Symptom: the car dashboard on a variety of fault warning lights kept flashing alarm, in the steering operation, the sense of steering has become heavy.
    Troubleshooting: First connect the special fault diagnosis V. A. (17), airbag (15), ABS (03), and steering assist (44) systems, the D15 has been found to have failed to enter the instrument. Later, I use the diagnostic instrument into the engine electronic control system (01) for testing, the results of the system trouble-free memory storage. After entering the vehicle network control unit (09), found two fault code: 01312 - data bus driver is damaged; 01309 - steering power control unit J500 no communication. Continue to enter the gateway (19), also found two identical fault codes. According to the prompt code, I first measured the vehicle network control unit J519 T16A / 3 to the combination of instrument T32A / 7 of the wire, the results of normal lines. Later, I also measured the J519 T16A / 5 to the combination of T32A / 8 instrument between the wire connection, did not find the problem. According to the inspection results, I suspect Gateway J533 damage. Because the gateway J533 installed in the car network control unit J519, in order to replace the gateway, only with the vehicle network control unit J519 together with the replacement. But in the J519 to replace, the results are very disappointing, the fault still exists. According to the previous fault code, the fault may also be related to the steering power control unit. So I will turn to the power control unit J500 on the T4AL plug unplug and observe the dashboard, the results found that in addition to turn to help the alarm light, the rest of the warning lights are extinguished.
    Troubleshooting: Troubleshoot after replacing the steering assist unit.
    Maintenance analysis: In the Shanghai Volkswagen POLO sedan used CAN-BUS system, the system control unit between the use of copper serial connection mode, that is, the control unit are connected together, because the control unit between the information The propagation mode is broadcast transmission, so that after a certain control unit sends out the information, the receiving control unit freely chooses whether to receive the information. Because the CAN transceiver is installed inside the control unit, it has the function of receiving and sending. The car's combination of instruments, ABS, airbags and steering help belong to the same drive system, all in a data line. As the steering power control unit is damaged, so that other control units are unable to communicate, this fault belongs to the CAN-BUS system in the control unit line short circuit.