1991 MITSUBISHI MONTERO engine

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

Fig. 2: Diagnostic Fault Chart (2 of 2)
Courtesy of Mitsubishi Motor Sales of America.
DIAGNOSTIC PROCEDURE (USING DRB-II)
DRB-II PROCEDURE
NOTE: When using diagnostic code charts, DO NOT skip any steps in
chart or incorrect diagnosis may result. Always check related
Technical Service Bulletins (TSB's).
Refer to ENTERING ON-BOARD DIAGNOSTICS (USING DRB-II) to
retrieve fault codes. If fault codes are NOT present and/or DRB-II is
used, proceed to one of the following tests:
* Go to NO START TEST 1 (NS-1) chart if a no-start condition
exists or engine stalls after start-up. Perform indicated
VERIFICATION PROCEDURE chart after repairs. Ensure charts
apply to engine being tested.
* Go to DRIVEABILITY TEST 1 (DR-1) chart if engine runs but has
performance problems. Perform indicated VERIFICATION

PROCEDURE chart after repairs. Ensure charts apply to engine
being tested.
DRB-II KEY FUNCTIONS
* YES or Down Arrow & NO or Up Arrow
Keys will move lines on screen up or down allowing you to
choose an item or scroll through all selections
available.
* F1 & F2 Keys
Keys are used to scroll through sensor displays.
* ATM Key
Key will return you to previous screen.
* ENTER Key
Allows you to select a test or display. The flashing
arrow must be on the display you wish to select. Pressing
ENTER in the sensor state will cause display to change
from a 3-line display to a 1-line display.
* F3 Key
Key is used to display a help screen. This key may be
used at any time.
* Number Keys
Keys are used for choosing a display or test by the
number for the test or display.
* READ/HOLD Key
Key is used to freeze any sensor display.
* MODE & ATM Key
Pressing MODE and ATM key at the same time will cause
DRB-II to reset to copyright screen.
ENTERING ON-BOARD DIAGNOSTICS (USING DRB-II)
* PLEASE READ THIS FIRST *
1) Before entering on-board diagnostics, refer to PRETEST
INSPECTION in this article. Turn ignition off. Locate self-diagnostic
connector. See SELF-DIAGNOSTIC TEST CONNECTOR LOCATION table in this
article. Using appropriate Mitsubishi cartridge and adapter, connect
DRB-II to diagnostic connector.
2) Ensure all accessories are off. Turn ignition on. All
character positions will illuminate and copyright information will
appear on screen for a few seconds.
3) If DRB-II screen displays an error message, refer to DRB-
II ERROR SCREENS in this article. The DRB-II will offer 4 menus:
VEHICLES TESTED, HOW TO USE, CONFIGURE and SELECT VEHICLE.
VEHICLES TESTED
Press "1" key or ENTER key when VEHICLES TESTED appears on
DRB-II. DRB-II shows models covered by cartridge. Screen will display
for 5 seconds and return to DRB-II menu. To return to DRB-II menu
sooner, press ATM key.
HOW TO USE
Press "2" key or press down arrow to display HOW TO USE
option and press ENTER. Press and hold F3 key. DRB-II displays
instructions for cartridge usage. To return to DRB-II menu, press ATM
key.
CONFIGURE

