ECU MITSUBISHI LANCER EVOLUTION VI 1999 Owner's Guide

MPI – Troubleshooting13-35
INSPECTION PROCEDURE 23
Low alternator output voltage (approx. 12.3 V)
Probable cause
The alternator may be defective, or malfunctions, which are listed in the right column,
may be suspected.
Malfunction of charging system

Short circuit in harness between alternator G terminal
and engine-ECU

Malfunction of engine-ECU
Measure at the alternator connector
side. A-05

Connect the connector.
(Test harness: MB991519)

Voltage between 1 (black clip) and
earth
Engine: at idle
Radiator fan: does not run
Headlamp: OFF → ON
Brake lamp: OFF → ON
Rear defogger switch:
OFF → ON
OK:Voltages rises
by 0.2 – 3.5 V.NGMeasure at the alternator connector.
A-05

Disconnect the connector, and
measure at the harness side.

Disconnect the engine-ECU con-
nector.

Continuity between 1 and earth
OK:No continuityNGCheck the harness wire between the
alternator and the engine-ECU connec-
tor, and repair if necessary.
OK
Check the alternator.
OK
Check the harness wire between the
alternator and the engine-ECU connec-
tor.NG
Repair
OK
Replace the engine-ECU.
INSPECTION PROCEDURE 24
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 system 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 or short-circuited
harness wire

Disconnected engine-ECU earth wire

Malfunction of the engine-ECU
Check the control relay. (Refer to P.13-68.)NG
Replace
OK
Measure at the control relay connector B-27.

Disconnect the connector, and measure at the harness side.

Voltage between 3, 4 and earth
OK:System voltageNGCheck the following
connector: A-28NG
Repair
OK
Check trouble symptom.
NG
Check 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.13-53, INSPECTION PROCEDURE 45.)

MPI – Troubleshooting13-36
INSPECTION PROCEDURE 25
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 or short-circuited
harness wire

Malfunction of the engine-ECU
OK
Check the harness wire between resistor connector and fuel pump
drive terminal and between fuel pump relay No.2 connector and
fuel pump drive terminal, and repair if necessary.
OK
Check the resistor. (Refer to P.13-34.)*NG
Replace
OK
Measure at the resistor connector A-124.

Disconnect the connector.

Voltage between 1 and earth

MUT-II Actuator test: Fuel pump relay No.2 drive
OK:System voltageNGCheck the harness wire between fuel pump relay No.2 and resistor
connector, and repair if necessary.
OK
Measure at the engine-ECU connector B-60.

Connect the connector.

Voltage between 39 and earth

MUT-II Actuator test: Fuel pump drive
OK:System voltageNGCheck the harness wire between fuel pump relay No.2 and
engine-ECU connector, and repair if necessary. NG
Check the harness wire between fuel pump relay and fuel pump
relay No.2 connector, and repair if necessary.
OK
Measure at the fuel pump relay No.2 connector A-123.

Disconnect the connector.

Voltage between each of 3 and 5 and earth

MUT-II Actuator test: Fuel pump drive
OK:System voltage
OK
Check the fuel pump relay No.2. (Refer to P.13-68)NG
Replace
OK
Check the following connectors:
D-18, D-04, B-64, A-124, A-123, B-59, B-60NG
Repair
OK
Measure at the fuel pump relay connector B-28.

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.13-54, INSPECTION PROCEDURE 47.)
OK
Check the fuel pump relay. (Refer to P.13-68.)NG
Replace
Check the fuel pump operation by applying the system voltage
to the fuel pump drive terminal.NGCheck the fuel pump circuit.
(Refer to P.13-53, INSPECTION PROCEDURE 46.)
NOTE
*: Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).

MPI – Troubleshooting13-37
INSPECTION PROCEDURE 25
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.

The engine-ECU supplies power to the fuel pump through the resistor at low load
operations. It supplies power directly to the fuel pump at high load operations
to increase the pump output.
Malfunction of the fuel pump relay

Malfunction of the fuel pump relay No.2

Malfunction of the fuel pump

Malfunction of fuel pump resistor

Improper connector contact, open or short-circuited
harness wire

Malfunction of engine-ECU
OK
Check the fuel pump drive control circuit.
(Refer to P.13-54, INSPECTION PROCEDURE 47.)
Check the harness wire between fuel pump
relay No.2 and fuel pump relay connector,
and repair if necessary.NG
Repair
NG
OK
Check trouble symptom.
NG
Check the harness wire between fuel pump relay No.2 and
engine-ECU connector, and repair if necessary.
OK
Check trouble symptom.
NG
Replace the engine-ECU.
OK
Check trouble symptom.
OK
Check the following connector: B-60NG
Repair
OK
Measure at the engine-ECU connector B-60.

