Idle Air Control Motor (Stepper Motor) Check
IDLE AIR CONTROL MOTOR (STEPPER MOTOR) CHECKRequired Special Tool:
- MB991709: Test Harness Set
Checking the Operation Sound
1. Check that the engine coolant temperature is 20 degrees C (68 degrees F) or below.
NOTE: If necessary, you can disconnect the engine coolant temperature sensor connector and connect the harness-side of the connector to another engine coolant temperature sensor that is at 20 degrees C (68 degrees F) or below.
2. Check that the operation sound of the stepper motor can be heard after the ignition is switched ON (but do not start the engine).
3. If the operation sound cannot be heard, check the stepper motor's activation circuit. If the circuit is normal, it is probable that there is a malfunction of the stepper motor or engine control module (ECM).
Checking the Coil Resistance
1. Disconnect the idle air control motor connector.
2. Measure resistance between terminal No.2 and either terminal No.1 or terminal No.3 of the connector at the idle air control motor side.
Standard value: 28 - 33 Ohms [at 20 degrees C (68 degrees F)]
3. If resistance is not within the standard value, replace the IAC motor.
4. Measure the resistance between terminal No.5 and either terminal No.6 or terminal No.4 of the connector at the idle air control motor side.
Standard value: 28 - 33 Ohms [at 20 degrees C (68 degrees F)]
5. If resistance is not within the standard value, replace the IAC motor.
1. Remove the throttle body.
2. Remove the idle air control motor.
3. Connect special tool MB991709 to the idle air control motor connector.
4. Connect the positive battery terminal of a power supply (approximately 6 volts) to terminal No.2 and the terminal No.5.
5. Connect the negative battery terminal of the power supply to each clip as described in the following steps. Then check whether or not the stepper motor vibrates slightly as it operates.
1. Connect the negative terminal of the power supply to terminal No.1 and terminal No.4.
2. Connect the negative terminal of the power supply to terminal No.3 and terminal No.4.
3. Connect the negative terminal of the power supply to terminal No.3 and terminal No.6.
4. Connect the negative terminal of the power supply to terminal No.1 and terminal No.6.
5. Connect the negative terminal of the power supply to terminal No.1 and terminal No.4.
6. Repeat the tests in sequence from (5) to (1) to test opposite movement of the IAC.
6. If vibration is detected during the test, the stepper motor can be considered to be normal.