Failure phenomenon:
1. The wire between the main controller (MC), EC motor, and engine controller is faulty. Even if the engine controller rotates, the engine speed does not change.
2. Main controller and engine controller connector terminal diagram Main controller and engine controller connector terminal
Fault diagnosis and troubleshooting steps:
(1) Diagnose with the Dr.EX diagnostic analyzer and check whether the fault code 07 is displayed on the screen (07 indicates that the engine controller is faulty). If fault code 07 is displayed, the engine controller is faulty. Disconnect the engine controller connector, check whether the resistance between terminals 5 and 7 on the engine controller side is (5±0.5)k, and then turn the engine Connect the controller, insert the multimeter's test needle from the rear of the engine controller, and turn the engine controller to check the voltage change. Does the voltage reach 0.3~1.0V at the lowest speed position? Is the voltage at the highest speed position? Reaching 40~4.7V? If the resistance and voltage do not meet the requirements, it means that the engine controller is faulty, and the fault can be eliminated after replacement.
(2) If the resistance and voltage are within the specified range after the detection, but the fault still exists, the engine controller connector should be disconnected, and check whether the voltage between the terminal 5 and 7 of the wire end connector is (5±0.5) V (the key switch is in the ON position). If the voltage is not normal, continue to check whether the voltage between the terminal 5 of the wire end connector and the chassis is (5 ± 0.5) V (the key switch is in the ON position), if the voltage is still abnormal, the main controller and engine control The wire between the terminal 5 of the controller is broken. After repair or replacement, the fault can be eliminated; if the voltage is normal, it means that the wire between the main controller and the engine controller terminal 7 is broken. After repair or replacement, the fault can be eliminated.
(3) If the voltage between the terminals 5 and 7 of the wire end connector is in the range of (5±0.5) V (the key switch is in the ON position), then continue to check the main controller 22P connector terminal D21 and the engine controller terminal 6 Whether there is open circuit or short circuit. If there is no open circuit or short circuit, it means that the main controller is faulty (note: the engine speed adjustment and engine learning must be performed after replacing the main controller); if the open circuit or short circuit, the relevant excavator maintenance
(4) If the diagnostic code 07 is not displayed on the screen when starting diagnosis with the Dr.EX diagnostic analyzer, the lamp wire (part number is ST725. Connect the wire element with lamp between the connectors according to the operation process Whether the middle light is on or off to check whether the circuit is normal) Connect to the EC motor. When the engine controller is rotating, check whether the light is on. If the light is not on, it means that the main controller is faulty or the main controller and the EC motor The wire between is disconnected: If the light is on, the EC motor is faulty.
