMATIC-3.9U5.2L/5.9L
LDC
ENGINES

TO ATMOSPHERE
i
TRANSDUCER

FUEL
TANK

PRESSURE
RELIEF
ROLLOVER VALVE

W/ORIFICE

EVAP
CANISTER
TO CLIMATE CONTROL,
CRUISE
CONTROL,
4WD
AXLE

(WHEN
EQUIPPED) INTAKE
MANIFOLD
ORIFICE ENGINE
VALVE
COVER FUEL PRESSURE
REGULATOR
M

P
= MANIFOLD VACUUM
= PORTED VACUUM

"8^
EGR
VALVE
EVAP PURGE SOLENOID MAP

SENSOR

CHECK VALVE W/ORIFICE
CRANKCASE

BREATHER
TO
AIR
CLEANER
ENGINE VALVE
COVER TO BRAKE
BOOSTER FRONT
OF
VEHICLE
J9325-13