Idle Speed Control Motor Position Sensor
Operation
The idle speed control motor position sensor functions to convert the data concerning the position of the plunger (located within the idle- speed control motor) to voltage, and to input that voltage (as signals) to the engine control module. The engine control module, based upon those signals, then functions to regulate the idle-speed control motor.
The 5V power supply within the engine control module is supplied to the idle speed control position sensor; it then passes through the resistance within the sensor and is grounded at the engine control module
When the plunger located within the idle-speed control motor extends from its contracted condition, the resistance between the idle speed control motor position sensor's variable-resistance terminal and the ground terminal also increases in accordance with that extension. As a result, the voltage of the idle speed control motor position sensor's variable-resistance terminal also becomes higher in accordance with the extension.
Troubleshooting Hints
Hint 1:
The idle speed control motor position sensor is tne most important sensor for control of the idling speed; there is very often a malfunction of this sensor if a problem occurs when the engine load is caused to fluctuate, such as when, during idling, the air conditioning switch is switched back and forth between OFF and ON, etc.
Hint 2:
If the output voltage of the idle speed control motor position sensor deviates from the standard value even though the results of the checking of the idle speed control motor position sensor harness and of the component itself are normal, the malfunction may be presumed to be among the following:
(1) Improper adjustment ot the basic idling speed.
(2) Deposits adhering to the throttle valve.
(3) Air being taken into the intake manifold due to a gasket leak, etc.
(4) Improper seating of the EGR valve seat.
(5) Imcomplete combustion within a cylinder. (Malfunction of spark plugs, ignition coil, injectors, compression pressure, etc.)
Operation
ISC motor position sensor is a variable resistor type, and is integrated in the ISC motor system. The sliding pin of ISC motor position sensor is in contact with the end of the plunger. Therefore, as the plunger moves, the internal resistance of ISC motor position sensor varies. This leads to the variation of the output voltage. ISC motor position sensor detects the plunger position at the ISC motor system. and sends the signal to SCM. ECM processes the ISC motor position sensor signal, idle signal, coolant temperature signal, load signal )A/T & A/C) and vehicle speed signal to control the opening angle of the throttle valve and revoiution speed during en gine idlng.
Troubleshooting Hints
Since idling is not controlled when ISC motor position sensor is troubled, idling may not be evenly maintained.
Inspection
Harness inspection
Sensor Inspection
(1) Disconnect the idle speed control motor position sensor connector, and connect the special tool (test harness) to the connector an idle speed control motor position sensor side
(2) Measure the resistance between terminal 1 (black clip of special tool) and terminal 3 (white clip) of the idle speed control motor position sensor connector.
Standard value: 4-6 k/ohm
(3) Disconnect tne idle speed control motor connector.
(4) Connect a 6V DC power supply between terminals 1 and 2 of the idle speed control motor connector to activate (extend and retract) the idle speed control motor. Measure the resistance between terminal 1 (black clip of special tool) and terminal 2 (red clip) of the idle speed control motor position sensor connector.
Standard value: Smooth increase/decrease in accordance with extension and retraction of idle speed control motor plunger.
Caution: Apply only a 6V DC or lower voltage. Application of higher voltage could cause locking of the servo gears.
(5) If there is a deviation from the standard value, or if the cnange is not smooth, replace the idle speed control motor assembly.