IDLE SPEED CONTROL SERVO (STEPPER MOTOR) CHECK

Check that the engine coolant temperature is 20°C or below.

NOTE: Disconnecting the engine coolant temperature sensor connector and connecting the harness-side of the connector to another engine coolant temperature sensor that is at 20°C or below is also okay.

Check that the operation sound of the stepper motor can be heard after the ignition is switched "ON" position (but without starting the motor).

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 of the engine control unit.

Check the Coil resistance

Disconnect the idle speed control servo connector.

Measure the resistance between terminal No. 2 and either terminal No. 1 or terminal No. 3 of the connector at the idle speed control servo side.

Standard value: 26 - 33 Ω (at 20°C)

Measure the resistance between terminal No. 5 and either terminal No. 6 or terminal No. 4 of the connector at the idle speed control servo side.

Standard value: 26 - 33 Ω (at 20°C)

Operation Check

Remove the throttle body.

Remove the stepper motor.

Connect the special tool Test harness (MB991709) to the idle speed control servo connector.

Connect the positive (+) terminal of a power supply (approximately 6 V) to the terminals No. 2 and No. 5.

With the idle speed control servo as shown in the illustration, connect the negative (-) terminal of the power supply to each clip as described in the following steps, and check whether or not a vibrating feeling (a feeling of very slight vibration of the stepper motor) is generated as a result of the activation of the stepper motor.

Connect the negative (-) terminal of the power supply to the red and black clip.

Connect the negative (-) terminal of the power supply to the blue and black clip.

Connect the negative (-) terminal of the power supply to the blue and yellow clip.

Connect the negative (-) terminal of the power supply to the red and yellow clip.

Connect the negative (-) terminal of the power supply to the red and black clip.

Repeat the tests in sequence from (5) to (1).

If, as a result of these tests, vibration is detected, the stepper motor can be considered to be normal.


	IDLE SPEED CONTROL SERVO (STEPPER MOTOR) CHECK
	Check the Operation Sound
	Check that the engine coolant temperature is 20°C or below. NOTE: Disconnecting the engine coolant temperature sensor connector and connecting the harness-side of the connector to another engine coolant temperature sensor that is at 20°C or below is also okay. Check that the operation sound of the stepper motor can be heard after the ignition is switched "ON" position (but without starting the motor). 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 of the engine control unit.
	Check the Coil resistance
	Disconnect the idle speed control servo connector. Measure the resistance between terminal No. 2 and either terminal No. 1 or terminal No. 3 of the connector at the idle speed control servo side. Standard value: 26 - 33 Ω (at 20°C) Measure the resistance between terminal No. 5 and either terminal No. 6 or terminal No. 4 of the connector at the idle speed control servo side. Standard value: 26 - 33 Ω (at 20°C)
	Operation Check
	Remove the throttle body. Remove the stepper motor. Connect the special tool Test harness (MB991709) to the idle speed control servo connector. Connect the positive (+) terminal of a power supply (approximately 6 V) to the terminals No. 2 and No. 5. With the idle speed control servo as shown in the illustration, connect the negative (-) terminal of the power supply to each clip as described in the following steps, and check whether or not a vibrating feeling (a feeling of very slight vibration of the stepper motor) is generated as a result of the activation of the stepper motor. Connect the negative (-) terminal of the power supply to the red and black clip. Connect the negative (-) terminal of the power supply to the blue and black clip. Connect the negative (-) terminal of the power supply to the blue and yellow clip. Connect the negative (-) terminal of the power supply to the red and yellow clip. Connect the negative (-) terminal of the power supply to the red and black clip. Repeat the tests in sequence from (5) to (1). If, as a result of these tests, vibration is detected, the stepper motor can be considered to be normal.