Oscilloscope Testing

INSPECTION PROCEDURE USING AN ANALYZER

IDLE AIR CONTROL MOTOR (STEPPER MOTOR)

Measurement Method

1. Disconnect the idle air control motor connector, and connect the special tool (test harness: MB998463) in between.




2. Connect the analyzer special patterns pickup to the idle air control motor connector terminal 1 (red clip of the special tool), terminal 3 (green 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 terminals 14, 15, 25, and 29.(signal wave pattern.)




Observation conditions




Standard wave pattern

WAVE PATTERN OBSERVATION POINTS

Check that the standard wave pattern appears when the idle air control motor is operating.




Point A: Condition of wave pattern build-up section and maximum voltage (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 ECM.

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