check engine light MITSUBISHI MONTERO 1991 Owner's Manual

2.6L Engine ........................................... 45
2.6L Optional ......................................... 45
3.0L V6 ........................................... (1) 24
3.5L V6 ........................................... ( 1) 24
( 1) - Check hood clearance on 1986 and newer models.









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CAUTIONS & WARNINGS
SUPPLEMENTAL RESTRAINT SYSTEM (SRS) AIR BAG SYSTEM
NOTE: See the AIR BAG RESTRAINT SYSTEM article in the
ACCESSORIES/SAFETY EQUIPMENT Section.
The SRS has no user-servicable parts. Always have servicing
done by an authorized dealer.
When performing maintenance on air bag equipped vehicles
always observe proper safety precautions.
WARNING: To avoid injury from accidental air bag deployment, read and
carefully follow all warnings and service precautions. See
appropriate AIR BAG RESTRAINT SYSTEM article in the
ACCESSORIES/SAFETY EQUIPMENT section.
CAUTION: Disconnect negative battery cable before servicing any air
bag system, steering column or passenger side dash
component. After any repair, turn ignition key to the ON
position from passenger's side of vehicle in case of
accidental air bag inflation
ANTI-LOCK BRAKE SYSTEM (ABS)
CAUTION: Never mix different diameter tires. On loose or uneven
surfaces, the ABS system may require longer stopping
distances than conventional brake systems. Exercise caution
when removing mud or snow from the wheels so as not to
damage the ABS wiring or speed sensors.
BATTERY WARNING
WARNING: When battery is disconnected, vehicles equipped with
computers may lose memory data. When battery power is
restored, driveability problems may exist on some vehicles.
These vehicles may require a relearn procedure. See
appropriate COMPUTER RELEARN PROCEDURES article in the
GENERAL INFORMATION section below.
REPLACING BLOWN FUSES
Before replacing a blown fuse, remove ignition key, turn off
all lights and accessories to avoid damaging the electrical system. Be
sure to use fuse with the correct indicated amperage rating. The use
of an incorrect amperage rating fuse may result in a dangerous
electrical system overload.
BRAKE PAD WEAR INDICATOR
Indicator will cause a squealing or scraping noise, warning
that brake pads need replacement.

Light comes on with the ignition switch in the "ON" position
as a bulb check, but should go out shortly after engine is started. If
light remains on or comes on while driving, it indicates low oil
pressure and possible system malfunction. Have the system checked and
serviced immediately. Do not operate vehicle until cause is located
and corrected.
ALTERNATOR WARNING LIGHT
Light comes on with the ignition switch in the "ON" position
as a bulb check and goes out after engine is started. If light remains
on or comes on while driving, it indicates possible fault in the
electrical charging system. The alternator belt may be loose or
broken. Have the system checked and serviced promptly. Do not drive
vehicle if alternator belt is loose or broken.
"BRAKE" WARNING LIGHT
Light comes on with the ignition switch in the "ON" position
as a bulb check and goes out after engine is started. Light will also
come on with the parking brake fully or partially engaged. If light
remains on or comes on at any other time, it indicates low brake fluid
level in the master cylinder reservoir or the parking brake switch may
be damaged. Have the system checked and serviced immediately if brake
fluid level is low. Do not continue driving if further trouble is
experienced.
"CHECK ENGINE" WARNING LIGHT (IF EQUIPPED)
Light is designed to come on briefly with the ignition switch
in the "ON" position as a bulb check. If light remains on or comes on
while driving, it indicates fault in an exhaust gas related component
and the system is not functioning properly. Have the system checked
and serviced as soon as possible.
"MAINTENANCE REQUIRED" WARNING LIGHT (IF EQUIPPED)
Light comes on at 50,000 miles, 80,000 miles, 100,000 miles
and 120,000 miles (150,000 miles on 1990-91 models) as a service
reminder that it is time for the periodic maintenance of the emission
control system. Have the system inspected and serviced as necessary
when light comes on. Continued operation of vehicle without having
system serviced after warning light comes on may adversely affect
proper performance of the emission control system. Reset warning
light, after the system has been checked, by pushing the reset switch
in front of the combination meter. Remove the warning light bulb after
the last maintenance service at 120,000 miles (150,000 miles on 1990-
91 models).
"A/T TEMPERATURE" WARNING LIGHT (IF EQUIPPED)
Light comes on when the automatic transmission fluid
temperature becomes abnormally high. If light comes on, reduce engine
speed, stop car and put it in "P" (Park) position. Leave engine
running until light goes out. Normal vehicle operation may be resumed
after light has gone out. If light does not go out, have the system
checked and serviced as necessary.
WHEEL LOCK INDICATOR LIGHT (IF EQUIPPED)
Light comes on when automatic free-wheeling hubs are locked.
If ignition is turned off, indicator light will not come on when

