1990 MITSUBISHI ECLIPSE light

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14-28FUEL SYSTEM- Ennine Control Unit
The engine control unit has an
onboard diagnosis
function, which is used mainly to diagnose the
sensors, thus facilitating system checks and troub-leshooting. It also has a fail-safe/backup function tc
ensure passenger and vehicle safety.
Onboard self-
diagnosisMainly for detecting failure of sensors
and foroutputting diagnosis code.
for detecting failure of sensors, etc. related
toemission control and to turn ON warning light
(Malfunction indicator light).
> Codes can be read by voltmeter.
ENGINE CHECK light is turned
2 ON.
The engine control unit is mounted in the passenger compart-
ment, at the location indicated in the illustration.,

FUEL SYSTEM- Engine Control Unit14-29
SFUllSOTerminal
ConnectionTerminalConnectionNo.
No.
1Self-diagnosis output53EGR control solenoid valve (California only)
2Diagnosis/data transfer select terminal54Power transrstor for No. 1 and No. 4 cylinder
‘3Turbo meter
55Power transistor for No. 2 and No. 3 cylinder
4Oxygen sensor56Control relay (Fuel pump control)
5Power steering oil pressure switchl 57Fuel-pressure control valve
6Idle position switch58Coil “Al ” for idle speed control servo
7Air conditioner switch59Coil “A2” for idle speed control servo
8Intake air temperature sensor60No. 3 injector
l 9Detonation sensor61No. 4 injector
10Air flow sensor62Purge control solenoid valve11
-63Control relay
12Ignition timing adjustment connector64Engine warning irght (Malfunction indicator light)
13Control relay (Fuel pump drive signal)65Air conditioner relay
l 14Air flow sensor active filter reset66Control relay
15EGR temperature sensor (California only)67Coil “Bl ” for idle speed control servo
16Barometric pressure sensor68Coil “B2” for idle speed control servo
17Sensors ground101Ground
18Vehicle speed sensor102Power supply
19Throttle position sensor103Power supply for backup
20Coolant temperature sensor
104Inhibitor switch
21Crank angle sensor‘105
Waste gate solenoid valve
22Top dead center sensor106Ground
23Power supply for sensors (5 volts)107Power supply
24Sensors ground108“ST” terminal for ignition switch
51No. 1 injector109Ignition pulse detect
52No. 2 injector170“IG ” terminal for ignition switch
NOTETerminals indicated by the l symbol are applicable only to turbo models.

14-30SELF-DIAGNOSISFUEL SYSTEM- Engine Control Unit
There are 16 diagnosis items, as listed below; the
diagnosis results are stored in computer memory.The diagnosis memory is maintained by backup
The stored results can be ready by connecting apower from the battery (not by way of the ignition
circuit tester or voltmeter to the diagnosis
connec-switch) so that it will not be lost even if the ignition
switch is turned OFF.
tor.
DiagnosisOutput pattern
codeEl
None
lP
@ 11l-l
@ 12n@ 13
@ 14
@ 21Ul n
Diagnosis items
Faulty computer in the engine control unitMalfunction of the air/fuel ratio control system
Open or short circuit in the oxygen sensor circuit
Open or short circuit in the air flow sensor circuit
Open or short circuit in the intake air temperature sensor
circuit
Open or short circuit in the throttle position sensor circuit
Open or short circuit in the engine coolant temperature sensor
circuit
022u1 nn
No voltage change of the crank angle sensor signal
,
@
23
u u-inn
No voltage change of the TDC sensor signal
24uu-uvinnnnNo voltage change of the vehicle speed sensor signal
Q25uuuuuunnnnnOpen or short circuit in the barometric pressure sensor
2 31I-~-~---~ nOpen circuit in the detonation sensor circuit
@ 41uuul nOpen circuit in the injection circuit
042UUuLJul
Malfunction of the control relayOpen or short circuit in the fuel pump drive circuit
z 43UUULnlulMalfunction of the
EGR system
Open or short circuit in the EGR temperature sensor circuit
%4u u u uvinnOpen circuit in either of ignition coil circuit
0nNormal (with none of above faults)
. IA-r-NUltl 1: l 2: for California@ denotes items indicated by an illuminated engine warning light

