Mitsubishi Electric Lancer Evolution-VII Workshop Manual page 1259

13A-122
Wave Pattern Observation Points
Check that the standard wave pattern appears when the stepper motor is operating.
Point A: Presence or absence of induced electromotive force from the motor turning. (Refer to the abnormal
wave pattern.)
Contrast with standard wave pattern
Induced electromotive force does not appear or is extremely small.
Point B: Height of coil reverse electromotive force
Contrast with standard wave pattern
Coil reverse electromotive force does not appear or is extremely small.
Open
circuit
side
Normal
side
MPI -
Troubleshooting
Examples of Abnormal Wave Pattern
Example 1
D
Cause of problem
Motor is malfunctioning. (Motor is not operating.)
Wave pattern characteristics
Induced electromotive force from the motor turning does
not appear.
Example 2
D
Cause of problem
Open circuit in the line between the stepper motor and
the engine-ECU.
Wave pattern characteristics
Current is not supplied to the motor coil on the open
circuit side. (Voltage does not drop to 0 V.)
Furthermore, the induced electromotive force waveform
at the normal side is slightly different from the normal
waveform.
Probable cause
Motor is malfunctioning
Probable cause
Short in the coil