Analysis of the phenomenon of engine fault light on

Analysis of the phenomenon of engine fault light on

    When the engine fault light is on and the engine electronic control unit memorizes fault code 4431, it is likely that the idle speed control system is defective. It is recommended that you check the line inspection, mechanical inspection, and component operation inspection of the idle speed control system according to the following methods.

    1 preprocessing step

    When the above failure phenomenon occurs, the throttle body should be thoroughly cleaned first, and the following inspections should be carried out.

    a. Check the intake manifold and vacuum line for leaks.

    b. Check whether the throttle valve action is in good condition.

    c. Use the red box MT2500 scanner to clear the fault code, conduct a road test for more than 5km, and then check whether the engine electronic control unit has the memory of the fault code. If the engine electronic control unit memorizes the fault code 4431 again, it can be determined that the idle speed control system is defective.

    2 line check

    a. Remove idle motor wire connector N71.

    b. Use the resistance gear of the multimeter to measure the resistance of the idling motor, the resistance value should be about 7~11Ω (the resistance value is about 7Ω when the car is cold, and the resistance value is about 11Ω when the car is hot).

    c. If the resistance value is not within the above standard range, the idle motor should be replaced.

    3 Mechanical inspection

    Remove the idle motor, connect the wire connector, turn on the ignition switch, and observe the rotary valve of the idle motor to see if it rotates smoothly from start to stop (Note: Do not use a screwdriver or wrench to move the rotary valve to avoid damage valve). If the rotation is not smooth, the idle motor should be replaced.

    4 Component Operation Check

    When there is no problem in the circuit inspection, carry out the component operation test.

    a. Remove the dust cover of the idling motor, use the VAG1551 special instrument for Volkswagen (VW) vehicles, and enter the "output component diagnostic test mode" (FUNCTION03-OUTPUTDIAGNOSTICTESTMODE) to test the actual operation of the idling motor.

    b. Connect the LED light between the idle motor No. 1 terminal and the ground terminal, and the LED light must be on.

    c. Connect the LED light between the No. 1 connector of the idle motor and the positive pole of the battery, and the LED light must be on.

    d. If the LED light does not light up, or the idle motor does not work, check the continuity between the wire connector of the engine electronic control unit and the corresponding terminals of the wire connector of the idle motor: Terminal 1 of the connector on the wire side of the idle motor and There should be continuity between the 11D terminals of the wire side connector of the engine electronic control unit; the No. 2 terminal of the idle motor wire side connector and the 7D terminal of the engine electronic control unit wire side connector should be connected.

    e. If the circuit is normal, but the idling motor does not rotate during the component action test, connect the external power supply to test the idling motor directly. If the idling motor is good and the wiring is good, but the idling motor still does not work, it means that the engine electronic control unit is faulty.

    f. After the repair is completed, clear the fault code and conduct a road test to confirm that the fault has been eliminated.