Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
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20.
DTC P0704 Clutch signals are unreliable.
Fault Description: Transmission control unit (TCU) is integrated with engine control unit (ECU) and calculates
optimal time and speed for clutch engagement according to feedback information from sensors of accelerator pedal,
transmission gear position, transmission input/output shaft speed, engine speed, throttle opening and etc. Automatic
transmission (AT) actuating mechanism consists of electric oil pump, solenoid valve and clutch cylinder. When ECU
gives command to drive electric oil pump, high-pressure fluid generated in the pump goes through solenoid valve and
gets into clutch cylinder. ECU controls magnitude of current of solenoid valve for the control of fluid flow and fluid
passage change. Thus piston movement of clutch cylinder is realized in order to complete clutch operation during
vehicle starting and shift. In the case of inconformity between clutch signal and actual condition, DTC occurs.
Diagnosis Hint: clutch switch fault
Check switch wire harness (Check Terminal 58 of ECU for open circuit, short circuit and poor contact.)
Check switch power supply voltage and operation condition.
Determine ECU replacement according to actual condition.
Terminals ECU
K55 Clutch switch signal
Clutch switch
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