Mitsubishi Space Star. Manual - part 68

MPI  – 

Troubleshooting

13B-59

INSPECTION PROCEDURE 24

Check the engine-ECU power supply and earth circuit.

Measure the engine-ECU connectors, B-28, B-29, B-31.



Disconnect the connector and measure at the harness side

(1) Voltage between 82 and earth (Ignition switch: ON)

OK: System voltage

(2) Voltage between 38 and earth

OK: System voltage

(3) Voltage between 12, 25 and earth (Ignition switch: ON)

OK: System voltage (when the terminal 38 is earthed)

(4) Continuity between 13, 26 and earth

OK: Continuity

(5) Voltage between 80 and earth

OK: System voltage

(1) NG

Check the following
connectors: B-18, B-58

NG

Repair

OK

Check trouble symptom.

OK

Check the harness wire
between engine-ECU
and ignition switch con-
nector.

NG

Repair

OK

Check the ignition switch. 
(Refer to GROUP 54 – Ignition Switch and Immobilizer System.)

(2, 3) NG

Check the following
connector: B-26

NG

Repair

OK

Check trouble symptoms.

NG

Check the harness wire between engine-ECU and control relay
connector, and repair if necessary.

(4) NG

Check the harness wire between engine-ECU and earth, and
repair if necessary.

(5) NG

OK

Check the following
connectors:
B-28, B-29, B-31

NG

Repair

OK

Check trouble symptom.

NG

Replace the engine-ECU.

Check the following connectors:
B-18, B-45

NG

Repair

OK

Check trouble symptom.

NG

Check the harness wire between engine-ECU and battery, and
repair if necessary.

INSPECTION PROCEDURE 25

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.13B-71*.)

NG

Replace

OK

Measure at the control relay connector B-26.



Disconnect the connector, and measure at the harness side.



Voltage between 3, 4 and earth
OK: System voltage

NG

Check the following
connector: A-23

NG

Repair

OK

Check trouble symptom.

NG

Check the harness wire between battery and control relay connec-
tor, and repair if necessary.

OK

Check the engine-ECU power supply and earth circuit. 
(Refer to P.13B-59, INSPECTION PROCEDURE 24.)

NOTE:
*:

Refer to the ’99 SPACE STAR Workshop Manual (Pub. No. CMXE99E1)

MPI  – 

Troubleshooting

13B-60

INSPECTION PROCEDURE 26

Fuel pump system

Probable cause

The engine-ECU turns the fuel pump 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

OK

OK

Check trouble symptom.

NG

Check the harness wire between the
fuel pump and earth, and repair if nec-
essary.

OK

Check trouble symptom.

NG

Check the harness wire between the
fuel pump relay and ignition switch con-
nector.

NG

Repair

OK

Check the ignition switch. 
(Refer to GROUP 54 – Ignition Switch
and Immobilizer System.)

OK

Check trouble symptom.

OK

Check the fuel pump relay. 
(Refer to P.13B-71*.)

NG

Replace

OK

Check the harness wire between fuel
pump relay connector and fuel pump,
and repair if necessary.

Check the fuel pump operation. 
(Refer to P.13B-69*.)

NG

Measure at the fuel pump connector
D-13.



Disconnect the connector, and
measure at the harness side.



Continuity between 4 and earth
OK: Continuity

NG

Check the following connectors:
D-13, D-15

NG

Repair

OK

Check the following connectors:
B-18, B-27, D-13, D-15

NG

Check the harness wire between the
fuel pump relay and fuel pump connec-
tor.

NG

Repair

OK

Replace the fuel pump.

Measure at the fuel pump relay connec-
tor B-27.



Connect the connector.



Voltage between 1 and earth



MUT-

II

 Actuator test: Fuel pump

drive
OK: System voltage

NG

Measure at the fuel pump relay connec-
tor B-27.



Disconnect the connector, and
measure at the harness side.



Voltage between 4 and earth
(Ignition switch: ON)
OK: System voltage

NG

Check the following connectors:
B-18, B-58

NG

Repair

OK

Check trouble symptom.

OK

Check the following connector: B-27

NG

Repair

NG

Check the harness wire between the
engine-ECU and the fuel pump relay,
and repair if necessary.

NG

OK

Check the following connector: B-28

Repair

OK

Check trouble symptom.

NG

Replace the engine-ECU.