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G - T E STS W /C O DES
1991 Mitsubishi Montero
1990-91 ENGINE PERFORMANCE
Chrysler Motors/Mitsubishi Self-Diagnostics
Dodge; Colt, Colt Vista, Colt Wagon
Eagle; Summit
Mitsubishi; Eclipse, Galant, Mirage, Montero, Precis (1990)
Plymouth; Colt, Colt Vista, Colt Wagon
INTRODUCTION
If no faults were found while performing F - BASIC TESTING,
proceed with self-diagnostics. If no fault codes or only pass codes
are present after entering self-diagnostics, proceed to H - TESTS W/O
CODES article for diagnosis by symptom (i.e. ROUGH IDLE, NO START,
etc.).
SELF-DIAGNOSTIC SYSTEM
Use Chrysler Motors code charts when using Chrysler's
Diagnostic Readout Box (DRB-II). If DRB-II is not available or if
working on a Mitsubishi Motors vehicle, system diagnosis can only be
accomplished using a voltmeter or appropriate scan tester. To diagnose
Chrysler Motors and Mitsubishi models using a voltmeter, see
ENTERING ON-BOARD DIAGNOSTICS (USING VOLTMETER) in this article.
SYSTEM DIAGNOSIS
SYSTEM DIAGNOSIS DESCRIPTION
NOTE: Chrysler Motors recommends using DRB-II to diagnose system.
Voltmeter usage has limited diagnostic capabilities but can
be used if DRB-II is not available or if working on a
Mitsubishi Motors vehicle.
The Engine Control Unit (ECU) monitors several different
engine control system circuits. If an abnormal input signal occurs, a
fault code is stored in ECU memory and given a fault code number. Each
circuit has its own fault number and message. A specific fault code
indicates a particular system failure, but it DOES NOT indicate that
cause of failure is necessarily within system. A fault code DOES NOT
condemn any specific component; it simply points out a probable
malfunctioning area. If a critical fault code is set, the ECU will
turn on CHECK ENGINE light. All fault codes except speed sensor are
considered critical.
Fault codes can be confirmed by using a voltmeter on Chrysler
Motors and Mitsubishi models or Chrysler's Diagnostic Readout Box
(DRB-II) on Chrysler Motors vehicles. See
ENTERING ON-BOARD DIAGNOSTICS (USING VOLTMETER) or ENTERING ON-BOARD
DIAGNOSTICS (USING DRB-II) in this article. By using the DRB-II, the
self-diagnostic capabilities of this system can simplify testing and
reduce diagnostic time.
System malfunctions encountered are identified as either hard
failures or intermittent failures as determined by the ECU.
HARD FAILURES
Hard failures cause CHECK ENGINE light to illuminate and
remain on until the malfunction is repaired. If light comes on and

