1991 MITSUBISHI ECLIPSE Service Manual

AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
3. CHECKING THE RESUME SWITCH CIRCUIT.
” ,, . .
Auto-cruisecontrol unit
Cruise-controlswitchDescription of operation
The set speed (before cancellation) resumes when the RE-SUME switch is switched ON, even if the constant-speed
control has been cancelled.That speed will not resume, however, even if the RESUME
switch is switched ON, if the CRUISE switch is switched OFF
and if the vehicle speed decreases to 40 km/h’
(25 mph) or
lower.
In addition, when the RESUME is switched ON and held while
the vehicle is traveling at a constant speed, the vehicle speed
will increase; the speed at which the switch is subsequently
released will become the newly set constant speed.Current flows to the control
unit, the cruise control switch
(RESUME), and to ground.
Troubleshopting hint
Diagnosis-No. 15
(automatica& canceelied)ECU terminal voltage
Tez3!alSignalConditionsTerminalvoltage
18RESUMEWhen the RESUMEOVswitchswitch is,switchedON.
When the RESUME
“o”;:“h IS swrtched;;;;g;
\ ‘)
13AO365,,4. CHECKING THE VEHICLE-SPEED SENSOR CIRCUIT
Auto-cruisecontrol unit
Combination
meter
Junction
block
13A0366Description of operation
The vehicle-speed sensor is installed within the sljeedometer; it
sends to the control unit pulse signals that are proportional to
the rotation speed (i.e., the vehicle speed) of the transaxle’soutput gear.
This vehicle-speed sensor is the reed switch type of sensor; it
generates four pulse signals for each rotation of the speedo-
meter’s driven gear.Troubleshooting hint
Diagnosis-No. 12 (automatically
cancelled)ECU terminal voltage
Move the vehicle
forward slowly.

14-116AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
5. CHECKING THE AUTO-CRUISE CONTROL VACUUM PUMP
Ignitionswitch (IG,)I
SET
ON
Cruise-controlswitchDescription of operation
Hold modeWhen the SET switch is turned ON by the driver turning the
CRUISE switch ON when a determined speed is reached, thecontrol unit receives a set signal, and turns the auto-cruise
vacuum pump motor ON. After the constant speed is reached,
the motor, control valve and release valve are repeatedly turned
ON and OFF according to driving conditions.
Acceleration mode
When the RESUME switch is pressed, the control unit receives
a RESUME signal and it not only turns the auto-cruise vacuum
pump motor ON but also turns the control valve and releasevalve ON (valve is closed).
Deceleration mode
When the SET switch is held down, the control unit receives a
set signal and
it not only turns the auto-cruise vacuum pumpmotor and control valve OFF (valve is opened) but also turns the
release valve ON (valve is closed).
Release modeWhen the CRUISE switch is turned OFF, the control unit
receives a cancel signal and it not only turns the auto-cruisevacuum pump motor OFF but also turns the control valve and
release valve OFF (valve is opened).Troubleshooting hint
Diagnosis-No. 11 (automatically
cancelled)ECU terminal voltage

i-._AUTO-CRUISE CONTROL SYSTEM
- Troubltyshootf$6. CHECKING THE STOP LIGHT SWITCH CIRCUIT
Sub fusible link @
vacuum
w-vStop light
Auto-cruisecontrol unit13A0366Description of operation
When the brake pedal is depressed during constant-speedtravel, the stop light switch’s (NC) contacts for the cruise-control system open, with the result that the current to the
auto-cruise vacuum pump is interrupted, thus canceling the
constant-speed travel.
At the same time, moreover, the closing of the (NO) contacts
for the stop light results in the sending of the cancel signal to
the control unit, so that the auto-cruise vacuum pump current is
discontinued within the control unit, thereby canceling the
constant-speed travel.
The flow of current is from the sub fusible link
@I to fuse No. @
of the junction block, the stop light switch, and the control unit.Troubleshooting hint
ECU terminal voltage
TerminalSignal
No.
15
t-i-
Stop light
switch (load
side)pedal is depressed.
NOTENC: Indicates ON at all times. (For cruise contra!)NO: Indicates OFF at all times. (For stop light)l,_7. CHECKING THE INHIBITOR SWITCH CIRCUIT
Auto-
cruise
controlunit
Vehicles with x
theft-alarmIVehicles without5 theft-alarm systemsystem br
*Theft-’ nI Ialarm, ._I
starterz
relayQlOF: N A_ 3
Inhibitor
switchDescription of operation
The inhibitor switch also functions as the switch for the starter.If the selector lever is moved to the “N” position during
constant-speed travel, current flows to the control unit, inhibitorswitch, theft-alarm starter relay (vehicles with theft-alarm
system), starter motor, and to ground; the cancel signal istherefore input to the control unit, thus canceling the constant-speed travel.5Troubleshooting hint
ECU terminal voltage
TeE!alSignalConditionsTerminalvoltage
1Inhibitor switchAt all timesSystemvoltage
C.starter
motor13A036BNOTERefer to GROUP 8-Theft-alarm System forthe + (asterisk) on“Theft-alarm System”.

