MITSUBISHI GALANT 1989 Service Repair Manual

AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
13-34
9
8. CHECKING THE CIRCUITS RELATED TO THE OVERDRIVE-CANCELLATION
FUNCTlON

Ignitionswitch
4 A/T
control
module
IO
-I-m
7
E-lWA001
Description of operation
This is a function that cancels the overdrive
function for a certain fixed period of time, if during constant-speed travel in overdrive, the actual vehi-
cle 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 canceled under the following condi-
tions. 1. If the “RESUME” switch is used.
2. If, during constant-speed travel, the actual vehicle speed decreases to 1.25
km/h (.78
mph) or more below the set vehicle speed. Under either of the conditions described above,
the overdrive-ON signals output from the micro- computer (within the control unit) are no longer
output, and transistor Trl 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 Termianl

1
No. :ConditionsTerminal voltage
13) 4AlT control module When the overdrlve
switch IS swrtched
ON 12v
iI14Overdrive switch
When the overdrive switch is switched ON 12v
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13-350AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
TROUBLESHOOTINGMlBEBoa

The auto-cruise control system performs control functions for
the setting or cancellation of the fixed-speed driving speed based upon the data provided by input signals. As a result,
when the auto-cruise control system is canceled by abnormal system operation, the cause of the cancellation is memorizedin a separate circuit by the ECU, thus providing the ECU with
the on-board diagnostic function by certain fixed patterns, as
well as the function of being able to check whether or not the
ECU’s input switches or sensor are normal. Thus, by effectively
using these function, the time required checking and repair can
be shortened.
TROUBLESHOOTING QUICK-REFERENCE CHART
Auto-cruise control system is canceled
when cancellation not wanted. ECU: Electronic control unit
Can the auto-cruise
control system be set
Set the auto-cruise con-
trol system and conduct
a road test.
No (new
normal)
.
Check whether or not, then, the vehicle was driven on a steep
slope.
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AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
NOTE
13-351
Auto-cruise control system cannot be set.
This chart is to be used, then, for troubleshooting if it is not
possible to use the on-board diagnostic for checking.
Prepare to conduct input check.
Where codesNo.21,22, 23, 25 and 26,displayed when,with the vehicle stationary,
the input check codes were recalled?Damaged or disconnected wiring of the ECU power-supply cir-
l Damaged or disconnected wiring of the SET or RESUMEswitch (Go to check chart 2 and 3.)l Damaged or disconnected wiring of the stop light switch,clutch pedal position switch or park/neutral position switch (Go
1 Are the results of all input checks normals?
YesNo
ck the auto-cruise vacuum pump circuit.1 (Go to check chart No.5.)
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Check results
’Probable cause RemedyCheck chartNo.
Code 21 remains even though SETswitch is set to OFF. SET switch ON mal-function
SET switch input line
short-circuitF,I~JI;? the control
Repair the harness.
No. 2
Code 22 remains even though RE-SUME switch is set to OFF. RESUME switch ON
Replace the controlNo.3malfunctionswitch.
RESUME switch inputRepair the harness.line short-circuit
Code 23 is not canceled even if theMalfunction of stopReplace stop lightNo.6
stop light switch is turned OFF by light switch circuit.switch or repair har-
releasing the brake pedal.
ness.
Code 25 does not disappear, and
Malfunction of theCheck or repair theNo.4
code 24 does not appear, evenvehicle-speed sensor vehicle speed sensorthough vehicle speed reaches appro-circuit (damaged or dis-circuit.ximately 40 km/h (25 mph) or higher.connected wiring, orshort-circuit)
Code 26 is not canceled even if the Malfunction of clutch
Replace clutch pedalNo.8clutch pedal position switch is turnedpedal position switchposition switch or repairOFF by releasing the clutch pedal.
circuit.harness.
Code 26 is not canceled even if the
Malfunction of park/Replace park/neutralNo. 7
select lever is moved to anything but neutral position ,switchposition switch or repair
v. P .circuit.harness.
