1997 MITSUBISHI TRITON check engine

MPI ± General Information13A-3
MULTIPOINT FUEL INJECTION (MPI)13100010265
GENERAL INFORMATION
The Multipoint Fuel Injection System consists
of sensors which detect the engine conditions,
the engine-ECU which controls the system
based on signals from these sensors, and
actuators which operate under the control of
the engine-ECU. The engine-ECU carries outactivities such as fuel injection control, idle
speed control and ignition timing control. In
addition, the engine-ECU is equipped with
several diagnosis modes which simplify
troubleshooting when a problem develops.
FUEL INJECTION CONTROL
The injector drive times and injector timing are
controlled so that the optimum air/fuel mixture
is supplied to the engine to correspond to the
continually-changing engine operation condi-
tions.
A single injector is mounted at the intake port
of each cylinder. Fuel is sent under pressure
from the fuel tank by the fuel pump, with the
pressure being regulated by the fuel pressure
regulator. The fuel thus regulated is distributed
to each of the injectors.
Fuel injection is normally carried out once for
each 2-cylinder group for every two rotationsof the crankshaft. This is called group fuel
injection. The engine-ECU provides a richer
air/fuel mixture by carrying out ªopen-loopº
control when the engine is cold or operating
under high load conditions in order to maintain
engine performance. In addition, when the
engine is warm or operating under normal
conditions, the engine-ECU controls the air/fuel
mixture by using the oxygen sensor signal to
carry out ªclosed-loopº control in order to obtain
the theoretical air/fuel mixture ratio that
provides the maximum cleaning performance
from the three way catalyst.
IDLE AIR CONTROL
The idle speed is kept at the optimum speed
by controlling the amount of air that bypasses
the throttle valve in accordance with changes
in idling conditions and engine load during
idling. The engine-ECU drives the idle speed
control (ISC) motor to keep the engine running
at the pre-set idle target speed in accordance
with the engine coolant temperature and airconditioner load. In addition, when the air
conditioner switch is turned off and on while
the engine is idling, the ISC motor operates
to adjust the throttle valve bypass air amount
in accordance with the engine load conditions
in order to avoid fluctuations in the engine
speed.
IGNITION TIMING CONTROL
The power transistor located in the ignition
primary circuit turns ON and OFF to control
the primary current flow to the ignition coil. This
controls the ignition timing in order to provide
the optimum ignition timing with respect to theengine operating conditions. The ignition timing
is determined by the engine-ECU from the
engine speed, intake air volume, engine coolant
temperature and atmospheric pressure.
SELF-DIAGNOSIS FUNCTION

When an abnormality is detected in one
of the sensors or actuators related to
emission control, the engine warning lamp
(check engine lamp) illuminates as a
warning to the driver.

When an abnormality is detected in one
of the sensors or actuators, a diagnosiscode corresponding to the abnormality is
output.

The RAM data inside the ENGINE-ECU
that is related to the sensors and actuators
can be read by means of the MUT-II. In
addition, the actuators can be force-driven
under certain circumstances.

MPI ± Troubleshooting13A-9
Engine warning lamp inspection items
Engine-ECU
Oxygen sensor
Air flow sensor
Intake air temperature sensor
Throttle position sensor
Engine coolant temperature sensor
Crank angle sensor
Top dead centre sensor
Barometric pressure sensor
Ignition timing adjustment signal
Injector
Immobilizer system
Caution
Engine warning lamp will come on even when terminal
for ignition timing adjustment is short-circuited.
Therefore, it is not abnormal that the lamp comes
on even when terminal for ignition timing adjustment
is short-circuited at the time of ignition timing
adjustment.
METHOD OF READING AND ERASING DIAGNOSIS
CODES
Refer to GROUP 00 ± How to Use Troubleshooting/Inspection
Service Points.
INSPECTION USING MUT-II DATA LIST AND
ACTUATOR TESTING
1. Carry out inspection by means of the data list and the
actuator test function.
If there is an abnormality, check and repair the chassis
harnesses and components.
2. After repairing, re-check using the MUT-II and check that
the abnormal input and output have returned to normal
as a result of the repairs.
3. Erase the diagnosis code memory.
4. Remove the MUT-II.
5. Start the engine again and carry out a road test to confirm
that the problem has disappeared.

MPI ± Troubleshooting13A-11
INSPECTION PROCEDURE FOR DIAGNOSIS CODES
Code No. 11 Oxygen sensor systemProbable cause
Range of Check

3 minutes have passed after engine was started.

Engine coolant temperature is approx. 80C or more.

Intake air temperature is 20 ± 50C.

Engine speed is approx. 2,000 ± 3,000 r/min

Vehicle is moving at constant speed on a flat, level road surface
Set conditions

The oxygen sensor output voltage is around 0.6 V for 30 seconds (does not cross
0.6 V for 30 seconds).

When the range of check operations given above which accompany starting of
the engine are carried out four time in succession, a problem is detected after
each operation.
Malfunction of the oxygen sensor

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

Malfunction of the engine-ECU
Check the oxygen sensor. (Refer to P.13A-88.)NG
Replace
OK
Measure at the oxygen sensor connector B-03.

