What does BCU failure mean?
4 Answers
BCU refers to the mainboard failure in the vehicle's battery management system. BCU is Baidu's dedicated computing platform for autonomous driving, featuring two fundamental capabilities—information security and cloud updates—along with three core AI modules: high-precision positioning, environmental perception, and planning decision-making. The solution is as follows: Fault diagnosis: Based on the symptoms, if the engine fails to start after stalling, it is generally caused by a fuel system or ignition system malfunction. Turn the ignition switch to the ON (II) position and check the fuel pressure at 370 kPa, which is normal. Ignition system inspection: Inspect the engine ignition system and observe no high-voltage spark, indicating an ignition system fault. Turn the ignition switch: First, turn the ignition switch to ON and use a test light to check terminal No. 1 of the ignition coil connector. If the test light does not illuminate, it indicates a power supply circuit fault in the ignition system. Test the ignition coil: Check that the No. 2 (15A) fuse under the instrument fuse box is intact. Remove the ignition coil for testing and find a faulty ignition coil relay. Replace the sensor: Replace the CKP sensor, clear the fault code using HDS, and reset the ECM/PCM. The engine starts normally, and the fault is resolved.
That day while driving, I suddenly found that the car window wouldn't close, the wipers were out of control, and the dashboard displayed a BCU fault warning. After checking the manual, I learned that BCU stands for Body Control Module, which is like the nervous system of the car, managing functions such as windows, headlights, and central locking. The most common issues are loose module connectors or water corrosion, and older cars are prone to wiring aging. Last time I encountered this, I went straight to the shop for a computer diagnosis and found that the rain sensor had short-circuited and burned out the module. Now, every time I wash the car, I make sure no water seeps into the dashboard, as replacing a new module can cost several thousand yuan.
After working in the auto repair industry for a long time, there are basically three steps to diagnose BCU errors: first, check if the relevant fuses in the fuse box are blown; then use a diagnostic tool to read the specific fault codes; finally, test the circuit voltage. The body control module manages twenty to thirty electronic functions—issues like erratic wipers, faulty door locks, or abnormal lighting could all stem from it. Common problems include swollen capacitors on the control board, program glitches, and worn-out wiring harnesses causing short circuits. Last week, I fixed a flood-damaged car where a clogged drain valve led to water accumulation that ruined the BCU, causing all the lights to flicker randomly. A reminder: remember to clean the sunroof drainage pipes before the rainy season.
My car's last BCU failure really screwed me over! On my way to pick up a client, the windows suddenly rolled all the way down, and heavy rain poured directly into the car. At the 4S shop, the diagnosis was that the improperly installed wiring of the aftermarket dash cam caused a power overload, which fried the Body Control Module. The BCU in modern cars acts like a general manager, integrating functions that used to be handled by separate relays. The most common symptom when it fails is several unrelated functions malfunctioning simultaneously, like your wipers turning on but the rearview mirror heating activating by itself. Replacing the module costs two to three thousand yuan, and now I always have professional shops handle any electrical modifications.
