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A BYD S7, customer feedback: After the car is parked, the vehicle in gear will not move. After the vehicle is put into gear, release the brake pedal and drive for 3 nm, and it will not move! Turn off the fire and restart, the fault phenomenon is the same, you can't drive, ask for help.

Cause analysis:

1, low battery voltage fault;

2, gearbox program failure;

3, electro-hydraulic module or clutch failure;

4. Engine failure.

Maintenance process:

Arriving at the vehicle site, the reading system is trouble-free. The transmission version number is A6 version, and it is upgraded to A8 version! The fault is still the same, the trailer will go back to the store for processing! Measure the pressure values of the battery and clutch, and there is nothing abnormal! Moreover, the engine speed is only 4 revolutions, and the air conditioner is not cooled. In severe cases, flameout will occur. Reading the data flow of the engine and transmission found nothing unusual. The engine speed can reach 3,800 rpm when stepping on the accelerator in P or N gear, so nothing unusual was found, except that the intake pressure was only 28kpa sometimes when stepping on the accelerator, and only 22kpa in severe cases. Because the turbocharger intervened when the vehicle accelerated, the intake pressure became smaller, so no abnormality was found! Because the reason can't be found, we try to switch the electro-hydraulic module and carry out TCU test on the gearbox. The fault remains, and vehicle maintenance has entered a difficult period. Calm down and check it again. Is it caused by insufficient intake pressure of the engine? Remove the throttle inlet hose for testing and troubleshooting! After checking the gas path, it was found that four fifths of the oil was filled in the intercooler, and it was found that the reason was that the turbocharger leaked oil. Therefore, it is judged that the oil leakage of the turbocharger causes the intercooler to be filled with most of the engine oil, resulting in insufficient intake pressure, unsatisfactory working speeds of the air-conditioning compressor and transmission, and the vehicle is stuck. Replace the turbocharger, clean the intercooler oil and solve the problem!

Maintenance summary: When the maintenance fault encounters setbacks, we should think calmly and find the fault point.