FUEL SYSTEM - Engine Control Unit14-31
r
L
IMPI
Ground
1 Engine control unit
Engine wam-
$b?Stionindicator
light)The diagnosis connector is located next to the junction block.
By connecting a voltmeter between the
No.1 and No.12terminals of the diagnosis connector, the meter pointer will
deflect according to the output pattern shown before so that
the diagnosis code can be read.
To clear the diagnosis codes that are stored in the memory,
disconnect the
.battery ground cable for 10 seconds.
When a malfunction is detected in items related to emission
control (items marked
Q in the table), the engine warning light
(Malfunction indicator light) is illuminated to warn the driver of
the necessity for an engine check.
When the malfunction is corrected, the light goes off. The light
also goes off when the ignition switch is turned OFF. At that
time, it will not come on when the ignition switch is turned ON
unless a malfunction is detected again.
However, the light remains on for
E.5 seconds, after the
ignition switch is turned on. This is to allow the driver to check
that the engine warning light circuit is operating normally.

__.-~-..- -
FUEL SYSTEM- Ermine Control Unit
FAIL-SAFE AND BACKUP FUNCTiON
(1) The fail-safe function controls the system so
that passenger and vehicle safety can be
maxi-
mized. in the event of failure of sens.ors or other
parts.If a sensor related to
ISC fails, for example, the
engine control unit is programmed to prevent
sharp increases in the engine speed.(2) The backup function of the engine control unit
ignores the output signal of a failed sensor and
instead uses a built-in program or set of values
so that the vehicle may continue to function. The
operating state when the backup function is
being used, is termed the emergency mode, and
the engine, control unit keeps the engine warn-
ing light ON during this mode.
Fail-safe/Backup Function
Control contentsFaulty system
Fuel injection control
Idle speed controlIgnition timing control
Air flow sensor
Uses throttle position sensorFixes stepper motor atUses throttle position sensorsignal for control.
position wider than idle.signal for control.
Intake air
temper-Provides control with intake
Provides control with intakeProvides control with intake
ature sensorair temperature assumed to
be 25°C (77°F).air temperature assumed toair temperature assumed tobe 25°C (77°F).be 25°C (77°F).Throttle position
-Does not perform driving and-sensor
acceleration/deceleration
control.
Engine coolantProvides control with engine
Provides control with engineProvides control with engine
temperaturecoolant temperature
coolant temperaturecoolant temperature
sensorassumed to be 80°C (176°F)assumed to be 80°C (176°F).assumed to be 80°C (176°F).BarometricProvides control with
baro-Provides control with baro-Provides control with baro-pressure sensormetric pressure assumed to
be 760
mmHg (30 in.HgI.metric pressure assumed tometric pressure assumed tobe 760 mmHg (30 in.Hg).be 760 mmHg (30 in.Hg).Detonation sensor
-Retarded about 3 degree.Ignition coil
Fuel not injection to a cylinder-whose ignition signal is
abnormal.
TDC sensorOxygen sensor
No fuel injection.-
Feedback control of air/fuel-
ratio by oxygen sensor signal
is not made.

FUEL SYSTEM -Auto-cruise Control System14-59AUTO-CRUISE CONTROL SYSTEMRIIPA&A
using the auto-cruise control system, the vehicle
oar-rbe maintained at a constant driving speed
[between 40 km/h (25 mph) or higher and 145 km
(90 mph) or lower], as selected by the driver,
without using the accelerator pedal.The actuator is the DC motor-driven type for a high
degree of adherence to the set speed. A flexiblesupport system is used for installation of the
actuator in order to prevent the transaxle of body
vibrations to the actuator.
CONSTRUCTION DIAGRAM
control switchOJAO2SS
Accelerator
Actuator
ab’ea\ A
Inhibitor switch Vehicle speed sensor
(reed switch)
Accelerator cab1e.A/IClutch switch
/Accelerator pedal switch IStop light switch

