1997 MITSUBISHI TRITON ECU

MPI ± Troubleshooting13A-21
INSPECTION CHART FOR TROUBLE SYMPTOMS13100880217
Trouble symptomInspection
procedure
No.Reference page
Communication
with MUT-IIis
Communication with all systems is not possible.113A-23
with MUT-II is
impossible.
Communication with engine-ECU only is not possible.213A-24
Engine warning
lamp and
relatedparts
The engine warning lamp does not illuminate right after the
ignition switch is turned to the ON position.313A-25
related partsThe engine warning lamp remains illuminating and never goes
out.413A-25
StartingNo initial combustion (starting impossible)513A-26
Initial combustion but no complete combustion
(starting impossible)613A-27
Long time to start (improper starting)713A-28
Idling stability
(Improper idling)
Unstable idling (Rough idling, hunting)813A-29
(Im ro er idling)
Idling speed is high. (Improper idling speed)913A-30
Idling speed is low. (Improper idling speed)1013A-31
Idling stability
(Engine stalls)
When the engine is cold, it stalls at idling. (Die out)1113A-32
(Engine stalls)
When the engine becomes hot, it stalls at idling. (Die out)1213A-33
The engine stalls when starting the car. (Pass out)1313A-34
The engine stalls when decelerating.1413A-34
DrivingHesitation, sag or stumble1513A-35
The feeling of impact or vibration when accelerating1613A-35
The feeling of impact or vibration when decelerating1713A-36
Poor acceleration1813A-36
Surge1913A-37
Knocking2013A-37
Dieseling2113A-37
Too high CO and HC concentration when idling2213A-38

MPI ± Troubleshooting13A-24
INSPECTION PROCEDURE 2
MUT-II communication with engine-ECU is impossible.
Probable cause
One of the following causes may be suspected.

No power supply to engine-ECU.

Defective earth circuit of engine-ECU.

Defective engine-ECU.

Improper communication line between engine-ECU and MUT-II

Malfunction of engine-ECU power supply circuit

Malfunction of engine-ECU

Open circuit between engine-ECU and diagnosis
connector


Malfunction of engine-ECU power supply circuit

Malfunction of engine-ECU

Malfunction of immobilizer-ECU

Open circuit between immobilizer-ECU and diagnosis
connector

Open circuit between engine-ECU and immobilizer-
ECU
OK
Ye s
NG

Check the following connector. C-19NG
Repair
Check trouble symptom.
NG
Check the harness wire between engine-ECU and diagnosis con-
nector.OKCheck the harness wire
between engine-ECU and
earth.NG
Repair
OK
Check the power supply and ignition switch-IG system. (Refer to
P.13A-39, INSPECTION PROCEDURE 23.)

Repair
OKCheck the harness wire
between engine-ECU and
earth.NG
Repair
OK
Check the power supply and ignition switch-IG system. (Refer to
P.13A-39, INSPECTION PROCEDURE 23.)
NG
Check the harness wire between engine-ECU and immobilizer-
ECU.
OK
Check trouble symptom.
Check the following connectors. C-19, C-36NG
Repair
Is communication possible between the MUT-II and the immobilizer-
ECU?NoCheck the diagnosis line between the immobilizer-ECU and the
MUT-II, and repair if necessary. (Refer to GROUP 54 ± Ignition
Key and Immobilizer.)
NG
Repair

MPI ± Troubleshooting13A-25
INSPECTION PROCEDURE 3
The engine warning lamp does not illuminate right after
the ignition switch is turned to the ON position.
Probable cause
Because there is a burnt-out bulb, the engine-ECU causes the engine warning lamp
to illuminate for five seconds immediately after the ignition switch is turned to ON.
If the engine warning lamp does not illuminate immediately after the ignition switch
is turned to ON, one of the malfunctions listed at right has probably occurred.
Burnt-out bulb

Defective warning lamp circuit

Malfunction of the engine-ECU
MUT-II Data list
16 engine-ECU power supply voltage (Refer to P.13A-58.)NGCheck the engine-ECU power supply and earth circuit.
(Refer to P.13A-53, INSPECTION PROCEDURE 42.)
OK
Measure at the engine-ECU connector C-50.

Disconnect the connector, and measure at the harness side.

Earth the terminal No. 36.
OK:The engine warning lamp illuminates.OKCheck the following
connector. C-50.NG
Repair
OK
Check trouble symptom.
NG
Replace the engine-ECU.
NG
Check a burnt-out bulb.NG
Replace
OK
Measure at the combination meter connector C-06.

