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.
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