Disconnect the connector, and measure at the harness side.

Voltage between 39 and earth

MUT-II Actuator test: 07 Fuel pump
OK:System voltageNGCheck the following connector: A-123NG
Repair NG
Check the harness wire between fuel pump resistor and fuel pump
relay connector, and repair if necessary.
OK
Measure at the fuel pump resistor connector A-124.

Disconnect the connector, and measure at the harness side.

Voltage between 1 and earth

MUT-II Actuator test: 13 Fuel pump relay No.2
OK:System voltage
OK
Measure at the fuel pump relay No.2 connector A-123.

Disconnect the connector, and measure at the harness side.

Disconnect the fuel pump resistor connector.

Voltage between each of 1 and 3 and earth

MUT-II Actuator test: 07 Fuel pump drive
OK:System voltageNGCheck the following connector: B-28NG
Repair
OK
Check the fuel pump relay No.2 and fuel pump resistor.
(Refer to P.13-68.)NG
Replace
OK
Check the fuel pump relay. (Refer to P.13-68.)NG
Replace
Check the harness wire between fuel pump resistor and fuel pump
connector, and repair if necessary.
OK
Perform fuel pump operation check.

Disconnect the fuel pump resistor connector.

Apply system voltage to terminal No.2 of the harness side
connector.
OK:Fuel pump operates.NG
Perform fuel pump operation check.

Disconnect the fuel pump relay No.2 connector.

Apply system voltage to terminal No.2 of the harness side
connector.
OK:Fuel pump operates.NGCheck the fuel pump circuit.
(Refer to P.13-54, INSPECTION PROCEDURE 46.)

MPI – Troubleshooting13-38
INSPECTION PROCEDURE 26
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 cable

Maladjustment of the fixed SAS

Maladjustment of the idle position switch and throttle
position sensor

Improper connector contact, open or short-circuited
harness wire

Malfunction of the engine-ECU
Check the idle position switch. (Refer to P.13-30.)*NGReplace the throttle position sensor.
OK
Measure at the throttle position sensor connector A-16.

Disconnect the connector, and measure at the harness side.

Voltage between 3 and earth (Ignition switch: ON)
OK:4 V or higher

Continuity between 4 and earth
OK:ContinuityNGCheck the following
connector: B-62NG
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-16NG
Repair
OK
Check trouble symptom.
NG
Replace the engine-ECU.
NOTE
*: Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).
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 or short-circuited
harness wire

Malfunction of the engine-ECU
Measure at the engine-ECU connector B-62.

Disconnect the connector, and measure at the harness side.
1. Voltage between 71 and earth (Ignition switch: START)
OK:8V
2. Continuity between 91 and earth
OK:Continuity1. NGCheck the following
connector: B-64NG
Repair
OK
Check trouble symptom.
NG
Check harness wire be-
tween the engine-ECU
and ignition switch con-
nector.NG
Repair
OK
Check the ignition switch.
2. NG
Check the harness wire between engine-ECU connector (terminal
No.91) and earth, and repair if necessary.
OK
Check the following
connector: B-62NG
Repair
OK
Check trouble symptom.
NG
Replace the engine-ECU.

MPI – Troubleshooting13-39
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 or short-circuited
harness wire

Malfunction of the engine-ECU
Check the power steering fluid pressure switch.NG
Replace
OK
Measure at the power steering fluid pressure switch connector
A-101.

Disconnect the connector, and measure at the harness side.

Voltage between 1 and earth (Ignition switch: ON)
OK:System voltageNGCheck the following
connectors: A-28, B-60NG
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-101NG
Repair
OK
Check trouble symptom.
NG
Replace the engine-ECU.
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 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-59, B-60.

Disconnect the connector, and measure at the harness side.

