BMW 523Li car can not be started overhaul

     Check Analysis: maintenance personnel test and found that the starter will not turn, like a lack of battery power. After charging the battery, the engine smooth start. Detecting an engine control unit, found fault code 0820E8 ---- KI.30F Mains bus reset or shutdown; 93076A ---- K1.15 Mains bus off; 93076B ---- K130B Mains bus off; 802103-- - Junction Box control unit power supply voltage is too high; 930AC1 ---- Communication Interface signals are invalid and S5201- ignition coil. BMW Scanner V1.4.0 fault diagnostic ISID observed by the supply voltage, and found to be 15.00V, after a period of time rose to 17.00V, abnormal. At this time of the control unit to start recording overvoltage fault, the dashboard malfunction lights. After the flame is restarted, the power supply voltage down to about 12V. Apparently this time the generator is not power, if things go on, the battery power will soon be exhausted.

     According to the test plan, carry out functional tests on the generator. Then the actual output voltage of the generator is 11.80V, a temperature of 64 ℃, the output current of 0.0A, load rate of 3.1%, while the output current of the battery but for 130.2A. Judging from the generator is no longer working, but the battery output current data looks very strange.

     According detection alerts, if it is confirmed the generator is damaged, you will need to replace the generator. However, considering the relatively high cost of replacing the generator, if it was, but not solve the problem, the user will not confessed. We decided to withdraw from the test plan, and then look at the other DTCs.

     We observed that in addition to the DTC DTC brownouts and overvoltage tips, there is an ignition coil. But the situation was observed when the engine is idling, BMW Scanner found no shortage of cylinders jitter. Conflicting results between the ignition coil failure fault code.

     Holding a skeptical attitude towards the ignition coil failure considerations. See related information, after that, the generator is controlled via a data bus. Electromagnetic interference signal generated when the work if the ignition coil is too strong, the signal on the data bus will be disturbed. As a result, the data transmission between the engine control unit and generator control unit, an error occurs when the generator output voltage which is high low close.

     With a normal car ignition coil replacement do the test, we found that the fault completely disappeared. Thus, the ignition coil is indeed caused by a series of strange phenomenon.

     Troubleshooting: replace all the ignition coil, test confirmed troubleshooting.