Mitsubishi Eclipse. Technical Information Manual (1994) - part 10

ENGINE 

   Control System

The throttle position sensor (TPS) connects to the
throttle blade shaft. The TPS is a variable resistor
that provides the powertrain control module (PCM)
with an input signal (voltage). The signal represents
throttle blade position. As the position of the throttle
blade changes, the resistance of the TPS changes.

The PCM supplies approximately 5 volts to the TPS.
The TPS output voltage (input signal to the 
train control module) represents throttle blade 

CAMSHAFT POSITION SENSOR

The PCM determines ignition and fuel injection syn-
chronization and cylinder identification from inputs

provided by the camshaft position sensor and 

tion. The TPS output voltage to the PCM varies
from approximately 0.40 volt at minimum throttle
opening (idle) to a maximum of 3.80 volts at wide
open throttle.

Along with inputs from other sensors, the PCM uses
the TPS input to determine current engine operating
conditions. The PCM also adjusts fuel injector pulse
width and ignition timing based on these inputs.

shaft position sensor. From the two inputs, the PCM
determines crankshaft position and cylinder cycle.

 Camshaft

 

 

 

ENGINE <NON-TURBO>   Control System

1-19

The camshaft position sensor attaches to the rear
of the cylinder head. A target magnet attaches to
the rear of the camshaft and indexes to the correct
position. The target magnet has four different poles
arranged in an asymmetrical pattern. As the target

magnet rotates, the camshaft position sensor
senses the change in polarity. The sensor output

switch switches from high (5.0 volts) to low (0.30
volts) as the target magnet rotates. When the north
pole of the target magnet passes under the sensor,
the output switches high. The sensor output switches

low when the south pole of the target magnet passes
underneath.

 Rear of

 

The camshaft position sensor is mounted to the

rear of the cylinder head. The sensor also acts as

CRANKSHAFT POSITION SENSOR

The PCM determines what ignition coil to energize
from the crankshaft position sensor input and the
camshaft position sensor input. The second crank-
shaft counterweight has machined into it two sets

Target

magnet

AF 

a thrust plate to control camshaft 

of four timing reference notches and a 60 degree
signature notch. From the crankshaft position sensor
input the PCM determines engine speed and crank-
shaft angle (position).

Crankshaft 
position
sensor

AFU0071

ENGINE <NON-TURBO>   Control System

The notches generate pulses from high to low in
the crankshaft position sensor output voltage. When
a metal portion of the counterweight aligns with
the crankshaft position sensor, the sensor output
voltage goes low (less than 0.3 volts). When a notch
aligns with the sensor, voltage spikes high (5.0 volts).
As a group of notches pass under the sensor, the
output voltage switches from low (metal) to high

(notch) then back to low.

If available, an oscilloscope can display the square

wave patterns of each voltage pulse. From the width
of the output voltage pulses, the PCM calculates
engine speed. The width of the pulses represent
the amount of time the output voltage stays high

before switching back to low. The period of time

the sensor output voltage stays high before switch-

ing back to low is referred to as pulse width. The

faster the engine is operating, the smaller the pulse
width on the oscilloscope.

lates crankshaft angle (position). In each group of

timing reference notches, the first notch represents
69 degrees before top dead center (BTDC). The
second notch represents 49 degrees BTDC. The
third notch represents 29 degrees. The last notch

in each set represents 9 degrees before top dead

center (TDC).

The timing reference notches are machined to a
uniform width representing 13.6 degrees of crank-
shaft rotation. From the voltage pulse width the PCM
tells the difference between the timing reference

notches and the 60 degree signature notch. The

60 degree signature notch produces a longer pulse
width than the smaller timing reference notches.

If the camshaft position sensor input switches from
high to low when the 60 degree signature notch

passes under the crankshaft position sensor, the
PCM knows cylinder number one is the next cylinder
at TDC.

By counting the pulses and referencing the pulse

from the 60 degree signature notch, the PMC 

2 1 0 ”

150”

  2 1 0 ”

I

T D C

TDC

TDC

TDC

69” 

3

Crank
signal

I

Crank
angle 

0 4 0 8 0 1 2 0 1 6 0 2 0 0 2 4 0 2 8 0   3 2 0 0 4 0 8 0 1 2 0 1 6 0 2 0 0 2 4 0 2 8 0 3 2 0 0

AFU0072

ENGINE <NON-TURBO>  - Control System

I-21

The crankshaft position sensor mounts to the engine block behind the generator, just above the oil filter.

AFU0073

HEATED OXYGEN SENSORS

As vehicles accumulate mileage, the catalytic con-
vertor deteriorates. The deterioration results in a

less efficient catalyst. To monitor catalytic convertor
deterioration, the fuel injection system uses two
heated oxygen sensors. One sensor upstream of

the catalytic convertor, one downstream of the con-
vertor. The powertrain control module (PCM)
compares the reading from the sensors to calculate
the catalytic convertor oxygen storage capacity and
efficiency. Also, the PCM uses the upstream heated
oxygen sensor input when adjusting injector pulse
width.

When a deteriorating catalyst’s efficiency drops be-

low emission standards, the PCM stores a diagnostic

trouble code and illuminates the malfunction indica-
tor lamp (MIL).

The MFI relay (automatic shut down relay) supplies
battery voltage to both the upstream and down-
stream heated oxygen sensors. The oxygen sensors
are equipped with a heating element. The heating
element keeps the sensors at proper operating tem-
perature during all operating modes.