A 2005 Volkswagen Passat 2.8V6 automatic car with a mileage of over 240 thousand km, equipped with BBG engine and 01V automatic transmission. Users reflect: the car suddenly appeared into the gear impact, and was unable to accelerate. After taking the car: the maintenance personnel carried on the basic inspection of the car. After opening the ignition switch, no matter what position the shift lever is in, the D screen is displayed in the dashboard display screen. Check the transmission control unit J217, which can not be entered. Instead of detecting the engine control unit, it is found that the fault code 013 is ingenious - it loses communication with the transmission control unit. Read 125 sets of data, the value is 1, indicating that the engine and transmission control unit can communicate. The gateway control unit J533 is retested, and the fault code is the same as in the engine control unit, and the control unit can also communicate between the control unit and the transmission control unit at this time. This indicates that the fault of the transmission control unit is accidental. Considering that the transmission control unit of the Passat car is installed under the front passenger seat, it is often damaged by water intake. So he pulled the carpet out of the J217 and found that there was no trace of water. The replacement test of J217 with 1.8 automatic block cars in the workshop is carried out. It is found that the screen display is restored to normal and the diagnostic instrument can also enter J217. Starting the engine, the shift display becomes a red screen immediately, and the ABS and ESP alarm lights are lit. The test found that there was a shock. The transmission control unit is detected and the fault code P1841---- is found to be out of line with the transmission control unit. The V6 model is different from the engine torque characteristics of the 1.8 models. Therefore, although J217 terminals are the same as the lead wires, the part numbers are different and the software versions are different. The part number of the V6 vehicle J217 is 8D0 927156DJ, the software version number is RdW 1111, the J217 part number of the 1.8T model is 3BO 927 156CH, and the software version number is RdW2222. Despite these differences, the failure of the transmission control unit has been determined by the above tests. Troubleshooting: Troubleshooting after changing the transmission control unit and matching it.