Press "3" key or press down arrow to display CONFIGURE option
and press ENTER. Configure allows user to customize DRB-II display.
For example, If metric system is more useful, select METRIC from the
menu. All selections in CONFIGURE option remain active until user
changes selection.
SELECT VEHICLE
1) This allows the user to enter information about vehicle
being tested. Usually, this option has more than one display screen.
Use ENTER key to enter vehicle information.
2) When all information about vehicle is entered, DRB-II will
display an information summary the technician has entered. DRB-II will
show an additional option marked CONFIRM. If information is correct,
press CONFIRM. DRB-II will display MAIN MENU.
MAIN MENU
The MAIN MENU represents all diagnostic functions available.
Functions are SYSTEM TESTS, READ FAULTS, STATE DISPLAYS, ACTUATOR
TESTS and ADJUSTMENTS. SYSTEM TESTS is NOT available.
READ FAULTS
This allows technician to read fault codes stored in ECU
memory.
STATE DISPLAYS
1) This allows technician to view conditions at signal level.
The 2 types of signals are analog and digital. Analog signals are
monitored at pins corresponding to vehicle harness splices (e.g. fuel
pump relay).
2) Digital signals correspond to data transmitted by the
system controllers. Both signals are displayed in common units (e.g.
temperature). Use up and down arrow keys on DRB-II to scroll through
displays available.
3) The following ENGINE state displays are available on DRB-
II:
* Module Information - This mode allows technician to read ECU
part number and application.
* Engine Sensors - This mode allows technician to look at
various engine sensors during engine operation.
* Inputs/Outputs - This mode allows technician to read input
and output states of various switches and sensors.
* Custom Display - This screen allows technician to set up
his/her own custom display. Two custom display screens can be
programmed into DRB-II.
* Minimum/Current/Maximum - The MIN/CURRENT/MAX display shows a
history of conditions for a specific sensor. When this option
is selected, maximum, current (static) and minimum values can\
be displayed for a specific sensor. To reset sensors to a
zero value, simply press ENTER key. This display may be used
to isolate intermittent faults. The MIN/CURRENT/MAX display
allows technician to observe operation of 6 different sensor
values. Information is displayed as a 3-digit number. The
first value displayed is the minimum reading, the second
number is the current reading and third valve is the maximum
reading. Typically sensors range between 2-252. Values less
than 2 or greater than 252 will usually indicate that a

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.









\









\









\









\









\









\






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)










\









\









\









\









\









\






DRBII
EGR Temp. Display Engine Conditions
160
F ........................................... Hot Idle
350F ................................ 25 MPH at 3,500 RPM
311F ................................ 55 MPH at 3,500 RPM








\









\









\









\









\









\






Fig. 66: Circuit Diagram DR-16 (1.5L) (1 of 2)
Fig. 67: Circuit Diagram DR-16 (1.5L) (2 of 2)

that all of the engine control systems are operating as they were
designed to. Therefore, they are not the cause of the driveability
problem.
The following additional items can not be overlooked as possible
causes of a driveability problem.
1. THROTTLE VALVE AREA - Dirt or ice buildup causing rough idle and
stalling.
2. ENGINE IGNITION TIMING - Must be set with timing terminal
grounded.
3. ENGINE VACUUM - Must be normal for your altitude.
4. ENGINE VALVE TIMING - To specifications.
5. ENGINE COMPRESSION - To specifications.
6. ENGINE P.C.V. SYSTEM - Must flow freely.
7. ENGINE EXHAUST SYSTEM - Must be free of any restrictions.
8. POWER BRAKE BOOSTER - No internal vacuum leaks.
9. TORQUE CONVERTER CONDITION - May cause very low power at breakaway
or high speed (Only 1 condition at a time).
10. FUEL CONTAMINATION - High alcohol or water content.
11. FUEL INJECTORS - Rough idle may be caused by injector wiring not
connected to correct injector.
12. ENGINE SECONDARY IGNITION CHECK - Abnormal scope patterns.
13. TECHNICAL SERVICE BULLETINS - Any that apply to vehicle.
14. All air intake piping and vacuum hoses must be in place and
secure. The proper air filter element must be used.
15. FUEL PRESSURE - Must be correct.
Specification: With no vacuum at the regulator:
48 PSI on V6 & non-turbo 4 Cyl. engines
36 PSI on turbo engines
NS-1: TESTING IGNITION CIRCUIT - 1.6L
Fig. 75: Circuit Diagram NS-1 (1.6L)

Fig. 167: Flow Chart DR-19 (1.6L)
DR-21: NO FAULT CODE MECHANICAL TEST - 1.6L
At this point in the driveability test procedure, you have
determined that all of the engine control systems are operating as
they were designed to. Therefore, they are not the cause of the
driveability problem.