Where is the power module located in the BMW 4 Series?
3 Answers
BMW 4 Series power module is located under the trunk, which can be seen by opening the trunk. Introduction to power module: A power module is a power converter that can be directly mounted on a printed circuit board. As power supplies tend to be modularized and miniaturized, power modules have emerged. With the highest level of integration, the main circuit of the switching power supply is integrated into the chip, enabling functions such as wide-frequency modulation, isolation, and various protections. Function of automotive power module: It measures the difference between the actual output voltage and the nominal output voltage of the module. While achieving voltage conversion and power transmission, it also measures its own losses. It monitors the state of the output voltage establishment process or stabilization process when the power module is turned on.
As a seasoned mechanic who often helps friends with car repairs, the power module of the BMW 4 Series is mainly hidden in a spot you might overlook: under the right-side trim panel in the trunk. Lift the felt layer, and you'll see the battery itself, with the black box next to it being the power distribution unit. Interestingly, BMW designers placed such a heavy component at the rear to balance the car's weight distribution and enhance cornering stability. I've encountered several cases where owners modified their audio systems, causing fuses to blow—always disconnect the battery's negative terminal before repairs. Note that the location may vary slightly across different model years of the 4 Series, but post-2014 models are generally in this spot. If replacing the battery yourself, be sure to reset the power module with professional equipment, or the start-stop system will malfunction.
Last month, I just replaced the battery in my 4 Series. Its power module is located on the right side of the trunk, visible after lifting the floor mat. This position is quite cleverly designed, avoiding the high temperatures of the engine bay while also benefiting the vehicle's balance. During maintenance, be careful as the plastic clips are prone to breaking—I had to make an extra trip to the auto parts store for replacements because of this. The power module actually includes the battery and a distribution box, with those colorful fuses inside corresponding to different circuits. Last time when the headlights weren't working, it turned out to be a blown 15A fuse here. If you're doing it yourself, prepare a T20 Torx screwdriver, and remember to keep the car key far away before operating, otherwise the system will throw a fault code.