remains on (light may flash) during vehicle operation, cause of
malfunction must be determined by using DIAGNOSTIC FAULT CHARTS (if
testing with voltmeter) or diagnostic CODE CHARTS (if testing with
DRB-II). If a sensor fails, ECU will use a substitute value in its
calculations to continue engine operation. In this condition, vehicle
is functional, but loss of good driveability may result.
INTERMITTENT FAILURES
Intermittent failures may cause CHECK ENGINE light to flicker
or illuminate and go out after the intermittent fault goes away.
However, the corresponding trouble code will be retained in ECU
memory. If related fault does not reoccur within a certain time frame,
related trouble code will be erased from ECU memory. Intermittent
failures may be caused by a sensor, connector or wiring related
problems. See INTERMITTENTS in H - TESTS W/O CODES article.
PRETEST INSPECTION
Before proceeding with diagnosis, the following precautions
must be followed:
* Vehicle must have a fully charged battery and functional
charging system.
* Visually inspect connectors and circuit wiring being worked
on.
* DO NOT disconnect battery or ECU. This will erase any fault
codes stored in ECU.
* DO NOT cause short circuits when performing electrical tests.
This will set additional fault codes, making diagnosis of original
problem more difficult.
* DO NOT use a test light in place of a voltmeter.
* When checking for spark, ensure coil wire is NO more than
1/4" from ground. If coil wire is more than 1/4" from ground,
damage to vehicle electronics and/or ECU may result.
* DO NOT prolong testing of fuel injectors. Engine may
hydrostatically (liquid) lock.
* When a vehicle has multiple fault codes, always repair lowest
number fault code first.
* If DRB-II is being used to diagnose system, always perform
verification test after repairs are made.
ENTERING ON-BOARD DIAGNOSTICS (USING VOLTMETER)
1) Before entering on-board diagnostics, refer to PRETEST
INSPECTION in this article. Turn ignition switch to OFF position.
Locate self-diagnostic connector. See SELF-DIAGNOSTIC TEST CONNECTOR
LOCATION table. Using an analog voltmeter, connect voltmeter positive
lead to self-diagnostic connector terminal No. 1 and negative lead to
terminal No. 12 (ground). See Fig. 6.
2) Turn ignition switch to ON position and disclosure of ECU
memory will begin. If 2 or more systems are non-functional, they are
indicated by order of increasing code number. Indication is made by
12-volt pulses of voltmeter pointer. A constant repetition of short
12-volt pulses indicates system is normal. If system is abnormal,
voltmeter will pulse between zero and 12 volts.
3) Signals will appear on voltmeter as long and short 12-volt
pulses. Long pulses represent tens; short pulses represent ones. For
example 4 long pulses and 3 short pulses indicates Code 43. See

44 (5) ..... Open or short in either ignition coil circuit
( 1) - Except Montero & Sigma.
( 2) - Will not turn on CHECK ENGINE light.
( 3) - 2.0L turbo only.
( 4) - California only. Except Sigma.
( 5) - Chrysler Motors models only.









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CLEARING CODES
Using DRB-II, from main menu select ADJUSTMENTS. Enter ERASE
FAULTS. Follow DRB-II instructions to accomplish this task. If DRB-II
is not available, fault codes may be cleared by disconnecting negative
battery cable for at least 10 seconds, allowing ECU to clear fault
codes.
TEST CHARTS
* PLEASE READ THIS FIRST *
NOTE: The following charts are supplied for Chrysler Motors
vehicles.
NS-1: TESTING IGNITION CIRCUIT - 1.5L
Fig. 7: Circuit Diagram NS-1 (1.5L) (1 of 2)
Fig. 8: Circuit Diagram NS-1 (1.5L) (2 of 2)