NOTE
If the results of the check of the auto-cruise vacuum pump
circuit (check chart No. 5) and of the auto-cruise vacuum pump
and actuator itself
(P.13-401.) reveal no abnormal condition, re-
place the electronic control unit (ECU).

13-352AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
Trouble symptomProbable causeCheck chart No.
Remedy
l The set vehicle speed varies Malfunction of the ve-No.4Repair the vehicle speegreatly upward or downward.hicle speed sensor cir-l “Hunching” (repeated alternatingsensor system, or re-witplace the part.
acceleration and deceleration) oc- curs after setting is made.
Malfunction of the spee-
dometer cable or spee-
dometer drive gear
Auto-cruise vacuum
No.5Repair the auto-cruisepump circuit poor con-vacuum pump or replactactthe part.
Malfunction of the auto-cruise vacuum pump Malfunction of the ECU
-Replace the ECU.
The auto-cruise control system is not Damaged or discon-If the input check code Repair the harness or rezanceled when the brake pedals is netted wiring of the stopNo.23 indicates a mal-
depressed.light switch input circuit; function. No.6place the stop light
switch.
brake switch (for auto-cruise control) malfunc-
tion (short-circuit)
Auto-cruise vacuum
No.5Repair the harness or repump drive circuit short- place the auto-cruise va
circuit.cuum pump.
Malfunction of the ECU
-Replace the ECU.
The auto-cruise control system is not Damaged or discon-If the input check code
Repair the harness, or:anceled when the clutch pedal is netted wiring of clutchNo.26 indicates a mal-repair or replace thedepressed. (vehicles with a manual
pedal position switchfunction. No.8clutch pedal position
ransaxle)input circuitswitch.
It is canceled, however, when theIrake pedal is depressed.) Clutch pedal position
switch improper installa-
tion (won’t switch ON)
Malfunction of the ECU
-Replace the ECU.
*he auto-cruise control system is not Damaged or discon-If the input check code
Repair the harness, or:anceled when the shift lever is netted
wiring of park/No.26 indicates a mal-repair or replace the
noved to the “N” position. (vehicles neutral position switchfunction. No.7park/neutral position
vith an automatic transaxle)input circuit switch.t is canceled, however, when thebrake pedal is depressed.)
Improper adjustment of
park/neutral position
switch
Malfunction of the ECU-Replace the ECU.
anc$ decelerate by using the SET Temporary damaged orNo.2Repair the harness or re-disconnected wiring of
SET switch input circuitplace the SET switch.
Auto-cruise vacuumNo.5Repair the harness or re-pump circuit poor con-
tactplace the auto-cruise va-
cuum pump and actua-
tor.Malfunction of the auto-cruise vacuum pump
and actuator (including
clogging of negative
pressure passage)
Malfunction of the ECU-Replace the ECU.
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AUTO-CRUISE CONTROL SYSTEM - Troubleshooting13-353
Trouble symptom
Probable causeCheck chart No.Remedy
Cannot accelerate or resume speed
No.3
by using the RESUME switch. Damaged or discon- netted wiring, or short-
Repair the harness orcircuit, of RESUMEreplace the RESUMEswitch.
switch input circuit
Auto-cruise vacuum
No. 5Repair the harness orpump circuit poor con-replace the auto-cruisetactvacuum pump and
actuator.
Malfunction of the auto-cruise vacuum pump
and actuator (including
air leak from negative
pressure passage)
Malfunction of the ECU-Replace the ECU,
4uto-cruise control system can be Malfunction of theNo.4Repair the vehicle-set while traveling at a vehicle speed vehicle-speed sensorspeed sensor system,3f less than 40 km/h (25 mph), orcircuit‘or replace the part.
there is no automatic cancellation at
that speed.
Malfunction of thespeedometer cable orthe speedometer drivegear
The indicator light of combination
neter does not illuminate. But auto-cruise control system is
iormal.)
