Chrysler Town & Country/Voyager, Dodge Caravan, Plymouth Voyager. Manual — part 26
(3) Remove engine controller mounting screws (Fig.
17).
(4) Remove electrical connector from engine control-
ler. Remove engine controller.
(5) Reverse the above procedure for installation.
OXYGEN SENSOR (O
2
SENSOR)
The oxygen sensor is installed in the exhaust mani-
fold (Fig. 18).
CAUTION: Do not pull on the oxygen sensor wire
when disconnecting the electrical connector.
WARNING: THE EXHAUST MANIFOLD MAY BE EX-
TREMELY HOT. USE CARE WHEN SERVICING THE
OXYGEN SENSOR.
(1) Disconnect oxygen sensor electrical connector
(Fig. 19).
(2) Remove sensor using Tool C-4907 (Fig. 20).
Fig. 16 Canister Purge Solenoid
Fig. 17 Engine Controller
Fig. 18 Heated Oxygen Sensor
Fig. 19 Oxygen Sensor Electrical Connection
Fig. 20 Oxygen Sensor Socket
.
FUEL SYSTEM
14 - 51
When the sensor is removed, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E tap.
If using original sensor, coat the threads with Loctite
771-64 anti-seize compound or equivalent. New sen-
sors are packaged with compound on the threads and
no additional compound is required. The sensor must
be tightened to 27 N
Im (20 ft. lbs.) torque.
3.0L MULTI-POINT FUEL INJECTION—SYSTEM OPERATION
INDEX
page
page
Air Conditioning (A/C) Clutch Relay—Engine
Controller Output
. . . . . . . . . . . . . . . . . . . . . . . . . 57
Air Conditioning Switch Sense—Engine Controller
Input
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Alternator Field—Engine Controller Output
. . . . . . 57
Auto Shutdown (ASD) Relay and Fuel Pump
Relay—Engine Controller Output
. . . . . . . . . . . . 57
Automatic Idle Speed (AIS) Motor—Engine
Controller Output . . . . . . . . . . . . . . . . . . . . . . . . 58
Battery Voltage—Engine Controller Input . . . . . . . . 54
Brake Switch—Engine Controller Input
. . . . . . . . . 54
Canister Purge Solenoid—Engine Controller
Output
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Ccd Bus
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Check Engine Lamp—Engine Controller Output
. . 59
Coolant Temperature Sensor—Engine Controller
Input
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Diagnostic Connector—Engine Controller Output
. . 59
Distributor Pick-Up—Engine Controller Input
. . . . . 54
Electronic Automatic Transmission Controller—
Engine Controller Output
. . . . . . . . . . . . . . . . . . 59
Emission Maintenance Reminder (EMR) Lamp—
Engine Controller Output
. . . . . . . . . . . . . . . . . . 59
Engine Controller
. . . . . . . . . . . . . . . . . . . . . . . . . 53
Engine Controller Reprogramming (Flash)
. . . . . . . 54
Fuel Injectors—Engine Controller Output . . . . . . . . 59
Fuel Pressure Regulator . . . . . . . . . . . . . . . . . . . . 62
Fuel Supply Circuit
. . . . . . . . . . . . . . . . . . . . . . . . 62
General Information
. . . . . . . . . . . . . . . . . . . . . . . 52
Ignition Coil—Engine Controller Output
. . . . . . . . . 60
Manifold Absolute Pressure (MAP) Sensor—
Engine Controller Input
. . . . . . . . . . . . . . . . . . . 55
Modes of Operation
. . . . . . . . . . . . . . . . . . . . . . . 60
Oxygen Sensor (O
2
Sensor)—Engine Controller
Input
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Part Throttle Unlock Solenoid—Engine Controller
Output
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Radiator Fan Relay—Engine Controller Output
. . . 60
Speed Control Solenoids—Engine Controller
Output
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Speed Control—Engine Controller Input
. . . . . . . . 56
Tachometer—Engine Controller Output
. . . . . . . . . 60
Throttle Body
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Throttle Position Sensor (TPS)—Engine Controller
Input
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Transmission Park/Neutral Switch—Engine
Controller Input
. . . . . . . . . . . . . . . . . . . . . . . . . 56
Vehicle Distance (Speed) Sensor—Engine
Controller Input
. . . . . . . . . . . . . . . . . . . . . . . . . 57
GENERAL INFORMATION
The 3.0L engine uses a sequential Multi-point Elec-
tronic Fuel Injection system (Fig. 1). The MPI system is
computer regulated and provides precise air/fuel ratios
for all driving conditions.
The MPI system is operated by the Single Board
Engine Controller II (SBEC II), referred to in this
manual as the engine controller.
The engine controller regulates ignition timing, air-
fuel ratio, emission control devices, cooling fan, charg-
ing system, idle speed and speed control. Various
sensors provide the inputs necessary for the engine
controller to correctly operate these systems. In addi-
tion to the sensors, various switches also provide
inputs to the engine controller.
All inputs to the engine controller are converted into
signals. The engine controller can adapt its program-
ming to meet changing operating conditions.
Fuel is injected into the intake port above the intake
valve in precise metered amounts through electrically
operated injectors. The engine controller fires the in-
jectors in a specific sequence. The controller maintains
an air fuel ratio of 14.7 parts air to 1 part fuel by
constantly adjusting injector pulse width. Injector
pulse width is the length of time the injector is open.
The engine controller adjusts injector pulse width by
opening and closing the ground path to the injector.
Engine RPM (speed) and manifold absolute pressure
(air density) are the primary inputs that determine
injector pulse width.