Inhibitor Switch (Automatic Transmission Only)
Inhibitor switch senses position of transmission select
lever, indicating engine load due to automatic transmission
engagement. Based on this signal, ECU commands ISC motor to increase
throttle angle, maintaining optimum idle speed.
Intake Air Temperature Sensor
Incorporated in airflow sensor assembly, this resistor-based
sensor measures temperature of incoming air and supplies air density
information to ECU.
Motor Position Sensor (MPS)
Incorporated in ISC motor (or separate unit on some models),
senses ISC motor plunger position and sends electrical signal to ECU.
Oxygen (O2) Sensor
Located in exhaust system, generates an output voltage.
Output voltage varies with oxygen content of exhaust gas stream. ECU
adjusts air/fuel mixture based on signals from oxygen sensor.
Power Steering Oil Pressure Switch
Detects increase in power steering oil pressure. When power
steering oil pressure increases, switch contacts close, signalling
ECU. ECU commands ISC motor, raising idle speed to compensate for drop
in engine RPM due to power steering load.
TDC Sensor
See CRANKSHAFT ANGLE & TDC SENSOR ASSEMBLY.
Throttle Position Sensor (TPS)
A variable resistor mounted on throttle body. ECU uses
voltage signal received from TPS to determine throttle plate angle.
Vehicle Speed Sensor
Located in speedometer in instrument cluster, uses a reed
switch to sense speedometer gear revolutions. ECU uses gear
revolutions to determine vehicle speed.
OUTPUT SIGNALS
NOTE: Vehicles are equipped with different combinations of
computer-controlled components. Not all components listed
below are used on every vehicle. For theory and operation on
each output component, refer to the system indicated in
brackets after component.
CHECK ENGINE Light
See SELF DIAGNOSTIC SYSTEM.
EGR Control Solenoid Valve
See EXHAUST GAS RECIRCULATION (EGR) CONTROL under EMISSION
SYSTEMS.
Fuel Injectors
See FUEL CONTROL under FUEL SYSTEM.
Fuel Pressure Control Solenoid Valve (Turbo Only)
See FUEL DELIVERY under FUEL SYSTEM.
Fuel Pressure Regulator
See FUEL DELIVERY under FUEL SYSTEM.
Fuel Pump Relay (MPI Control Relay)

EMISSION SYSTEMS
EXHAUST GAS RECIRCULATION (EGR) CONTROL
Federal (Non-Turbocharged)
To lower oxides of nitrogen (NOx) exhaust emissions, a non-
computer controlled exhaust gas recirculation system is used. EGR
operation is controlled by throttle body ported vacuum. Vacuum is
routed through thermovalve to prevent EGR operation at low engine
temperatures.
Spring pressure holds EGR valve closed during low vacuum
conditions (engine idling or wide open throttle). When vacuum pressure\
increases and overcomes EGR spring pressure, EGR valve is lifted and
allows exhaust gases to flow into intake manifold for combustion.
California & Turbocharged
ECU controls EGR operation by activating EGR control solenoid
valve according to engine load. When engine is cold, ECU signals EGR
control solenoid valve to deactivate EGR.
California models are equipped with an EGR temperature
sensor. When EGR malfunction occurs, EGR temperature decreases and ECU
illuminates CHECK ENGINE (malfunction indicator) light.
EGR Control Solenoid Valve
Denies or allows vacuum supply to EGR valve, based upon ECU
commands.
Thermovalve
Denies or allows vacuum supply to EGR valve based on coolant
temperature.
EVAPORATIVE CONTROL
Fuel evaporation system prevents fuel vapor from entering
atmosphere. System consists of a special fuel tank with vapor
separator tanks (if equipped), vacuum relief filler cap, overfill
limiter (2-way valve), fuel check valve, thermovalve (if equipped),
charcoal canister, purge control valve, purge control solenoid valve
and connecting lines and hoses.
Purge Control Solenoid Valve
When engine is off, fuel vapors are vented into charcoal
canister. When engine is warmed to normal operating temperature and
running above idle, ECU energizes purge control solenoid valve,
allowing vacuum to purge valve.
Canister vapors are then drawn through purge valve into
intake manifold for burning. Purge control solenoid valve remains
closed during idle and engine warm-up to reduce HC and CO emissions.
HIGH ALTITUDE CONTROL (HAC)
This system compensates for variations in altitude. When
atmospheric (barometric) pressure sensor determines vehicle is above
preset altitude, ECU compensates by adjusting air/fuel mixture and
ignition timing. If HAC system is inoperative, there will be an
increase in emissions.
PCV VALVE
Positive Crankcase Ventilation (PCV) valve operates in the
closed crankcase ventilation system. Closed crankcase ventilation