Measure at the engine-ECU connector
B-28.



Disconnect the connector, and
measure at the harness side.



Voltage between 22 and earth
(Ignition switch: ON)
OK: System voltage

NG

NG

Repair

NOTE:
*:

Refer to the ’99 SPACE STAR Workshop Manual (Pub. No. CMXE99E1)

MPI  – 

Troubleshooting

13B-61

INSPECTION PROCEDURE 27

Ignition switch-ST system

Probable cause

The ignition switch-ST inputs a HIGH signal to the engine-ECU while the engine
is cranking.
The engine-ECU controls fuel injection, etc. during starting based on this input.



Malfunction of ignition switch



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



Malfunction of the engine-ECU

Measure at the engine-ECU connector B-31.



Disconnect the connector, and measure at the harness side.



Voltage between 71 and earth (Ignition switch: START)
OK: 8V or more

NG

Check the following con-
nectors: A-74, B-18, B-58

NG

Repair

OK

Check trouble symptom.

NG

Check harness wire be-
tween the engine-ECU and
ignition switch connector.

NG

Repair

OK

Check the ignition switch. 
(Refer to GROUP 54 – Ignition Switch and Immobilizer system.)

OK

Check the following
connector: B-31

NG

Repair

OK

Check trouble symptom.

NG

Replace the engine-ECU.

INSPECTION PROCEDURE 28

Power steering fluid pressure switch system

Probable cause

The presence or absence of power steering load is input to the engine-ECU.
The engine-ECU controls the idle speed control (ISC) servo based on this input.



Malfunction of power steering fluid pressure switch



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



Malfunction of the engine-ECU

Check the power steering fluid pressure switch. 
(Refer to GROUP 37A – On-vehicle Service.)

NG

Replace

OK

Measure at the power steering fluid pressure switch connector
A-38.



Disconnect the connector, and measure at the harness side.



Voltage between 1 and earth (Ignition switch: ON)
OK: System voltage

NG

Check the following
connectors: A-23, B-29

NG

Repair

OK

Check trouble symptom.

NG

Check harness wire be-
tween engine-ECU and
power steering fluid pres-
sure switch connector.

NG

Repair

OK

Replace the engine-ECU.

OK

Check the following
connector: A-38

NG

Repair

OK

Check trouble symptom.

NG

Replace the engine-ECU.

MPI  – 

Troubleshooting

13B-62

INSPECTION PROCEDURE 29

A/C switch and A/C relay system

Probable cause

When an A/C ON signal is input to the engine-ECU, the engine-ECU carries out
control of the idle speed control (ISC) servo, and also operates the A/C compressor
magnetic clutch.



Malfunction of A/C control system



Malfunction of A/C switch



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



Malfunction of the engine-ECU

Check the A/C compressor relay. 
(Refer to GROUP 55 – On-vehicle Service.)

NG

Replace

OK

Measure at the engine-ECU connectors B-28, B-29.



Disconnect the connectors, and measure at the harness side.



Voltage between 8 and earth, and 45 and earth
(Ignition switch: ON, A/C switch: ON)
OK: System voltage



Short circuit between 8 and earth
(Ignition switch: ON, A/C switch: ON)
OK: A/C compressor clutch turns on.

NG

Check the A/C system. (Refer to GROUP 55 – On-vehicle Service.)

OK

Check the following
connectors: B-28, B-29

NG

Replace

OK

Check trouble symptom.

NG

Replace the engine-ECU.

INSPECTION PROCEDURE 30

Electrical load switch

Probable cause

During idling, the ON/OFF condition of switches is equipment which have a large
electrical load is input to the engine-ECU.
The engine-ECU controls the idle speed control servo on this input.



Improper connector contact, open circuit or
short-circuited harness wire in the headlamp relay
circuit



Improper connector contact, open circuit or
short-circuited harness wire in the defogger relay
circuit.



Malfunction of the engine-ECU

Measure at the engine-ECU connector B-29.



Disconnect the connectors, and measure at the harness side.



Voltage between 41 and earth
(Lighting switch: ON)
OK: System voltage

NG

Check the headlamp relay circuit. 
(Refer to ELECTRICAL WIRING.)
Check the defogger relay circuit. 
(Refer to ELECTRICAL WIRING.)

OK

Check the trouble symptoms.

OK

Check the following connector: B-29

NG

Repair

NG

Replace the engine-ECU.