Voltage between 22 and earth, and 45 and earth
(Ignition switch: ON, A/C switch: ON)
OK:System voltage

Short-circuit between 22 and earth
(Ignition switch: ON, A/C switch: ON)
OK:A/C compressor clutch turns on.NGCheck the A/C system. (Refer to GROUP 55 – On-vehicle Service.)
OKCheck the following
connectors: B-59, B-60NG
Replace
OK
Check trouble symptom.
NG
Replace the engine-ECU.

MPI – Troubleshooting13-40
INSPECTION PROCEDURE 30
Fan motor relay system (Radiator fan, A/C condenser fan)
Probable cause
The engine-ECU turns on/off the built-in power transistor to control the fan motor
relay.
Malfunction of the fan motor relay

Malfunction of the fan motor

Improper connector contact, open or short-circuited
harness wire

Malfunction of engine-ECU
NG

Check the radiator fan circuit.

Check the A/C condenser fan circuit.
(Refer to Electrical Wirings.)
NG
Replace the engine-ECU.
OK
Check trouble symptom.
Measure at the engine-ECU connector B-59.

Disconnect the connector, and measure at the harness side.

Voltage between each of 20 and 21 and earth
(Ignition switch: ON)
OK:System voltage

Short the terminal 21 to earth.
(Ignition switch: ON)
OK:Fan operates at low speed.

Short the terminals 20 and 21 to earth.
(Ignition switch: ON)
OK:Fan operates at high speed.OKCheck the following connector: B-59NG
Repair

MPI – Troubleshooting13-41
INSPECTION PROCEDURE 30
Fan motor relay system (Radiator fan, A/C condenser fan)
Probable cause
The engine-ECU turns on/off the built-in power transistor to control the fan motor
relay.
Malfunction of the fan motor relay

Malfunction of the fan motor

Malfunction of thermostat

Improper connector contact, open or short-circuited
harness wire

Malfunction of engine-ECU
NG
Check the engine coolant temperature sensor. (Refer to P.13-10,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE 21.)
OK
Replace the engine-ECU.
NG
MUT-II Data list
21 Engine coolant temperature sensor
OK:The engine coolant temperature agrees with the reading
of MUT-II when measured with the engine idling in warm
condition.OKCheck the thermostat.NG
Replace
OK
Check trouble symptom.
OK
Check the following connector: B-60NG
Repair NG
Check the A/C condenser fan circuit. (Refer to Electrical Wirings.)
NG
Measure at the engine-ECU connector B-60.

Disconnect the connector, and measure at the harness side.

Check the A/C condenser fan for operating condition.
(Ignition switch: ON)
OK:A/C condenser fan is stationary.

Voltage between each of 32 and 34 and earth
(Ignition switch: ON)
OK:System voltage

Short the terminal 32 to earth. (Ignition switch: ON)
OK:A/C condenser fan operates at high speed.

Short the terminal 34 to earth. (Ignition switch: ON)
OK:A/C condenser fan operates at low speed.
Check trouble symptom.
OK
OK
Check the following connector: B-59NG
Repair
Measure at the engine-ECU connector B-59.

Disconnect the connector, and measure at the harness side.

Check the radiator fan for operating condition.
(Ignition switch: ON)
OK:Radiator fan is stationary.

Voltage between each of 20 and 21 and earth
(Ignition switch: ON)
OK:System voltage

Short the terminal 20 to earth.
(Ignition switch: ON)
OK:Radiator fan operates at high speed.

Short the terminal 21 to earth.
(Ignition switch: ON)
OK:Radiator fan operates at low speed.NGCheck the radiator fan circuit. (Refer to Electrical Wirings.)

MPI – Troubleshooting13-42
INSPECTION PROCEDURE 31
Oxygen sensor system
Probable cause
When CO or HC concentration is too high, the malfunction of the parts shown at
right may be the cause.

The oxygen sensor detects the density of oxygen in exhaust gas and inputs it
to the engine-ECU after converting into a voltage signal.

