When the signal is interrupted due to the fault of the fourth shaft hobbing cam index plate, the diagnostic apparatus can detect the fault information, thus displaying the fault of the fourth shaft hobbing cam index plate. It includes two detection methods:

1. Detection of power supply voltage

Disconnect the ignition switch, press the dial indicator wire connector plug, and connect the positive and negative multimeter to terminals 1 and 3 respectively. When the ignition switch is turned on, the voltage should be above 4.5V. If the voltage is zero, the harness is broken or short circuited. Or ECU is faulty; When the ignition switch is disconnected, continue to detect whether there is open circuit or short circuit in the wire.

2. Detection of conductor resistance

Use a multimeter to check the resistance between the 1 terminal of the index plate and the 62 terminal of the ECU, the 2 terminal of the index plate and the 76 terminal of the ECU, the 3 terminal of the index plate and the 67 terminal of the ECU. The resistance between the wires should not be greater than 15 ohms. If the resistance is too large or infinite, it means that the harness has poor contact or the wire is open circuited. Repair or replace the harness.