Malfunction of the ECU-Replace the ECU.
Damaged or discon--Repair the harness ornetted bulb of indicatorreplace the bulb.light
Harness damaged ordisconnected
vlalfunction of control function by Malfunction of circuit re-No. 9Repair the harness orIN/OFF switchrng of ELC 4 ATlated to accelerator
replace the part.accelerator switchswitch OFF function
Non-operation of torque converter
:lutch, 2nd gear hold, etc.) Malfunction of the ECU
Overdrive is not canceled during Malfunction of circuit re-No. 10Repair the harness or
ixed speed driving. lated to overdrive can-replace the part.cellation, or malfunction\lo shift to overdrive during manualIriving.
of ECU
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13-354AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
CHECK CHART 1. CHECKING THE CONTROL UNIT POWER SUPPLY CIRCUIT
IgnitionswitchI
Cruise-control
switchI(8)
pmTzREq
4 atAuto-cruise control unit
13A0377
Description of operation
When the cruise control switch (CRUISE) is switched ON whilethe ignition switch is ON, current flows to the ignition swrtch(IG,), to fuse No.(ll) of the junction block, and to the
cruise-control switch (MAIN switch), the control unit, and to
ground.When the ignition switch is turned OFF, the MAIN switch in thecruise control switch is also turned OFF.
Troubleshooting hint ECU terminal voltage
Terminal SignalConditions TerminalNo.voltage
2Control unitWhen the cruise-Battery
power supply control switch positive
(CRUISE) isvoltage
switched ON.
6. 8Control unitgroundAt all timesov
NOTEl :The connector Nos. in Section “AUTO-CRUISE CONTROL RELATED HARNESSES” and the connector names in the
junction block are represented.
(Applicable on the next page and subsequence.)
2. CHECKING THE SET SWITCH
I
Auto-cruise ’control unitT
v“17 3
A-3SETCrulse-OFFcontrolTONswitch
>: 13
63)
13AO386Description of operation
When the SET switch is switched ON (at the vehicle speed desired to be maintained, and with the CRUISE switch of the
cruise-control switches ON) that vehicle speed is maintained as
a constant speed.
Furthermore, the constant speed is gradually reduced (the “coasting” feature) when the SET switch is pressed and held
while the vehicle is traveling at the previously set constant
speed, and, when the SET switch is released, the vehicle thenmaintains that newly set constant speed (the speed at which
the SET switch was released).
Current flows to the control
unit. the cruise control switch
(“SET”), and to ground.
Troubleshooting hint
Diagnostic-No.15 (automatically cancelled)
ECU terminal voltage
Terminal SignalConditions TerminalNo.voltage
17SET switch
When the SETovswitch is switchedON.
When the SET
;yv$h is swrtched Battery
positive
voltage
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AUTO-CRUISE CONTROL SYSTEM - Troubleshooting13-355
3. CHECKING THE RESUME SWITCH CIRCUIT
Auto-cruisecontrol unit
--f
Y
Cruise-control
switch
Description of operation
The set speed (before cancellation) resumes when the RE- SUME switch is
swrtched ON, even if the constant-speed
control has been cancelled.That speed will not resume, however, even if the RESUMEswitch is switched ON, if the CRUISE switch is switched OFFand if the vehicle speed decreases to 40 km/h (25 mph) orlower.
In addition, when the RESUME is switched ON and held whi!ethe vehicle is traveling at a constant speed, the vehicle speedwill 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.
Troubleshooting hint
Diagnostic-No.1 5 (automatically cancelled)
ECU terminal voltage 13AO382
Terminal
Signal ConditionsTermrnalNo.voltage
18RESUME
When the RESUMEOVswrtchswitch is switchedON.
