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Idle Air Control Motor (Stepper Motor) - Federal





CIRCUIT DIAGRAM





INSPECTION USING SCAN TOOL








HARNESS INSPECTION PROCEDURE

USING OSCILLOSCOPE





1. Connect the probe to each oscilloscope pick-up point as shown in the circuit diagram.
2. Start the engine.
3. When the air conditioning switch is turned on, the idling speed increases to operate the idle air control. Check the instantaneous waveform.

COMPONENT TEST PROCEDURE

Checking The Operating Sound





1. Check that when the ignition switch is placed in the ON position (the engine not started) , the operating sound of the stepper motor can be heard over the idle control motor.
2. If no operating sound can be heard, check the stepper motor drive circuit. (If the circuit is good, a defective stepper motor or engine control module is suspected.)

Checking The Coil Resistance
1. Disconnect the idle control motor connector and connect the special tool (test harness).





2. Measure the resistance between terminal 2 (white clip of the special tool) of the connector at the idle control motor side and terminal 1 (red clip) or terminal 3 (blue clip).

Standard value: 28 - 33 Ohms [at 20°C (68°F)]

3. Measure the resistance between terminal 5 (green clip of the special tool) of the connector at the idle control motor side and terminal 6 (yellow clip) or terminal 4 (black clip).

Standard value: 28 - 33 Ohms [at 20°C (68°F)]

Checking The Operation
1. Remove the throttle body.





2. Remove the stepper motor.





3. Connect the special tool (test harness) to the idle control motor connector.

4. Connect the positive + terminal of a power source (approximately 6V) to the white clip or the green clip.





5. Holding the idle control motor as shown in the illustration, connect the negative - terminal of the power source to each clip in the sequence described below, and check whether or not there is vibration (a feeling of very slight shaking of the stepper motor) as a result of activation of the stepper motor.

a. Connect the negative (-) terminal of the power source to the red and black clips.
b. Connect the negative (-) terminal of the power source to the blue and black clips.
c. Connect the negative (-) terminal of the power source to the blue and yellow clips.
d. Connect the negative (-) terminal of the power source to the red and yellow clips.
e. Connect the negative (-) terminal of the power source to the red and black clips.
f. Repeat the test in the reverse (e - a) sequence.

6. If, as a result of this test, vibration is felt, the stepper motor can be considered to be normal.

TROUBLESHOOTING HINTS
- If the number of stepper motor steps increases to 100 - 120 steps or decreases to 0 step, the cause may be presumed to be a malfunction of the stepper motor or damaged or disconnected wiring of the harness.
- If the number of stepper motor steps deviates from the standard value even though the results of the checking of the harness of the idle air control motor and of the component itself indicate no abnormal condition, the cause may be presumed to be one of the following.
- Improper adjustment of the standard idling speed.
- Deposits adhered to the throttle valve.
- Vacuum leak.
- Improper sealing of EGR valve seat.
- Incomplete combustion within the cylinder. (Malfunction of the spark plugs, the ignition coil, the injectors, the compression)
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