14-118AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
8. CHECKING THE CLUTCH SWITCH CIRCUIT
Auto-cruisecontrolunit9
2ClutchswitchOFF ON
1m11Junction
blockI
13AO370Description of operation
If the clutch pedal is pressed wht driving at a constant speed,
the clutch switch is turned ON and a cancel signal is input to the
control unit and the determined driving speed is canceled
because current flows to the clutch, switch junction block from
the control unit and to ground.Troubleshooting hint
ECU terminal voltage
TerminalSignal
No.
1Clutch switch
t--l--II
ConditionsTerminalvoltage
When the clutch
pedal is depressed.
When the clutchpedal is not de-
pressed.
9. CHECKING THE CIRCUITS RELATED TO THE ACCELERATOR SWITCH OFF FUNCTION
Ignition switchm
& Accel-/Description of operation
The accelerator switch is a switch that detects the operationalstatus of the accelerator pedal; it is one of the sensors of theautomatic, transaxle.Because the status of the accelerator pedal during constant-speed driving is non-operational, the ground circuit (transistorTr2) of the accelerator switch is switched OFF only during
constant-speed driving in order not to interfere wtth the function
of the automatic transaxle.Troubleshooting hint
ECU terminal voltage
TerminalNo.SignalConditionsTerminalvoltaoe
’ 3Control unitAt all times
power supply
9Accelerator
When the accel-ovswitcherator pedal is
depressed.
When the accel-Systemerator pedal is not
depressed.voltage
\lOTEJC: Indicates ON at all time.
13AO3711 Not in operation ) OFF 1 ON (

AUTO-CRUISE CONTROL SYSTEM - Troubleshooting1~~ppGJ”10. CHECKING THE CIRCUITS RELATED TO THE OVERDRIVE-CANCELLATION FUNCTION

block
Ov&rive
Auto-cruisecontrol unitswitch
(16)
A574Al-r
control
unitm
(18)Description of operation
This is a function that cancels the overdrive
fur&on for a
certain fixed period of time, if .during constant-speed travel inoverdrive, the actual vehicle speed decreases to less than the
vehicle speed retained in the memory, and then after a short
time causes the vehicle speed to return to the vehicle speed
retained in the memory.
Overdrive is
cancelled under the following conditions.If, during constant-speed travel, the actual vehicle speed
decreases to 7 km/h (4.4 mph) or more below the set vehicle
speed.
Under either of the conditions described above, the overdrive-
ON signals output from the microcomputer (with the control
unit) are no longer output, and transistor Tr, is switched OFF.
As a result, transistor Tr2 is also switched OFF, causing the
current passing through the overdrive switch of the selector
handle to be interrupted at transistor Tr2, with the result that the
drive is controlled ‘at 3rd gear.Troubleshooting hint
ECU terminal voltage
rerNmdra’SignalConditionsTerminali voltage
104A/T control,
unitWhen the overdrive‘sw$ch IS swrtched$ta;;
11;;tt;iveWhen the overdrives&itch IS switched%‘Gg;