Disconnect the connector, and measure at the harness side.

Voltage between 43 and earth (Ignition switch: ON)
OK:System voltageNGCheck the engine warning lamp power supply circuit, and repair
if necessary.
OK
Check the following connectors.
C-04, C-06, C-19, C-50NG
Repair
OK
Check trouble symptom.NGCheck the harness wire between combination meter and engine-
ECU, and repair if necessary.
INSPECTION PROCEDURE 4
The engine warning lamp remains illuminating and never
goes out.
Probable cause
In cases such as the above, the cause is probably that the engine-ECU is detecting
a problem in a sensor or actuator, or that one of the malfunctions listed at right has
occurred.
Short-circuit between the engine warning lamp and
engine-ECU

Malfunction of the engine-ECU
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES
No
Measure at the combination meter connector C-04.

Disconnect the connector, and measure at the harness side.

Disconnect the engine-ECU connector

Continuity between 8 and earth
OK:No continuityNGCheck the harness wire between combination meter and engine-
ECU connector, and repair if necessary.
OK
Replace the engine-ECU.

MPI ± Troubleshooting13A-26
INSPECTION PROCEDURE 5
No initial combustion (starting impossible)
Probable cause
In cases such as the above, the cause is probably that a spark plug is defective,
or that the supply of fuel to the combustion chamber is defective.
In addition, foreign materials (water, kerosene, etc.) may be mixed with the fuel.
Malfunction of the ignition system

Malfunction of the fuel pump system

Malfunction of the injectors

Malfunction of the engine-ECU

Malfunction of the immobilizer system with immobilizer system>

Foreign materials in fuel
Check battery voltage when cranking.
OK:8 V or higherNGCheck the battery. (Refer to GROUP 54 ± Battery.)
OK
Is immobilizer-ECU diagnosis code displayed? immobilizer system>Ye sCheck the immobilizer.
(Refer to GROUP 54 ± Ignition Key and Immobilizer.)
No
MUT-II: Inspection of no initial combustion.
(Refer to P.13A-47, INSPECTION PROCEDURE 34.)
OK
Can any sound be heard from the injectors when cranking?NGCheck the injector system. (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Ignition system: Inspection of no initial combustion.
(Refer to P.13A-47, INSPECTION PROCEDURE 35.)
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle service.)

Check if the injectors are clogged.

Check if foreign materials (water, alcohol, etc.) got into fuel.

Check the compression pressure.

Check the immobilizer system. (Refer to GROUP 54 ± Ignition Key and Immobilizer.)

MPI ± Troubleshooting13A-27
INSPECTION PROCEDURE 6
Initial combustion but no complete combustion
(starting impossible)
Probable cause
In such cases as the above, the cause is probably that the spark plugs are generating
sparks but the sparks are weak, or the initial mixture for starting is not appropriate.
Malfunction of the ignition system

Malfunction of the injector system

Foreign materials in fuel

Poor compression

Malfunction of the engine-ECU
Check battery voltage when cranking.
OK:8 V or higherNGCheck the battery. (Refer to GROUP 54 ± Battery.)
OK
MUT-II: Check if uncompleted combustion occurs.
(Refer to P.13A-48, INSPECTION PROCEDURE 36.)
OK
Can any sound be heard from the injectors when cranking?NGCheck the injector system, (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Is starting good if the engine is cranked with the accelerator pedal
slightly depressed?Ye sCheck ISC servo for op-
eration sound.
(Refer to P.13A-90.)NGCheck the ISC servo sys-
tem. (Refer to P.13A-45,
INSPECTION PROCE-
DURE 31.)
OK

Clean the throttle valve area. (Refer to P.13A-78.)

Check and adjust the fixed SAS. (Refer to P.13A-79.)
No
Check the ignition timing when cranking.
OK:Approx. 5BTDCNGCheck that the distributor is installed properly.
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check if the injectors are clogged.

Check the compression pressure. (Refer to GROUP 11 ± On-vehicle Service.)

Check fuel lines for clogging.

Check if foreign materials (water, alcohol, etc.) got into fuel.

