A Audi A4L car that runs about 9000km. User reflection: the car ESP fault light alarm. After receiving the car, the fault code is used to detect the fault code of the steering angle sensor G85 with 5052 ABS and the steering column control unit, and the operation is carried out according to the guided fault query. The 5052 indicates the initialization of the G85, but the fault code still exists after the initialization is completed, and the initialization fails. ABS system unit measurement value 5 group 1 area is 0, because the vehicle is an accident vehicle, disassembled and installed G85 and steering column cross shaft, the original vehicle parts assembly after the failure. Use 5052 to enter the 16 direction disk electronic control unit, observe the measured value data block and record it well, then enter the steering wheel electronic control unit of another normal vehicle, and observe the measured value to record it well. By comparing the measured data blocks, the anomalies are found: the 31 sets of measured values are 819.09 degrees at any angle, while the normal steering wheel is 0, and the left and right limit is 522.07 degrees. Remove and disassemble the G85, and observe that the driving arm of the internal photoelectric sensor has slid out the spiral guide. After the drive arm is rearranged to the center point, the G85 is assembled and the 31 sets of measured values are observed, still 819.09 degrees. At this time, it is determined that the G85 has been damaged and can not be repaired. But the original G85 only simple disassembly should not be suddenly damaged, again the G85 decomposition and careful observation, found in the G85 internal center of the guide of a total of 4 laps of angle, that is, the photoelectric sensor driven arm can only turn right two circles or turn left two circles to the limit of the guide. But the spiral coil inside the G85 has 6 circles of angles, that is, the spiral coil will turn right or 3 turns on the steering wheel or turn left for 3 times.