Disconnect the connector, and measure at the
harness side.
1. Voltage between 1 and earth (Ignition switch: ON)
OK:System voltage
2. Continuity between 2 and earth
OK:Continuity
OK1. NG
Check the harness wire between the
oxygen sensor and the control relay
connector, and repair if necessary.
2. NG
Check the following connector.
C-51, C-60NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between the
engine-ECU and the oxygen sensor
connector.NG
Repair
OK
Replace the engine-ECU.
Measure at the engine-ECU connector C-50.

Disconnect the connector, and measure at the
harness side.

Voltage between 35 and earth (Ignition switch: ON)
OK:System voltage
NGCheck the following connector.
B-03, C-60NG
Repair
OK
Check the following connectors.
B-03, C-50NG
RepairCheck trouble symptom.OK
OKNGCheck the harness wire between the
engine-ECU and the oxygen sensor
connector, and repair if necessary.
Check trouble symptom.
NG
Check the harness wire between the engine-ECU and
the oxygen sensor connector.NG
Repair
OK
Replace the engine-ECU.

MPI ± Troubleshooting13A-12
Code No. 12 Air flow sensor systemProbable cause
Range of Check

Engine speed is 500 r/min or more.
Set conditions

Sensor output frequency is 3 Hz or less for 4 seconds.
Malfunction of the air flow sensor

Improper connector contact, open circuit or
short-circuited harness wire of the air flow sensor

Malfunction of the engine-ECU
Measure at the air flow sensor con-
nector A-77.

Connect the connector. (Use
the test harness: MB991348)
1. Voltage between 3 and earth
(Engine: Idling)
OK:2.2 ± 3.2 V
2. Voltage between 7 and earth
OK:0 ± 1 V (Engine: idling)
6 ± 9 V (2,000 r/min)
OK
Replace the engine-ECU.1. NG
Check the air flow sensor circuit.
(Refer to P.13A-54, INSPECTION
PROCEDURE 45.)
2. NG
Measure at the engine-ECU con-
nector C-49.

Connect the connector.

Voltage between 19 and earth
(Ignition switch: ON)
OK:6±9 V
OK
Check the following connector.
C-49
OK
Check trouble symptom.
NG
Replace the engine-ECU.NG
Check the following connector.
A-77NG
Repair
OK
Check trouble symptom.
NG
NG
Repair
Replace the air flow sensor.
Code No. 13 Intake air temperature sensor systemProbable cause
Range of Check

Ignition switch: ON

Excluding 60 seconds after the ignition switch is turned to ON or immediately
after the engine starts.
Set conditions

Sensor output voltage is 4.6 V or more (corresponding to an intake air temperature
of ±45C or less) for 4 seconds.
or

Sensor output voltage is 0.2V or less (corresponding to an intake air temperature
of 125C or more) for 4 seconds.
Malfunction of the intake air temperature sensor

Improper connector contact, open circuit or
short-circuited harness wire of the intake air
temperature sensor circuit

Malfunction of the engine-ECU
Check the intake air temperature
sensor.
(Refer to P.13A-86.)NG
Replace
OK
Measure at the air flow sensor con-
nector A-77.

Disconnect the connector, and
measure at the harness side.

Voltage between 6 and earth
(Ignition switch: ON)
OK:4.5 ± 4.9 V

Continuity between 5 and earth
OK:ContinuityNGCheck the following connector.
C-51NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between
the engine-ECU and the intake air
temperature sensor connector.NG
Repair
OK
Replace the engine-ECU. OK
Check the following connector.
A-77NG
Repair
OK
Check trouble symptom.NGReplace the engine-ECU.

MPI ± Troubleshooting13A-13
Code No. 14 Throttle position sensor systemProbable cause
Range of Check

Ignition switch: ON

Excluding 60 seconds after the ignition switch is turned to ON or immediately
after the engine starts.
Set conditions

When the idle position switch is ON, the sensor output voltage is 2 V or more
for 4 seconds.
or

The sensor output voltage is 0.2 V or less for 4 seconds.
Malfunction of the throttle position sensor or
maladjustment

Improper connector contact, open circuit or
short-circuited harness wire of the throttle position
sensor circuit

Improper ªONº state of idle position switch

Short circuit of the idle position switch signal line

Malfunction of the engine-ECU
MUT-II Data list
26 Idle position switch system
OK:With the throttle valve at the
idle position: ON
With the throttle valve slight-
ly open: OFFNGCheck the idle position switch system.
(Refer to P.13A-40 INSPECTION
PROCEDURE 25.)
OK
Check the throttle position sensor.
(Refer to P.13A-87.)NG
Replace
OK
Measure at the throttle position sensor
connector A-47.

Disconnect the connector, and
measure at the harness side.

