Acura CMBS indicator

How to read it

Acura’s 2021 RDX manual says CMBS can assist when the car may collide with a vehicle or a pedestrian detected in front of it. It is designed to alert the driver when it determines that a collision is possible, and to reduce speed to help minimize the severity of a collision it deems unavoidable. When the driver switches CMBS off, the indicator comes on and a message shows on the multi-information display for five seconds. CMBS is on again every time the engine is started. On the 2019 TLX the indicator also comes on for a few seconds when the power mode is set to ON, then goes off.

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When it comes on

The 2021 RDX and 2019 TLX manuals give the same reasons for a light that stays on: a problem with CMBS, or CMBS shutting itself off. The RDX manual says it shuts itself off while the temperature inside the camera is too high, or while the area around the camera or the radar sensor is blocked by dirt or mud, and that the indicator can take some time to go off after the radar sensor is cleaned. It may also come on for a while in an enclosed space such as a tunnel, or when the Maximum Load Limit is exceeded. On the 2025 MDX, CMBS can’t be switched off while driving, and when it shuts itself off the amber Safety Support indicator comes on and stays on.

What the manual says to do

For an indicator that stays on although CMBS hasn’t been switched off, the 2021 RDX manual says: “Stays on constantly without the CMBS™ OFF - Have your vehicle checked by a dealer.”

What NHTSA calls it

NHTSA calls a system like CMBS automatic emergency braking, which applies the brakes automatically when a forward collision is imminent. NHTSA notes that makers use different names for the same driver assistance technologies.

What the US standard says

FMVSS 127, the US standard for automatic emergency braking in light vehicles, applies to vehicles manufactured on or after 1 September 2029, later than any Acura on this page. It requires the system to watch continuously for its own malfunctions, including a blocked sensor, and to show the driver a telltale when it finds one. A control that switches the system off is allowed only in the cases the standard lists: a vehicle owned by a law enforcement agency, low-range four-wheel drive, a tow mode, or another system that would interfere with emergency braking. At each new ignition cycle the system must return to its default mode.