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14-60FUEL SYSTEM - Auto-cruise Control System
SYSTEM BLOCK DIAGRAM
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f?,: 0,
,’
vi
switch cpJT>
Auto-cruise control switch. MAIN switchl SET (COAST) switchl RESUME (ACCEL) switc
I
Intermedi-ate linkActuator
mechanismCOMPONENT PARTS AND FUNCTION OUTLINE
Component part
Vehicle speed sensor
6\uto-cruise control unit
Function
Converts vehicle speed to pulse,
Receives signals from sensor and control switches; microcomputercontrols all auto-cruise control functions
ActuatorRegulates the throttle valve to the set opening by signals from the
auto-cruise control unit
Control switchMAIN switch
Switch for auto-cruise control power supply
SET
(COAST) switchControls auto-cruise control functions by SET (COAST) and
1 RESUME (ACCELIRESUME (ACCEL) switch
Cancel switch
Stop light switchClutch switch
Outputs the auto-cruise control cancel signals
Inhibitor switch CA/T>
Accelerator switch
During constant speed driving, the accelerator pedal is inactive and
the accelerator switch is turned ON.
Therefore, OFF signal is output from the auto-cruise control unitto the ELC
4A/T control unit during constant speed driving only.
4-I-Ed automatic transaxle control unitControls overdrive ON and OFF based on overdrive ON andOFF signals from the auto-cruise control unit for the auto-cruise
controlAuto-cruise indicator lightThis indicator light illuminates to indicate that the vehicle is
traveling in the auto-cruise mode.
Diagnosis connectorBY connecting a voltmeter control unit diagnosis and input-check
codes can be read out (for details, refer to P. 14-69).

14-64FUEL SYSTEM - Auto-cruise Control System
FixedAccelera-FixedSpeed -c tion-LC speed
High
Vehic’e iapprox. 40 km/hspeedG!5 mph) or hagher]Low
’When the RESUME
(ACCEL) Switch is Kept Turned
While the RESUME switch is ON, the actuator’s DC
mote,caused to rotate to the PULL side; the vehicle speed when the
switch is switched OFF as acceleration continues is entered in
the memory, and is thereafter controlled as the fixed speed.
CANCELLATION
When, during fixed-speed driving, the signals described below
are input, conductivity to the electromagnetic clutch is inter-
rupted, thus
cancelling the auto-cruise control system.
l Stop light switch ON (brake pedal depressed)
l Clutch switch ON (clutch pedal depressed)
lInhibitor switch ON (selector lever at
“P” or “N” position)
LOW-SPEED LIMIT
There is automatic cancellation at or below the low-speed limit
vehicle speed [approximately 40 km/h (25 mph)].
HIGH-SPEED LIMIT
The vehicle cannot be driven at a fixed speed which is at or
higher than the high-speed limit [approximately 145 km/h
(90
mph)l.Note that the vehicle speed memorized when the SET switch
a5pressed while the vehicle is traveling at the high-speed limit or
higher
vvill be the high-speed limit vehicle speed.
FAIL-SAFE FUNCTION
When the following situations are encountered during fixed-
speed driving, the signals to interrupt, conductivity to the
electromagnetic clutch are input, thus canceling the auto-cruise
control system.
0
0
0When vehicle speed decreases to the low-speed limit
[approx. 40 km/h (25 mph)].
If the vehicle speed decreases to a speed which is
approximately 20 km/h (12 mph) or more below ‘the
memorized vehicle speed.
When the vehicle speed drops by 20 km/h
(12 mph) or more
after having reached the set speed -10 km/h (-6 mph) in
the RESUME mode.
If there is damaged or disconnected wiring of the input line
(stop light switch load side) of the stop light switch.
if there is no input of the vehicle speed signal for a certain
fixed time (1 second or longer).
If the SET and RESUME control switches are switched ON
at the same time.
If the cancel switches (stop light switch, clutch switch or
inhibitor switch) and command switches (SET switch
orRESUME switch) are switched ON at the same time.
if the actuator clutch driver (transistor) of the control unk
remains ON (short-circuit).