SYSTEM DIAGNOSIS
The engine controller tests many of its own input and
output circuits. If a fault is found in a circuit, the
information is stored in the memory. Fault codes can
displayed using the Check Engine lamp. Also, the
technician can obtain the fault description by connect-
ing the DRB II to the vehicle.
CCD BUS
Various controllers and modules exchange informa-
tion through a communications port called the CCD
Bus. The engine controller transmits the check en-
14 - 52
FUEL SYSTEM
.
gine lamp On/Off signal, engine RPM and vehicle load
data on the CCD Bus.
ENGINE CONTROLLER
The engine controller is a digital computer contain-
ing a microprocessor (Fig. 2). The controller receives
input signals from various switches and sensors that
are referred to as Engine Controller Inputs. Based on
these inputs, the controller adjusts various engine and
vehicle operations through devices that are referred to
as Engine Controller Outputs.
Engine Controller Inputs:
• Air Conditioning Controls
• Battery Voltage
• Brake Switch
• Coolant Temperature Sensor
• Distributor Pick-up
• Manifold Absolute Pressure (MAP) Sensor
• Oxygen Sensor
• SCI Receive
• Speed Control System Controls
• Throttle Position Sensor
• Park/Neutral Switch (automatic transmission)
• Vehicle Distance (Speed) Sensor
Engine Controller Outputs:
• Air Conditioning Clutch Relay
• Alternator Field
• Automatic Idle Speed (AIS) Motor
• Auto Shutdown (ASD) and Fuel Pump Relays
• Canister Purge Solenoid
• Check Engine Lamp
• Diagnostic Connector
• Electric EGR Transducer (EET)
• Emission Maintenance Reminder (EMR) Lamp
• Fuel Injectors
• Ignition Coil
• Part Throttle Unlock (PTU) Solenoid
• Radiator Fan Relay
• Speed Control Solenoids
Fig. 1 Multi-Point Fuel Injection Components
Fig. 2 Engine Controller
.
FUEL SYSTEM
14 - 53
• Tachometer Output
Based on inputs it receives, the engine controller
adjusts fuel injector pulse width, idle speed, ignition
spark advance, ignition coil dwell and canister purge
operation. The engine controller regulates the cooling
fan, air conditioning and speed control systems. The
controller changes alternator charge rate by adjusting
the alternator field.
The engine controller adjusts injector pulse width
(air-fuel ratio) based on the following inputs.
• battery voltage
• coolant temperature
• exhaust gas content
• engine speed (distributor pick-up)
• manifold absolute pressure
• throttle position
The engine controller adjusts ignition timing based
on the following inputs.
• coolant temperature
• engine speed (distributor pick-up)
• manifold absolute pressure
• throttle position
The Automatic Shut Down (ASD) and Fuel Pump
relays are mounted externally, but turned on and off by
the engine controller through the same circuit.
The distributor pick-up signal is sent to the engine
controller. If the engine controller does not receive a
distributor signal within approximately one second of
engine cranking, the ASD relay and fuel pump relay
are deactivated. When these relays are deactivated,
power is shut off to the fuel injector, ignition coil,
oxygen sensor heating element and fuel pump.
The engine controller contains a voltage converter
that changes battery voltage to a regulated 9.0 volts to
power the distributor pick-up and vehicle speed sensor.
The controller also provides a 5.0 volts supply for the
manifold absolute pressure sensor and throttle posi-
tion sensor.
AIR CONDITIONING SWITCH SENSE—ENGINE
CONTROLLER INPUT
When the air conditioning or defrost switch is in the
ON position and the low pressure, high pressure and
ambient temperature switches are closed, the control-
ler receives an input for air conditioning. After receiv-
ing this input, the engine controller activates the A/C
compressor clutch by grounding the A/C clutch relay.
The engine controller also adjusts idle speed to a
scheduled RPM to compensate for increased engine
load.
BATTERY VOLTAGE—ENGINE CONTROLLER INPUT
The engine controller monitors the battery voltage
input to determine fuel injector pulse width and alter-
nator field control.
If battery voltage is low the engine controller will
increase injector pulse width (period of time that the
injector is energized).
BRAKE SWITCH—ENGINE CONTROLLER INPUT
When the brake switch is activated, the engine
controller receives an input indicating that the brakes
are being applied. After receiving this input the engine
controller maintains idle speed to a scheduled RPM
through control of the Automatic Idle Speed Motor. The
brake switch is mounted on the brake pedal support
bracket.
COOLANT TEMPERATURE SENSOR—ENGINE CON-
TROLLER INPUT
The coolant temperature sensor is a variable resistor
with a range of -40°F to 265°F. The sensor is installed
next to the thermostat housing.
The coolant temperature sensor provides an input
voltage to the engine controller (Fig. 3). As coolant
temperature varies the coolant temperature sensors
resistance changes resulting in a different input volt-
age to the engine controller.
When the engine is cold, the engine controller will
demand slightly richer air-fuel mixtures and higher
idle speeds until normal operating temperatures are
reached.
This sensor is also used for cooling fan control.
DISTRIBUTOR PICK-UP—ENGINE CONTROLLER
INPUT
The distributor pick-up provides two inputs to the
engine controller. From one input the engine controller
determines RPM (engine speed). From the other input
it derives crankshaft position. The engine controller
regulates injector synchronization and adjusts ignition
timing and engine speed based on these inputs.
The distributor pick-up contains two signal genera-
tors. The pick-up unit consists of 2 light emitting
diodes (LED), 2 photo diodes, and a separate timing
disk. The timing disk contains two sets of slots. Each
set of slots rotates between a light emitting diode and
a photo diode (Fig. 4). The inner set contains 6
Fig. 3 Coolant Temperature Sensor
14 - 54
FUEL SYSTEM
.
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