14-120AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
11. CHECKING THE THROTTLE POSITION SENSOR AND IDLE SWITCH CIRCUIT<1.8L Engine>
Throttle
position
sensor
MPI controlunitnw374<2.0L DOHC Engine>
ruiseI unitDescription of operation
“s
The throttle position sensor and idle switch are mounted in the,
motor position sensor or throttle body and are sensors in theMPI system. The idle switch is turned OFF when the accelera-
tor pedal is pressed and ON when it is released. In addition,
throttle position sensor output voltage varies according to thedegree of opening of the throttle valve.Troubleshooting hint

Diagnosis-No. 17

Diagnosis-No. 17
ECU terminal voltageTeKlna’
SignalConditionsTerminal
voltage
4Idle switchWhen accelerator
pedal is pressedXFgr
When acceleratorovpedal is released
5ThrottleWhen accelerator 4.OV-5.5V
position sensorpedal is pressedall the way down
When accelerator 0.48-0.72Vpedal is released

AUTO-CRUISE CONTROL SYSTEM - Troubleshooting'14421
16A065i
Auto-cruise
16LOOS
SELF-DIAGNOSIS CHECKSelf-diagnosis checking is performed when there has been an
automatic cancellation, without cancel switch
operati’on.(1) The following method can be used for checking the
diagnosis. Note that the diagnosis check connector is
located under the driver’s side instrument panel.
Connect a voltmeter between the ground terminal and the
terminal for auto-cruise control of the diagnosis check
connector.It is possible to discover which circuit is the cause of the
cancellation by verifying the indication shown by the
voltmeter with the display patterns shown on the next
page.(2) When the diagnosis code No. is displayed, inspect accord-
ing to the inspection chart No. related to each code No.
NOTECanceling the diagnosis codes
The diagnosis codes remain in memory until the battery is
turned off but they can be canceled in the following ways
without disconnecting the battery terminals.
1. By turning on the ignition switch
2.By turning the cruise switch ON while the SET switch is ONand then, within 1 second, turning the RESUME switch
ON. (Put into condition for input check reception)
3.By turning ON set SET switch and stop light switch at the
same time and continuing the ON condition for 5 seconds
or more.
4.By checking that the diagnosis codes are canceled using avoltmeter.

14-122AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
DIAGNOSIS DISPLAY PAlTERNS AND CODES
CodeNo.
11
Display patterns (output codes)(Use with voltmeter)
“,;1 fl 1 j--
Probable cause
Abnormal condition of auto-cruise
vacuum pump drive system
Check chart No.
No. 5
12Abnormal condition of vehicle-speed sig-No.4nal system
15"16"12vControl switch malfunction (when SETNo.2, 3
and RESUME switches switched ONovsimultaneously for more than 25 seconds)
I ‘,“,-I r
Abnormal condition of auto-cruiseNo.6,7,8control unit
17Abnormal condition of throttle positionNo. 11
sensorAbnormal condition of idle switch,3*0356
NOTE
1. Codes indicated by the* symbol are displayed, if the conditions are satisfied, even if the system is
normal. In either case, the system is normal if it can be reset. If there is an automatic cancellation not
intentionally made by the driver, however, excluding cancellations explicitly made by the cancel
procedure, there may be a temporary malfunction such as poor contact of a harness connector even
though the system can be reset, and for that reason it is necessary to check according to each
individual check chart that is applicable.Display
when vehicle speed isapproximately 20 km/h (12 mph) less thanor before the auto-cruise control systemis set
ON (12V)
OFF (OV)2. Diagnosis codes are displayed when, after cancellation of
the auto-cruise control system, the vehicle speed
de-creases to less than approximately 20 km/h (12 mph), and
are canceled by turning OFF the battery or canceling the
diagnosis codes. (Refer to
P.14-121.)After the diagnosis codes in the memory are erased, if
(when the power supply of the electroinc control unit is
switched ON once again) the power supply of the
electronic control unit is normal, the diagnosis output
code display will be as below, regardless of whether the
system condition is normal or not.
Continuous ON/OFF signals will be displayed at 0.5-second
intervals.(Refer to the figure at the left.)