Chrysler Le Baron, Dodge Dynasty, Plymouth Acclaim. Manual — part 34
PCM SERVICE
(1) Remove air cleaner duct from PCM.
(2) Remove battery.
(3) Remove PCM mounting screws (Fig. 18).
(4) Remove wiring connector from the PCM. Re-
move the PCM.
(5) Reverse the above procedure for installation.
HEATED OXYGEN SENSOR (O
2
SENSOR)
The oxygen sensor is installed in the exhaust man-
ifold (Fig. 19).
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. 20).
Fig. 18 PCM
Fig. 19 Heated Oxygen Sensor
Fig. 20 Oxygen Sensor Electrical Connection
Fig. 16 Canister Purge Solenoid
Fig. 17 Electric EGR Transducer
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FUEL SYSTEMS
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(2) Remove sensor using Tool C-4907 (Fig. 21).
Slightly tightening the sensor can ease removal.
When the sensor is removed, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E
tap. If the same sensor is to be reinstalled, the sensor
threads must be coated with an anti-seize compound
such as Loctite 771-64 or equivalent. New sensors
are packaged with compound on the threads and do
not require additional compound. The sensor must be
tightened to 27 N
Im (20 ft. lbs.) torque.
2.5L FLEXIBLE FUEL MULTI-PORT FUEL INJECTION—SYSTEM OPERATION
INDEX
page
page
Air Conditioning (A/C) Clutch Relay—PCM Output
Air Conditioning Switch Sense—PCM Input
. . . . . 57
Auto Shutdown (ASD) Relay and Fuel Pump
Relay—PCM Output
. . . . . . . . . . . . . . . . . . . . . 61
Battery Voltage—PCM Input
. . . . . . . . . . . . . . . . 58
Brake Switch—PCM Input
. . . . . . . . . . . . . . . . . . 58
Camshaft Position Sensor—PCM Input
. . . . . . . . 58
CCD BUS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Data Link Connector—PCM Output
. . . . . . . . . . . 62
Duty Cycle Evap Purge Solenoid—PCM Output
. 61
Engine Coolant Temperature Sensor—PCM Input . 58
Fuel Injector—PCM Output
. . . . . . . . . . . . . . . . . 62
Fuel Injectors and Fuel Rail Assembly
. . . . . . . . . 65
Fuel Pressure Regulator
. . . . . . . . . . . . . . . . . . . 65
Fuel Supply Circuit
. . . . . . . . . . . . . . . . . . . . . . . 65
General Information
. . . . . . . . . . . . . . . . . . . . . . . 55
Generator Field—PCM Output
. . . . . . . . . . . . . . . 62
Heated Oxygen Sensor (O
2
Sensor)—PCM Input
. 59
Identifying Flexible Fuel Components
. . . . . . . . . . 55
Idle Air Control Motor—PCM Output
. . . . . . . . . . 62
Ignition Coil—PCM Output
. . . . . . . . . . . . . . . . . . 62
Malfunction Indicator (Check Engine) Lamp—PCM
Output
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Manifold Absolute Pressure (MAP) Sensor—PCM
Input
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
Methanol Concentration Sensor—PCM Input
. . . . 59
Modes of Operation
. . . . . . . . . . . . . . . . . . . . . . . 63
Powertrain Control Module
. . . . . . . . . . . . . . . . . 57
Radiator Fan Relay—PCM Output
. . . . . . . . . . . . 63
Speed Control Solenoids—PCM Output
. . . . . . . . 63
Speed Control—PCM Input
. . . . . . . . . . . . . . . . . 60
System Diagnosis
. . . . . . . . . . . . . . . . . . . . . . . . 56
System Operation
. . . . . . . . . . . . . . . . . . . . . . . . 56
Tachometer—PCM Output
. . . . . . . . . . . . . . . . . . 63
Throttle Body
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Throttle Position Sensor (TPS)—PCM Input
. . . . . 60
Torque Converter Clutch Solenoid—PCM Output
. 63
Transaxle Park/Neutral Switch—PCM Input
. . . . . 60
Vehicle Speed Sensor—PCM Input
. . . . . . . . . . . 60
GENERAL INFORMATION
In this model year Chrysler began producing AA-
Body vehicles designed to operate on a mixture of
gasoline and methanol. These automobiles are re-
ferred to as Flexible Fuel vehicles. Fuel system com-
ponents designed for use in flexible fuel vehicles are
referred to as Methanol Compatible.
