Mitsubishi Eclipse. Technical Information Manual (1994) — part 18

ENGINE <NON-TURBO> Control System

Operation

The EGR system consists of a vacuum solenoid,
back pressure transducer and a vacuum operated

sure causes the transducer diaphragm to modulate.

valve. When activated, the solenoid allows vacuum

This allows intake manifold vacuum to reach the

to flow to the transducer. Negative exhaust back-

EGR valve. The combination of vacuum on one

pressure allows manifold vacuum from the solenoid

side of the valve diaphragm and exhaust back

to vent to atmosphere. Positive exhaust

sure on the other allows exhaust gases to be
introduced into the intake manifold.

transducer

EGR valve

An EGR system stuck in the closed position prevents
the system from decreasing

emissions. A

tern stuck in the open position can increase

carbon emissions, fuel consumption, and produce

rough engine operation.

ENGINE <NON-TURBO> Control System

The detect operation of the system, the solenoid

is disabled and the

compensation control is

If ttie EGR system is operating properly,

ing’it off shifts the air/fuel ratio in the lean direction.

sensor data should indicate an increase in

gen in the exhaust gases and cause the short term
control to shift rich. The amount of the shift indirectly

monitors the operation of the system.

EGR valve

OFF

term fuel

compensation .

ratio

COMPREHENSIVE COMPONENTS

Refer to Group 13

Troubleshooting in the Service Manual.

ENGINE <NON-TURBO> Control System

DATA TRANSMISSION SYSTEM

The power train control module (PCM) and transaxle
control module (TCM) transfer control data to and

munication line and displays the data on the display.

from each other via a data communication system.

(Various types of data are also received by the scan

The scan tool receives various

of data from

tool from the power train control module through
a line different from this data communication line.)

the transaxle control module through the data

Power train control module

Transaxle control module

Bus+

AFU0084

The power train control module and transaxle control

module communicate with each other by alternately

sending the data in their respective modules to the
data bus.

In other words, the power train control module sends

all its data to the data bus, and the transaxle control

module receives only those data items it needs from

the bus. Then the transaxle control module sends
all its data to the data bus. The power train control

module does not require any specific data from the
data bus.

ENGINE <NON-TURBO> Control System

Bus+ and Bus- Circuits

The data transmission system has two wires

from inducing electromagnetic interference

in parallel to the PCM and TCM. One circuit

into the bus circuits.

is Bus+, and the other is Bus-. For proper
nication, the wires must be twisted together at 1.75”

If the twists are not maintained throughout the bus

intervals. Twisting of the wires is intended to prevent

circuits (at connectors and splices), false signals

switched-to-battery or switched-to-ground circuits

can be conveyed to all modules on the bus.

Communication chip (Communication Control Integrated Circuits)

The bus circuits connect inside all modules to a com-

munication chip. The illustration at left shows a repre-
sentative communication chip block diagram. For
communication to occur, the bus must have Biasing
and Termination (see the following sections.)

’

Transmit data