What is the function of the MLC hole in a car?
2 Answers
The "MLC" hole on a car's onboard unit is a simple sound source (speaker) installed inside the unit, primarily used to provide keypress tones during operation or error operation prompts. It is also sometimes used as a Bluetooth voice sound source, which is more common in older models. Nowadays, Bluetooth phone audio can typically be routed to the car's audio system speakers, making it more convenient and clearer for safe driving. Additional information: The "Res" hole on a car's onboard unit is mainly used for recovery or restart purposes, such as when the unit "freezes" during operation; when a "serious error" occurs due to operational mistakes or internal machine issues; as a "special" button during certain onboard unit upgrades; or as a button to restore initial settings when the machine becomes slow due to prolonged use, high memory usage, etc.: releasing memory, restarting, etc.; some special design requirements for certain functions.
A few days ago, I studied this MLC hole, which is actually that inconspicuous small hole on the edge of the engine hood. Its main function is to allow the probe of the LiDAR calibration device to extend inside for calibration, typically used during vehicle manufacturing or professional repairs. I remember last year when I accompanied a friend to the 4S shop, the technician set up laser equipment in the service area and connected to the internal sensor through this small hole. Normally, car owners don’t need to worry about this hole, but if you notice the sealing ring around the hole has fallen off, it’s best to get it fixed to avoid water leakage during rainy days. By the way, some older car models have this hole as a solid decorative cover—definitely don’t poke it randomly yourself.
