Mitsubishi Eclipse. Technical Information Manual (1994) - part 19

1-54

ENGINE 

   Control System

5 volt supply

resistor

Termination

resistor

resistor

Biasing

Both bus circuits are biased (supplied voltage) to

approximately 2.5 volts. The Bus+ and Bus- circuits
are biased through a series circuit (see the illustration
at left). The bus current travels from a 5 volt source
through a 

 ohm resistor to Bus-, then through

a 120 ohm termination resistor to Bus+, and then

to ground through a 13k ohm resistor. Bus bias is
the voltage required to operate the bus.

If the system is functioning normally, the Bus- circuit

voltage is slightly higher than the Bus+ circuit voltage.
This is normal, and is caused by the 120 ohm termina-
tion resistor. The operating bus bias range is approxi-

mately 1.5

 3.5 volts. At voltage above or below

this range, the bus has difficulty communicating cor-

rectly.

Termination

The termination resistors are provided both the inside
of PCM and the inside of TCM.

For the bus circuit to be complete, at least one termina-

tion point must exist.

The resistance in the bus circuit is due to the termina-
tion resistors. It can be measured with an ohmmeter
at the data linkconnector by attaching the two ohmme-
ter leads to the two bus wires. The ohmmeter will

read 100 to 140 ohms for one controller with termina-

tion and 40 to 80 ohms for two controllers with termina-
tion.

The termination points are inside of a controller but
outside the communication chip.

Inputs and Outputs

Messages sent over the communication system can
be considered both inputs and outputs. Output mes-

sages from any one module are used as input mes-
sages to the other modules on the communication
system.

Input messages are used by the modules to imple-
ment specific features. This arrangement allows more

than one module to use information from the same
sensor. Another example of output messages are
those sent to the scan tool for diagnostic purposes.

ENGINE <NON-TURBO>   Control System

1-55

Bus Communication

For communication to occur, the following basics

are needed:

 Bus+ and Bus- wires must be connected in

parallel to all modules.

l

Bus+ and Bus- wires are biased to approxi-
mately 2.5 volts.

l

Bus+ and Bus- wires must have at least one
point of termination.

Communication is based on voltage differential be-
tween the two bus wires. The differential occurs
when two parts of the communication chip, the cur-

rent sink and the current source, are used by the

communication chip to control the bus current flow.

Two different signal conditions can exist when the
bus functions normally; there can be a 

 bit or

a 

 bit.

   OFF   ON

 OFF 

 ON 

2.52

2.52

Bus+   2.49

2.49

 

Voltage

Bus- 

2.51

2.51

I

2.48

2.48

Binary

1

0

1

0

A

F

U

0

0

8

7

 

When the bus circuits are not allowing current to
flow, there is a 

 condition. When the bus is idle

and no messages are being sent, the bus is in the
“1” condition.

When the current source passes a small amount

of current into the Bus+ wire, and the current sink
allows a small amount of current to be passed to
ground, there is a 

 condition.

Messages are made from a series of these “0” and

 signals. Messages are generally transmitted ev-

ery ten or more milliseconds.

Each microprocessor on the bus is connected to

a communication chip. The communication chip
communicates to the CPU the messages transmitted
and received on the bus.

1-56

ENGINE <NON-TURBO>   Engine Electrical

ENGINE ELECTRICAL

GENERATOR

The generator is mounted on the right side of the
engine, and is secured to the cylinder block with
a pivot bracket and an adjustment bracket. The
pivot bracket is secured with three mounting bolts.
The case is grounded to the block, and three electri-
cal connections are provided for charging system
operation.

STARTER MOTOR

The starter motor is located on the left side of the
engine. Locations to connect the battery positive
wires are provided at the starter solenoid.

IGNITION SYSTEM

This engine uses the distributorless electronic igni-
tion system. The distributor-less electronic ignition
system is referred to as the Direct Ignition System.

Basic ignition timing is not adjustable. The 

train control module (PCM) determines spark ad-
vance. The system’s three main components are
the coil pack, crankshaft position sensor, and cam-
shaft position sensor.

The output voltage of the generator is regulated
by the power train control module.

NOTE

The Power supply cable is connected to the genera-
tor with a nut. The PCM voltage control circuit is
the smaller of the two-way connectors at the rear
of the generator.

 

The crankshaft position sensor and camshaft posi-
tion sensor are hall effect devices. The camshaft

position sensor and crankshaft position sensor gen-
erate pulses that are inputs to the PCM. The PCM
determines crankshaft position from these sensors.

The PCM calculates injector sequence and ignition
timing from crankshaft position. For a description
of both sensors; refer to Camshaft Position Sensor
and Crankshaft Position Sensor in this section.

ENGINE <NON-TURBO>   Emission Control System

EMISSION CONTROL SYSTEM

GENERAL INFORMATION

There are three sources of vehicle exhaust emis-

sions generated: the exhaust gases resulting from
combustion, the blow-by gases generated within
the crankcase, and the evaporative emissions gen-
erated from the fuel tank and other components
of the fuel line.
The emissions-control system, which is designed
to control the discharge of these exhaust gases

into the atmosphere, is composed of the following
system components.

(1) Exhaust emission control system
(2) Crankcase emission control system
(3) Evaporative emission control system

Canister

Evaporative emission
purge solenoid

From fuel

Positive
crankcase
ventilation
valve

1

The exhaust emissions-control system reduces the

amount of carbon monoxide, hydro carbon and ox-
ides of nitrogen in the exhaust gases by adding
the exhaust gas recirculation device and the catalytic
converter to fundamental improvements such as
an improvement of the combustion chamber and
the camshaft, as well as other improvements to
the engine such as feedback control of the air/fuel

ratio by the electronically controlled fuel injection

system.
The crankcase emissions-control system is a closed
type so that blow-by gases are not discharged out
to the atmosphere. The evaporative emissions-con-
trol system is the canister type; vapors that are
generated within the fuel tank are introduced into
the intake manifold and are cornbusted so that they
are not emitted out to the atmosphere.

Electric EGR

transducer 

 

 

 

  ,

I

i

,

 only 

-

-

-

-

 secondary

air injection valve

Heated oxygen

 

A F U 0 0 6 3