An approximately 160,000 km mileage 2004 BMW X3E83SUV. Users report: car instrument airbag fault warning lights, cab lights sometimes flicker, front and rear wiper operation weakness, often stuck in the middle of the glass does not move.
After the pick fault content is read by ISID :50-MRS supply voltage; 8C-KOMBI moldings R; 87-KOMBIK bus; 30-GMK bus. Failure to read the content from the perspective of the detector in addition to “50-MRS supply voltage” Others are more abstract failures content, Symptom vehicle from the surface nothing seems implicated, so he decided to choose the airbag fault first, the phenomenon of exclusion. Select “50-MRS supply voltage” testing program execution, inspection program first analyzes the fault stored in the memory of the memory voltage is too low, if the supply voltage exceeds the 20s MRS is less than 9V, MR will store this fault, where MRS is the airbag The control unit or multi-occupant protection system control unit. Continue the inspection program, the detector gives a circuit diagram of the airbag system shown in Figure 1, and is recommended to check the battery voltage, battery check circuit diagram of a voltage with a voltage of 12.8V, normal. Tips for inspection in accordance with the circuit diagram of F11 MRS insurance, the insurance did not fuse. In accordance with the test plan to continue down analysis, whether between MRS supply terminal X74 of 57 feet and a ground supply voltage 9 ~ 16V, using a multimeter to measure voltage 57 between the foot and the ground terminal is only 5 ~ 8V, followed by measure the voltage X10016 22-pin terminal, F11 insurance and ground, the result is only 5 ~ 8V, it is clear that there is power failure MRS. MRS is powered by the battery through the ignition switch provides direct R block, as shown in the ignition switch in the position of a radio block diagram of the F11 is the insurance supply terminal R block shown in Figure 2. R-side airbag system not only to the insurance F11 power, but also for several systems powered A1 fuse distributor of F5 ~ F15’s. Since the F11 is only 5 ~ 8V supply voltage, and that several other insurance system is not only 5 ~ 8V supply voltage it? Measurements and inferred as, F5, and several fuses are also only 5 ~ 8V supply voltage. View schematics to find the fuse F9 is powered body basic module, and flying fuse wiper relay is controlled by the body basic module for the interior lights powered F6. Symptom several vehicles, seemingly unrelated, are actually the cause of the power supply voltage is too low skp-900.
R block is rotated by a mechanical key mechanical ignition lock, ignition switch by changing the linkage of internal contact position control, a common cause of failure is mostly inside the ignition switch contacts wear or erosion caused. To verify the empirical analysis is correct, the maintenance staff while measuring the voltage at A1 distributor, while shaking the ignition switch, then found Al multimeter measured at the supply voltage constantly varies between 5 ~ 11V, then check to make sure the ignition switch after the connection terminal is no problem, indeed the point of failure is the ignition switch.
Replace the ignition switch, troubleshooting.This story originally appeared on https://superobdskp900.wordpress.com