MPI ± Troubleshooting13A-33
INSPECTION PROCEDURE 12
When the engine is hot, it stalls at idling. (Die out)
Probable cause
In such cases as the above, the cause is probably that ignition system, air/fuel mixture,
idle speed control (ISC) or compression pressure is defective.
In addition, if the engine suddenly stalls, the cause may also be a defective connector
contact.
Malfunction of the ignition system

Malfunction of air-fuel ratio control system

Malfunction of the ISC system

Drawing air into intake system

Improper connector contact
Were the battery terminals disconnected?Ye sAfter warming-up, let the engine run at idling for 10 minutes.
No
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
Check the ISC servo for operation sound. (Refer to P.13A-90.)NGCheck the ISC servo system.
(Refer to P.13A-45, INSPECTION PROCEDURE 31.)
OK
Check the injector for operation sound.NGCheck the injector system. (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Does the engine stall right after the accelerator pedal is released?Ye sClean the throttle valve
area. (Refer to P.13A-78.)Check and adjust the
fixed SAS.
(Refer to P.13A-79.)
No
Does the engine stall easily again?NoWhile carrying out an intermittent malfunction simulation test (Refer
to GROUP 00 ± Points to Note for Intermittent Malfunctions.), check
for sudden changes in the signals shown below.

Crank angle sensor signal

Air flow sensor signal

Injector drive signal
Primary and secondary
ignition signal

Fuel pump drive signal

Engine-ECU power supply
voltage
Ye s
MUT-II: Engine stalling inspection when the engine is warm and
idling. (Refer to P.13A-50, INSPECTION PROCEDURE 39.)
OK
Check the ignition timing.
(Refer to GROUP 11 ± On-vehicle Service.)NGCheck that the distributor is installed properly.
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check if the injectors are clogged.

Check the compression pressure. (Refer to GROUP 11 ± On-vehicle Service.)

Check if foreign materials (water, alcohol, etc.) got into fuel.

MPI ± Troubleshooting13A-39
INSPECTION PROCEDURE 23
Power supply system and ignition switch-IG system
Probable cause
When an ignition switch ON signal is input to the engine-ECU, the engine-ECU turns
the control relay ON. This causes battery voltage to be supplied to the engine-ECU,
injectors and air flow sensor.
Malfunction of the ignition switch

Malfunction of the control relay

Improper connector contact, open circuit or
short-circuited harness wire

Disconnected engine-ECU earth wire

Malfunction of the engine-ECU
Check the control relay. (Refer to P.13A-86.)NG
Replace
OK
Measure at the control relay connector C-53.

Disconnect the connector, and measure at the harness side.

Voltage between 3, 4 and earth
OK:System voltageNGCheck the harness wire between battery and control relay connector,
and repair if necessary.
OK
Check the engine-ECU power supply and earth circuit.
(Refer to P.13A-53, INSPECTION PROCEDURE 42.)

MPI ± Troubleshooting13A-40
INSPECTION PROCEDURE 24
Fuel pump system
Probable cause
The engine-ECU turns the control relay ON when the engine is cranking or running,
and this supplies power to drive the fuel pump.
Malfunction of the fuel pump relay

Malfunction of the fuel pump

Improper connector contact, open circuit or
short-circuited harness wire

Malfunction of the engine-ECU
Check the fuel pump operation. (Refer to P.13A-84.)NGCheck the fuel pump circuit.
(Refer to P.13A-53, INSPECTION PROCEDURE 43.)
OK
Check the fuel pump relay. (Refer to P.13A-86.)NG
Replace
OK
Measure at the fuel pump relay connector C-54.

Connect the connector.

Voltage between 1 and earth

MUT-II Actuator test: Fuel pump drive
OK:System voltageNGCheck the fuel pump drive control circuit.
(Refer to P.13A-54, INSPECTION PROCEDURE 44.)
OK
Check the harness wire between fuel pump relay connector and
fuel pump drive terminal, and repair if necessary.
INSPECTION PROCEDURE 25
Idle position switch system
Probable cause
The idle position switch inputs the condition of the accelerator pedal, i.e. whether
it is depressed or released (HIGH/LOW), to the engine-ECU.
The engine-ECU controls the idle speed control servo based on this input.
Maladjustment of the accelerator pedal

Maladjustment of the fixed SAS

Maladjustment of the idle position switch and throttle
position sensor

Improper connector contact, open circuit or
short-circuited harness wire

Malfunction of the engine-ECU
Check the idle position switch. (Refer to P.13A-87.)NGReplace
OK
Measure at the throttle position sensor connector A-47.

Disconnect the connector, and measure at the harness side.

Voltage between 2 and earth (Ignition switch: ON)
OK:4 V or higher

Continuity between 1 and earth
OK:ContinuityNGCheck the following
connector. C-51NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between engine-ECU and throttle position
sensor connector.
OK
Replace the engine-ECU.
NG
Repair
OK
Check the following
connector. A-47NG
Repair
OK
Check trouble symptom.
NG
Replace the engine-ECU.