1989 MITSUBISHI GALANT Service Repair Manual

AUTO-CRUISE CONTROL SYSTEM - Troubleshooting13-347
6-3. CHECKING THE CLUTCH PEDAL POSITION SWITCH CIRCUIT
Ignition
switch
Junction block
ECU
NOTENO: OFF at all time
Description of operation If the clutch pedal is depressed during constant-
speed travel, the contacts of the clutch pedal position switch close, with the result that the
cancel signal is sent to the control unit, so that
the current to the electromagnetic clutch of
Troubleshooting hint
Diagnostic-No.16 (automatically cancelled)
ECU temrinal voltage the actuator is discontinued within the control
unit, thereby canceling the constant-speed travel.
The flow of current is to the ignition switch (IGI),
fuse No. (9) of the junction block, the
clutch pedal position switch, and the control unit.
/ Te;z,nal 1Conditions Terminal voltage
Clutch pedal position
switch When the clutch pedal is depressed
When the clutch pedal is not depressed12v
ov
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13-348AUTO-CRUISE CONTROL SYSTEM - Troubleshooting
7. CHECKING THE CIRCUITS RELATED TO THE ACCELERATOR SWITCH
OFF FUNCTION
(16)
[ml
Ignition
switch
Junction
block
r------_--- ___--- ---
4
A/T
control
module
NOTENC: ON at all time Iescription
of operation
The accelerator switch is a switch that
detect-s the
operational status of the accelerator pedal; it is one of the sensors of the automatic transaxle.
Because the status of the accelerator pedal during constant-speed driving is non-operational, the ground circuit (transistor Tr2) of the accelerator
switch is switched OFF only during constant-speed
driving in order not to interfere with the function of
the automatic transaxle.
Troubleshooting hint ECU terminal voltage
Terminal
1
No. , SignalConditions
Terminal voltage
6’ Control unit power sup-
At all times12vply (IG2)
16
Accelerator switch When the accelerator pedal is depressed
o
v
When the accelerator pedal is not depressed
12v
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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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