Mitsubishi Eclipse. Technical Information Manual (1994) - part 11

ENGINE <NON-TURBO>   Control System

-Upstream

The input from the upstream heated oxygen sensor
tells the PCM the oxygen content of the exhaust
gas. Based on this input, the PCM fine tunes the
air-fuel ratio by adjusting injector pulse width.

The sensor produces from 0 to 1 volt, depending
upon the oxygen content of the exhaust gas in the
exhaust manifold. When a large amount of oxygen
is present (caused by a lean air-fuel mixture), the
sensor produces voltage as low as 0.1 volt. When
there is a lesser amount of oxygen present (rich
air-fuel mixture) the sensor produces a voltage as
high as 1.0 volt. By monitoring the oxygen content
and converting it to electrical voltage, the sensor
acts as a rich-lean switch.

The heating element in the sensor maintains correct
oxygen sensor temperature. Maintaining correct

sensor temperature at all times allows the system
to enter into Closed Loop operation sooner. Also,
it allows the system to remain in Closed Loop opera-

tion during periods extended’ idle.

In Closed Loop operation the PCM monitors the
inputs from the heated oxygen sensors (along with

other inputs). In Closed Loop, the PCM adjusts injec-
tor pulse width based on the upstream heated oxy-
gen sensor input. During Open Loop operation the
PCM ignores the inputs from both the upstream
and downstream heated oxygen sensors. In Open
Loop, the PCM adjusts injector pulse width based
on preprogrammed (fixed) values and inputs from
other sensors.

The upstream oxygen sensor threads into the outlet
flange of the exhaust manifold.

Downstream

The downstream heated oxygen sensor threads

into the exhaust pipe at the rear of the catalytic
convertor. The downstream heated oxygen sensor
input is used to detect catalytic convertor 

tion. As the convertor deteriorates, the input from

the downstream sensor begins to match the 
stream sensor input except for a slight time delay.

By comparing the downstream heated oxygen 

sor input to the input from the upstream sensor,
the PCM calculates catalytic convertor efficiency.

 Downstream heated

 oxygen sensor

convertor

ENGINE <NON-TURBO>   Control System

VEHICLE SPEED SENSOR

Vehicles with manual transaxle use a vehicle speed

deceleration conditions, the PCM adjusts the idle

sensor. The sensor is located in the transaxle 

air control motor to maintain a desired MAP value.

sion housing. The power-train control module (PCM)

Under idle conditions, the PCM adjusts the idle air

determines vehicle speed from the sensor input.

control motor maintain a desired engine speed.

The vehicle speed sensor generates 8 pulses per

On vehicles with automatic transaxles, the PCM

sensor revolution. These signals are interpreted

receives the vehicle speed input from the transaxle

along with a closed throttle signal from the throttle

control module (TCM). The TCM calculates vehicle

position sensor by the PCM. The inputs are used

speed from its output speed sensor and turbine

to determine if a closed throttle deceleration or a

speed sensor.

normal idle (vehicle stopped) condition exists. Under

 

 

 bracket 

Vehicle
speed

sensor

AIR CONDITIONING SWITCH

When air conditioning or defrost is selected the PCM

receives an input signal that allows it to ground

the A/C clutch relay. This provides power to the

A/C clutch. In addition, the PCM adjusts the idle
air controller motor to compensate for the increased
engine load and maintain target idle.

ENGINE <NON-TURBO>   Control System

POWER STEERING PRESSURE SWITCH

A pressure switch is located on the power steering

unit’s body to signal periods of high pump load and
pressure, such as those which occur during parking
maneuvers. This allows the PCM to maintain target

PARK/NEUTRAL SWITCH

The park/neutral switch is located on the automatic
transxale housing. Manual transaxles do not use
park neutral switches. The switch provides an input
to the PCM. The input indicates whether the auto-
matic transaxle is in Park, Neutral, or a drive gear

idle speed. To compensate for the additional engine
load, the PCM increases airflow by adjusting the 
idle air control motor.

selection. This input is used to determine idle speed
(varying with gear selection), fuel injector pulse
width, and ignition timing advance. The park neutral
switch is sometimes referred to as the neutral safety
switch.

       

 

IGNITION SWITCH-IG (J2 SENSE)

The ignition sense input informs the power-train con-
trol module (PCM) that the ignition switch is in the

Crank or Run position.

ENGINE <NON-TURBO>   Control System

KNOCK SENSOR

The knock sensor threads into the side of the cylinder

Knock sensors contain a piezoelectric material

block below the intake manifold. When the knock

which constantly detects engine knock vibration and

sensor detects a knock in one of the cylinders, it

sends an input voltage (signal) to the PCM while

sends an input signal to the PCM. In response,

the engine operates. As the intensity of the engine

the PCM retards ignition timing for all cylinders by

knock increases, the knock sensor output voltage

a scheduled amount.

also increases.

Knock

BRAKE SWITCH

When the brake switch is activated, the power-train
control module (PCM) receives an input indicating
that the brakes are being applied. After receiving
this input the PCM maintains idle speed to scheduled

RPM through control of the idle air control motor.

The brake switch is mounted on the brake pedal
support bracket.

BATTERY VOLTAGE
The power-train control module (PCM) monitors the
battery voltage input to determine fuel injector pulse
width and generator field control. If battery voltage

is low the PCM will increase injector pulse width
(period of time that the injector is energized).