When the RESUME
Batteryswitch is switchedpositiveOFF.voltaae
4. CHECKING THE VEHICLE-SPEED SENSOR CIRCUIT
Auto-cruisecontrol unit
Combinationmeter
Junction
block
(6)
Description of operation
The vehicle-speed sensor is installed within the speedometer; itsends to the controlunit pulse signals that are proportional tothe rotatron speed (i.e., the vehicle speed) of the transaxle’soutput gear.
This vehicle-speed sensor IS the reed switch type of sensor; itgenerates four pulse signals for each rotation of the speedo-
meter’s driven gear.
Troubleshooting hint
Diagnostic-No.12 (automatically cancelled)
ECU terminal voltage
TerminalSignal Conditions
TerminalNo.voltage
19Vehicle-speedMove the vehicleov-0.7vsensorforward slowly.tFlashingJ3V-higher
13A0381
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13-356AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
5. CHECKING THE AUTO-CRUISE CONTROL VACUUM PUMP Description of operation
Hold modeWhen the SET switch is turned ON by the driver turning theCRUISE switch ON when a determined speed is reached, thecontrol unit receives a set signal, and turns the auto-cruisevacuum 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.
Ignitionswitch
Auto-cruise
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 release
(10)
control ’ “”unit13AO376
valve ON (valve is closed)
Deceleration mode
When the SET switch is held down, the control unit receives a
set srgnal and it not only turns the auto-cruise vacuum pumpmotor and control valve OFF (valve is opened) but also turns therelease 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-cruise
vacuum pump motor OFF but also turns the control valve andrelease valve OFF (valve is opened).
Troubleshooting hint
Diagnostic-No.1 1 (automatically cancelled)
ECU terminal voltage
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AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
6. CHECKING THE STOP LIGHT SWITCH CIRCUIT13-357
Stop lrght
Sub fusible link @I
Stop lrght
Auto-cruisecontrol unit 13AQ375
Description of operation
When the brake pedal is depressed during constant-speed
travel, the stop light
swrtch’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 isdiscontinued within the control unit, thereby canceling theconstant-speed travel.
The flow of current is from the sub fusible link @ to fuse No. @Iof the junction block, the stop light switch, and the control unit.
Troubleshooting hint
ECU terminal voltage
TerminalSignal ConditionsTerminalNo.voltage
15Stop light
When the brake Batteryswitch (loadpedal is depressed.positive
side)voltage
When the brakeovpedal is notdepressed.
NOTENC: Indicates ON at all times. (For cruise control)
NO: Indicates OFF at all times. (For stop light)
7. CHECKING THE PARK/NEUTRAL POSITION SWITCH CIRCUIT Description of operation
The park/neutral position switch also functions as the switch
for the starter. If the selector lever is moved to the “N”
pos-ition during constant-speed travel, current flows to the con-trol unit, park/neutral position switch, starter motor, and to
ground; the cancel signal is therefore input to the controlunit, thus canceling the constant-speed travel.
Troubleshooting hint
ECU terminal voltage
(I)
ia
Starter
motor
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13-358AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
8. CHECKING THE CLUTCH PEDAL POSITION SWITCH CIRCUIT
13A0378
Description of operation If the clutch pedal is pressed when driving at a constant
speed, the clutch pedal position 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 pedal position switch junction block from the control
unit and to ground.
Troubleshooting hint
ECU terminal
voltage
Terminal Signal Conditions
TerminalNo.voltage
1Clutch medalWhen the clutchov
Iposition switchpedal is depressed.IWhen the clutch
pedal is not
depressed.Battery
positive
voltage
9. CHECKING THE CIRCUITS RELATED TO THE ACCELERATOR SWITCH OFF FUNCTION
>
Ignition switch
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 duringconstant-speed driving in order not to interfere with the functionof the automatic transaxle.
Troubleshooting hint ECU terminal voltage
TerminalNo.Signal ConditionsTerminalvoltageII3Control unit
At all times Battery
power supply positive
voltage
I gAccelerator
switch
NOTENC: Indicates ON at all time
1 Not rn operation / OFF ) ON 1
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