Oscilloscope Patterns and Waveforms

IDLE AIR CONTROL MOTOR (STEPPER MOTOR)

Required Special Tool:
MD998463: Test Harness




Measurement Method
1. Disconnect the idle air control motor connector, and connect the test harness special tool (MD998463) in between.
2. Connect the oscilloscope probe to the idle air control motor 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 oscilloscope probe to PCM terminals 14, 15, 28 and 29.

Standard Wave Pattern Part 1:

Standard Wave Pattern Part 2:

Wave Pattern Observation Points
1. Check that the standard wave pattern appears when the idle air control motor is operating.




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




Point B: Height of coil back electromotive force

Examples of Abnormal Wave Patterns




Example 1

Cause of problem
- Malfunction of motor. (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 idle air control motor and the PCM.

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 wave pattern at the normal side is slightly different from the normal wave pattern.