Voltage between 4 and earth
(Ignition switch: ON)
OK:4.8 ± 5.2 V

Continuity between 1 and earth
OK:ContinuityNGCheck the following connector.
C-51NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between the
engine-ECU and the throttle position
sensor connector.NG
Repair
OK
Replace the engine-ECU. OK
Check the throttle position sensor out-
put circuit. (Refer to P.13A-55, IN-
SPECTION PROCEDURE 46.)

MPI ± Troubleshooting13A-14
Code No. 21 Engine coolant temperature sensor systemProbable cause
Range of Check

Ignition switch: ON

Excluding 60 seconds after the ignition switch is turned to ON or immediately
after the engine starts.
Set conditions

Sensor output voltage is 4.6 V or more (corresponding to an engine coolant
temperature of ±45C or less) for 4 seconds.
or

Sensor output voltage is 0.1 V or less (corresponding to an engine coolant
temperature of 140C or more) for 4 seconds.
Malfunction of the engine coolant temperature sensor

Improper connector contact, open circuit or
short-circuited harness wire of the engine coolant
temperature sensor circuit

Malfunction of the engine-ECU
Range of Check

Ignition switch: ON

Engine speed is approx. 50 r/min or more
Set conditions

The sensor output voltage increases from 1.6 V or less (corresponding to an
engine coolant temperature of 40C or more) to 1.6 V or more (corresponding
to an engine coolant temperature of 40C or less).

After this, the sensor output voltage is 1.6 V or more for 5 minutes.
Check the engine coolant temperature
sensor. (Refer to P.13A-86.)NG
Replace
OK
Measure at the engine coolant temper-
ature sensor connector A-64.

Disconnect the connector, and
measure at the harness side.

Voltage between 1 and earth
(Ignition switch: ON)
OK:4.5 ± 4.9 V

Continuity between 2 and earth
OK:ContinuityNGCheck the following connector.
C-51NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between the
engine-ECU and the engine coolant
temperature sensor connector.NG
Repair
OK
Replace the engine-ECU.
Check the following connector.
A-64OKCheck trouble symptom.
NG
Replace the engine-ECU.NG
RepairOK

MPI ± Troubleshooting13A-15
Code No. 22 Crank angle sensor systemProbable cause
Range of Check

Engine is cranking.
Set conditions

Sensor output voltage does not change for 4 seconds (no pulse signal input.)
Malfunction of the crank angle sensor

Improper connector contact, open circuit or
short-circuited harness wire of the crank angle sensor

Malfunction of the engine-ECU
Measure at the distributor connector A-72.

Connect the connector. (Use the test harness: MB991348.)

Voltage between 2 and earth (Engine: cranking)
OK:0.4 ± 4.0 V

Voltage between 2 and earth (Engine: idling)
OK:1.5 ± 2.5 V
NGOKReplace the engine-ECU.
Measure at the distributor connector A-72.

Disconnect the connector, and measure at the harness side.
1. Voltage between 3 and earth (Ignition switch: ON)
OK:System voltage
2. Voltage between 2 and earth (Ignition switch: ON)
OK:4.8 ± 5.2 V
3. Continuity between 4 and earth
OK:Continuity
OK
Check the following con-
nector. A-72NG
Repair
OK
Check trouble symptom.
NG
Replace the distributor.1. NG
Check the harness wire between the crank angle sensor and the
control relay connector, and repair if necessary.
2. NGCheck the following con-
nector. C-51NG
Repair
OK3. NG
Check trouble symptom.
NG
Check the harness wire
between the engine-ECU and
the distributor connector.NG
Repair
OK
Replace the engine-ECU.
Check the harness wire between the crank angle sensor and the
earth, and repair if necessary.

MPI ± Troubleshooting13A-16
Code No. 23 Top dead centre sensor systemProbable cause
Range of Check

Ignition switch: ON

Engine speed is approx. 50 r/min or more.
Set conditions

Sensor output voltage does not change for 4 seconds (no pulse signal input.)
Malfunction of the camshaft position sensor

Improper connector contact, open circuit or
short-circuited harness wire of the top dead centre
sensor circuit

Malfunction of the engine-ECU
Measure at the distributor connector A-72.

Connect the connector. (Use the test harness: MB991348)

Voltage between 1 and earth (Engine: cranking)
OK:0.4 ± 3.0 V

Voltage between 1 and earth (Engine: idling)
OK:0.5 ± 2.0 VOKReplace the engine-ECU.
NG
Measure at the distributor connector A-72.

Disconnect the connector, and measure at the harness side.
1. Voltage between 3 and earth (Ignition switch: ON)
OK:System voltage
2. Voltage between 1 and earth (Ignition switch: ON)
OK:4.8 ± 5.2 V
3. Continuity between 4 and earth
OK:Continuity1. NGCheck the harness wire between the top dead centre sensor and
the control relay connector, and repair if necessary.
2. NGCheck the following con-
nector. C-51NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire
between the engine-ECU and
the distributor connector.NG
Repair
OK
Replace the engine-ECU. 3. NG
OK
Check the following con-
nector. A-72NG
Repair
OK
Check trouble symptom.
NG
Replace the distributor.
Check the harness wire between the top dead centre sensor and
the earth, and repair if necessary.