Oscilloscope Check

IDLE AIR CONTROL (STEPPER) MOTOR





Measurement Method
1. Disconnect the IAC motor connector, and connect the special tool (test harness: MD998463) in between.
2. Connect the analyzer special patterns pickup to the IAC motor-side connector terminal 1 (red clip of special tool), terminal 3 (blue clip), terminal 4 (black clip) and terminal 6 (yellow clip) respectively.

Alternate Method Test harness not available)
1. Connect the analyzer special patterns pickup to ECM terminal 4, connection terminal 5, connection terminal 17, and connection terminal 18 respectively.

Standard Wave Pattern




Observation conditions

Standard wave pattern

Wave Pattern Observation Points
Check that the standard wave pattern appears when the IAC motor is operating.




Point A: Presence or absence of induced electromotive force from the motor turning. (Refer to the abnormal wave pattern.)




Point B: Height of coil reverse electromotive force

Examples of Abnormal Wave Pattern





- Example 1

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

Cause of problem
Open circuit in the line between the IAC motor and the ECM.

Wave pattern characteristics
Current is not supplied to the motor coil on the open circuit side. (Voltage does not drop to 0 Volt.) Furthermore the induced electromotive force waveform at the normal side is slightly different from the normal waveform.