Flexible fuel vehicles can operate on a mixture of
up to 85 percent methanol, 15 percent unleaded gas-
oline. These vehicles also operate on mixtures con-
taining a lower percentage of methanol or just pure
unleaded gasoline.
IDENTIFYING FLEXIBLE FUEL COMPONENTS
Flexible Fuel vehicles have unique methanol com-
patible fuel system components. Chrysler identifies
methanol compatible components that could be phys-
ically interchanged with gasoline only parts by color-
ing them green or applying a green label or tag to
them. Even though they may appear physically iden-
tical, components for gasoline only AA-body vehicles
must not be used on flexible fuel vehicles.
FLEXIBLE FUEL COMPONENTS
The fuel system of flexible fuel AA-body vehicles
have the following unique methanol compatible com-
ponents.
• Duty Cycle EVAP Purge Solenoid
• Fuel pump module
• Fuel level sensor
• Fuel gauge (gauge cluster).
• Fuel tank
• Fuel pressure regulator (including O-rings)
• Fuel rail
• Fuel injectors (including O-rings)
• Fuel tubes
• Fuel filter
• EVAP canister
• Fuel filler cap
• Fuel filler tube
Fig. 21 Oxygen Sensor Socket
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FUEL SYSTEMS
14 - 55
• Methanol Concentration Sensor
• Pressure relief/Rollover valve
• PCV Valve
• All fuel system and emission system hoses and
tubes
SYSTEM OPERATION
The flexible fuel vehicle’s 2.5L engine use a se-
quential multi-port electronic fuel injection system
(Fig. 1). The powertrain control module (PCM) oper-
ates the electronic fuel injection system. The PCM
provides precise air/fuel ratios and ignition timing
for all driving conditions.
The PCM regulates the air-fuel ratio, ignition coil
dwell and idle speed. The PCM also operates the
high speed and low speed cooling fans, charging sys-
tem, speed control system and various emission con-
trol devices.
Various sensors and switches provide inputs to the
PCM. The PCM converts all inputs into signals and
regulates various systems based on the inputs. The
PCM adjusts the systems it controls to meet chang-
ing operating conditions.
Fuel is injected into the intake port above the in-
take valve in precise metered amounts through elec-
trically operated injectors. The PCM operates the
injectors in a specific sequence. The PCM adjusts the
air/fuel ratio based on the percentage of methanol in
the fuel. The PCM constantly adjusts injector pulse
width to obtain the ideal air fuel ratio for the current
percentage of methanol in the fuel. Injector pulse
width refers to the amount of time an injector oper-
ates.
The PCM adjusts injector pulse width by opening
and closing the ground path to the injectors. Engine
RPM (speed), manifold absolute pressure (air density)
and the percentage of methanol in the fuel are the
primary inputs that determine injector pulse width.
SYSTEM DIAGNOSIS
The powertrain control module (PCM) can test
many of its own input and output circuits. If the
PCM senses a fault in a major system, the PCM
stores a diagnostic trouble code in memory.
Technicians can display stored diagnostic trouble
codes by two different methods. The first is to cycle
the ignition switch On - Off - On - Off - On within 5
seconds. Then count the number of times the mal-
function indicator lamp (check engine lamp) on the
instrument panel flashes on and off. The number of
flashes represents the trouble code. There is a slight
pause between the flashes representing the first and
second digits of the code. Longer pauses separate in-
dividual trouble codes.