system consists of PCV valve, oil separator, breather and ventilation
hoses.
PCV valve is a one-way check valve, located in valve cover.
When engine is running, manifold vacuum pulls PCV valve open, allowing
crankcase fumes to enter intake manifold. If engine backfires through
intake manifold, PCV valve closes to prevent crankcase combustion.
SELF-DIAGNOSTIC SYSTEM
Self-diagnostic system monitors input and output signals. On
all models, codes can be read using analog voltmeter. On some models,
scan tool can be used to read codes. For additional information, see G
- TESTS W/ CODES article.
CHECK ENGINE Light
Also called Malfunction Indicator Light by manufacturer,
comes on when ignition is turned on. Light remains on for several
seconds after engine has started. If an abnormal input signal occurs,
light comes on and code is stored in memory. If an abnormal input
signal returns to normal, ECU turns light off but code remains stored
in memory until cleared. If ignition is turned on again, light will
not come on until ECU detects malfunction during system operation.
NOTE: ECU diagnostic memory is retained by direct power supply
from the battery. Memory is not erased by turning off
ignition but is erased if battery or ECU is disconnected.

PICKUP
1) Ensure engine idle is adjusted correctly. Ensure throttle
lever and throttle cable bracket are not bent. Pull lightly on inner
throttle cable.
2) While in closed throttle position, measure gap between
inner cable stopper and outer cable housing. Adjust cable as necessary
to obtain a gap of .031-.059" (.79-1.50 mm). See Fig. 4 (STEP 1).
Fig. 4: Adjusting Throttle Cable (Pickup)
Courtesy of Mitsubishi Motor Sales of America.
3) While holding throttle in wide open position, pull on
inner throttle cable. Adjust bell crank as necessary to obtain a gap
of 1.46-1.50" (37.08-38.10 mm) between inner cable stopper and outer
cable. See Fig. 4 (STEP 2).
4) With throttle fully closed, recheck gap between inner
cable stopper and outer cable housing. Gap should be .031-.059" (.79-
1.50 mm). See Fig. 4 (STEP 3). While holding throttle in wide open
position, pull on inner throttle cable. Check for a gap of 1.30-1.38"
(33.02-35.05 mm).
Montero Ensure throttle lever and throttle cable bracket
are not bent. Ensure distance between inner cable stopper end and dust
cover is 0-.04" (0-1.0 mm). See Fig. 5.
Fig. 5: Adjusting Throttle Cable (Montero)
Courtesy of Mitsubishi Motor Sales of America.
SHIFT LINKAGE

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TR O UBLE S H O OTIN G - B ASIC P R O CED URES

1991 M it s u bis h i M onte ro
GENERAL TROUBLE SHOOTING
* PLEASE READ THIS FIRST *
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
ACCESSORIES & ELECTRICAL
CHARGING SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC CHARGING SYSTEM TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Vehicle Will Not Dead battery Check battery cells,
Start alternator belt
tension and alternator
output
Loose or corroded battery Check all charging
connections system connections
Ignition circuit or switch Check and replace as
malfunction necessary









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Alternator Light Loose or worn alternator Check alternator drive
Stays On With drive belt tension and
Engine Running condition, See Belt
Adjustment in TUNE-UP
article in the
TUNE-UP section
Loose alternator wiring Check all charging
connections system connections
Short in alternator light See Indicator Warning
wiring Lights in STANDARD
INSTRUMENTS in the
ACCESSORIES &
EQUIPMENT section
Defective alternator stator See Bench Tests in
or diodes ALTERNATOR article
Defective regulator See Regulator Check in