The engine-ECU controls the fuel injection amount based on this signal such that
the stoichiometric air/fuel mixture ratio can be obtained.
Malfunction of oxygen sensor

Improper connector contact, open or short-circuited
harness wire

Malfunction of engine-ECU
OK
Replace the engine-ECU.
Check the harness wire between
engine-ECU and oxygen sensor connector.NG
Repair
NG
OK
Check trouble symptom.
OK
Replace the engine-ECU.
NG
Check the harness wire between
engine-ECU and oxygen sensor connector.NG
Repair
OK
Check trouble symptom.
OK
Check the following connector: A-63NG
Repair
OK
Measure at the oxygen sensor connector A-63.

Disconnect the connector, and measure at the harness side.

Continuity between 2 and earth
OK:ContinuityNGCheck the following connector: B-62NG
Repair
Check the oxygen sensor. (Refer to P.13-32.)*NG
Replace
NOTE
*: Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).

MPI – Troubleshooting13-43
INSPECTION PROCEDURE 31
Oxygen sensor system
Probable cause
When CO or HC concentration is too high, the malfunction of the parts shown at
right may be the cause.

The oxygen sensor detects the density of oxygen in exhaust gas and inputs it
to the engine-ECU after converting into a voltage signal.

The engine-ECU controls the fuel injection amount based on this signal such that
the stoichiometric air/fuel mixture ratio can be obtained.
Malfunction of oxygen sensor

Improper connector contact, open or short-circuited
harness wire

Malfunction of engine-ECU
OK
Replace the engine-ECU.
NG
Check the harness wire between oxygen sensor, engine-ECU,
and repair if necessary.
OK
Check trouble symptom.
NG
Check the harness wire between oxygen sensor and engine-ECU,
and repair if necessary.
OK
Check trouble symptom.
OK
Check trouble symptom.NGCheck the harness wire between
engine-ECU and oxygen sensor.NG
Repair
OK
Check the following connector: B-61NG
Repair
OK
NG
Measure at the engine-ECU connector B-61.

Disconnect the connector, and measure at the harness side.

Voltage between 60 and earth
(Ignition switch: ON)
OK:System voltageCheck the following connector: A-63NG
Repair 1. NG
Check the harness wire between oxygen sensor and control relay,
and repair if necessary.
OK
2. NG
Measure at the oxygen sensor connector A-63.

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
Check the following connector: B-62NG
Repair
Check the oxygen sensor. (Refer to P.13-32)*NG
Replace
NOTE
*: Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).

MPI – Troubleshooting13-44
INSPECTION PROCEDURE 32
Ignition circuit system
Probable cause
The engine-ECU interrupts the ignition coil primary current by turning the power transistor
inside the engine-ECU ON and OFF.
Malfunction of ignition switch.

Improper connector contact, open or short-circuited
harness wire

Malfunction of the engine-ECU
Measure at the ignition coil connectors A-110, A-111.

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:Continuity1. NGCheck the following
connectors: B-65, B-76NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire
between ignition coil and
ignition switch connector.NG
Repair
OK
Check the ignition switch. 2. NG
Check the harness wire between ignition coil connector and earth,
and repair if necessary.
OK
Check the following
connectors:
A-110, A-111NG
Repair
OK
Check trouble symptom.NGCheck ignition coil and power transistor unit system. (Refer to
P.13-16, INSPECTION PROCEDURE FOR DIAGNOSIS CODE
44.)
INSPECTION PROCEDURE 33
Idle speed control (ISC) servo (Stepper motor) system
Probable cause
The engine-ECU controls the intake air volume during idling by opening and closing
the servo valve located in the bypass air passage.
Malfunction of ISC servo

Improper connector contact, open or short-circuited
harness wire

Malfunction of the engine-ECU
Check the ISC servo.NG
Replace
OK
Measure at the ISC servo connector A-18.

Disconnect the connector and measure at the harness side.

Voltage between 2 and earth, and 5 and earth (Ignition switch:
ON)
OK:System voltageNGCheck the harness wire between control relay and ISC servo con-
nector, and repair if necessary.
OK
Measure at the engine-ECU connector B-59.

Disconnect the connector, measure at the harness side.

Voltage between each of 4, 5, 17, 18 and earth (Ignition switch:
ON)
OK:System voltageNGCheck the following
connector: A-18NG
Repair
OK
Check trouble symptom.
NG
Check harness wire between engine-ECU and ISC servo connector,
and repair if necessary.
OK
Check the following
connector: B-59NG
Repair
OK
Check trouble symptom.NGReplace the engine-ECU.