Fig. 1 Flexible Fuel MPI Components
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FUEL SYSTEMS
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The second method of reading diagnostic trouble
codes uses the DRBII scan tool. For diagnostic trou-
ble code information, refer to the On-Board Diagnos-
tics section in this group.
CCD BUS
Various modules exchange information through a
communications port called the CCD Bus. The pow-
ertrain control module transmits vehicle load data on
the CCD Bus.
POWERTRAIN CONTROL MODULE
The powertrain control module (PCM) is a digital
computer containing a microprocessor (Fig. 2). The
PCM receives input signals from various switches
and sensors referred to as Powertrain Control Mod-
ule Inputs. Based on these inputs, the PCM adjusts
various engine and vehicle operations through de-
vices referred to as Powertrain Control Module Out-
puts.
PCM Inputs:
• Air Conditioning Controls
• Battery Voltage
• Brake Switch
• Engine Coolant Temperature Sensor
• Camshaft Position Sensor (Distributor Pick-up)
• Manifold Absolute Pressure (MAP) Sensor
• Methanol Concentration Sensor
• Oxygen Sensor
• SCI Receive
• Speed Control System Controls
• Throttle Position Sensor
• Park/Neutral Switch (automatic transaxle)
• Vehicle Speed Sensor
PCM Outputs:
• Air Conditioning Clutch Relay
• Generator Field
• Auto Shutdown (ASD) Relay
• Duty Cycle EVAP Canister Purge Solenoid
• Data Link (Diagnostic) Connector
• Fuel Injectors
• Idle Air Control Motor
• Ignition Coil
• Malfunction Indicator (Check Engine) Lamp
• Radiator Fan Relay
• Speed Control Solenoids
• Tachometer Output
• Torque Converter Clutch Solenoid
Based on inputs it receives, the PCM adjusts fuel
injector pulse width, idle speed, ignition spark ad-
vance, ignition coil dwell and canister purge opera-
tion. The PCM regulates operation of the radiator
fan, A/C and speed control systems. Also, the PCM
changes generator charge rate by adjusting the gen-
erator field.
The PCM adjusts injector pulse width (air-fuel ra-
tio) based on the following inputs.
• Battery voltage
• Coolant temperature
• Exhaust gas content
• Engine speed
• Manifold absolute pressure
• Methanol percentage of fuel
• Throttle position
The PCM adjusts ignition timing based on the fol-
lowing inputs.
• Coolant temperature
• Engine speed
• Manifold absolute pressure
• Methanol percentage of fuel
• Throttle position
The auto shutdown (ASD) and fuel pump relays are
mounted externally. The PCM turns both relays on
and off through the same circuit.
The camshaft position sensor (distributor pick-up)
sends a signal to the PCM. If the PCM does not re-
ceive a camshaft position sensor signal within ap-
proximately
one
second
of
engine
cranking,
it
deactivates the ASD and fuel pump relays. When
these relays deactivate, they shut off power to the
fuel injectors, fuel pump, ignition coil, methanol con-
centration sensor and oxygen sensor heater element.
The
PCM
contains
a
voltage
converter
that
changes battery voltage to a regulated 8.0 volts to
power the distributor pick-up methanol concentration
sensor and vehicle speed sensor. The PCM also pro-
vides a 5.0 volts supply for the engine coolant tem-
perature sensor, manifold absolute pressure sensor
and throttle position sensor.
AIR CONDITIONING SWITCH SENSE—PCM INPUT
When the operator puts the A/C or defrost switch
in the ON position and the low pressure and high
pressure switches close, the PCM receives an input.
The input indicates the operator selected air condi-
tioning. After receiving this input, the PCM acti-
vates the A/C compressor clutch by grounding the
Fig. 2 Powertrain Control Module
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FUEL SYSTEMS
14 - 57
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