Mitsubishi Lancer Evolution VI - Low Alternator Output Voltage (Approx. 12.3 V)

MPI – Troubleshooting
13-35
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.
D Malfunction of charging system
D Short circuit in harness between alternator G terminal
and engine-ECU
D Malfunction of engine-ECU
Measure at the alternator connector
side. A-05
D Connect the connector.
(Test harness: MB991519)
D 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.
NG
Measure at the alternator connector.
A-05
D Disconnect the connector, and
measure at the harness side.
D Disconnect the engine-ECU con-
nector.
D Continuity between 1 and earth
OK: No continuity
NG
Check 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.
D Malfunction of the ignition switch
D Malfunction of the control relay
D Improper connector contact, open or short-circuited
harness wire
D Disconnected engine-ECU earth wire
D 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.
D Disconnect the connector, and measure at the harness side.
D Voltage between 3, 4 and earth
OK: System voltage
NG
Check the following
connector: A-28
NG
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.)