A mileage of about about 120,000 km, automatic transmission configuration 01V B52.8L Passat sedan. The car can not shift automatic transmission due to plant maintenance. After receiving the car: the road test and found that the car is always locked in 4th gear. Read diagnostic trouble codes using 5054a found P0753N88 switch or circuit breaker connected to the solenoid valve poor and can not afford to clear. In 01V automatic transmission, a total of seven solenoid valves, wherein N88, N89, N90 of the switching solenoid valve, N215, N216, N217, N218 of the linear solenoid valve, N215 main oil pressure regulator valve, N218 is the torque converter lock stop control solenoid valve, N216 and N217 solenoid valves control the C and G brakes brakes, while switching solenoid valve N88, N89, N90 by logical combination to control the other clutches and brakes. Can be clearly seen from the table, when all the solenoid valves do not work, the automatic transmission is locked in fourth gear. Based fault codes tips on N88 solenoid valves and circuits. N88 solenoid valve coil resistance is around 30a, from the ECU to the solenoid valve harness resistance is 0.10, but not on the ground or shorted to the cathode, is still the problem of N88 solenoid valve harness? Later, the N88 and N90 solenoid valve solenoid valve reversed, the fault persists. Line is not unusual, the solenoid valve is not a problem, is it a problem ECU (J217) of? Finally, replace the J217, after re-encoding match, failure to completely ruled out. It seems that the failure was due to the negative line N88 solenoid valve open circuit occurs in the ECU control circuit triggered Ground fault codes, because N88 solenoid valve does not work properly, thus affecting the normal shift automatic transmission, the transmission ECU had to be Lock Control, to prevent transmission damage.