G-Sensor in Dash Cams: What It Does and How to Set It

Why the G-sensor matters

Motor vehicle crashes are still a leading cause of death in the United States. The CDC reports that more than 120 people are killed in motor vehicle crashes every day, and IIHS counted 39,254 lives lost in crashes in 2024. A dash cam cannot prevent those crashes, but it can give you an independent record of what happened. The G-sensor is the part of the dash cam that decides when that record needs special protection.

The G-sensor is an accelerometer. It monitors sudden changes in the vehicle's speed or direction. If the sensor sees an impact, a hard brake, or another sharp movement, it marks the current footage as an event. Event footage is protected so normal loop recording does not write over it.

Without a G-sensor, a collision clip could be treated like any other minute of driving and eventually be erased. With it, the camera keeps a separate record that you can review later. That is why sensitivity matters: a sensor set too high protects too much, and a sensor set too low may not protect the clip you need.

How impact detection works

In everyday driving, the car is always moving: accelerating, braking, cornering, and vibrating over the road. The accelerometer inside the dash cam measures these forces. The camera compares what it sees to an internal threshold. When the force passes that threshold, the G-sensor triggers emergency recording.

Emergency recording usually saves the current clip to a locked event folder. Some dash cams also save a pre-buffered clip from the seconds before the trigger, so you can see what happened just before the impact. In a multi-channel system, the event can include footage from more than one camera at the same time.

The threshold is often adjustable in the camera settings. A high sensitivity setting lowers the threshold, so small bumps and light contact can trigger an event. A low sensitivity setting raises the threshold, so only stronger impacts are marked. The right setting depends on where you drive, how you park, and how often you want to review event files.

Sensitivity settings and how to choose

Most dash cams offer at least three sensitivity levels: high, medium, and low. Medium is a sensible starting point for daily driving. It is sensitive enough to catch a collision or hard braking event, but not so sensitive that every pothole or railroad crossing creates a protected file.

High sensitivity is more useful for unattended parking. If someone bumps your car in a lot, you want the camera to notice even a light impact. This is especially important if you rely on parking mode or motion detection while the vehicle is parked.

Low sensitivity is worth considering if you frequently drive on rough roads. Too many false events can fill the event folder and make the camera beep or flash more often. If you notice that, move to a lower setting. You can also check whether the camera has separate sensitivity settings for driving and parking, since a single setting may not fit both situations.

Emergency recording and file protection

When the G-sensor triggers, the dash cam moves the clip into a protected area instead of letting loop recording overwrite it. This event file is meant to survive normal recording cycles. On some cameras, event files are stored in a separate folder or on a different part of the microSD card.

Protected event files still take up space. If the sensitivity is high and the vehicle is parked on a busy street, the camera may generate many event files. Over time, these can fill the card. It is a good idea to review event files periodically and clear the ones you no longer need. A high-endurance microSD card is often recommended for dash cams because continuous recording and event writing put extra stress on storage.

Some dash cams let you format the card or delete protected files through the menu. Others manage the event folder automatically when space runs low. If your event folder fills quickly, the first thing to change is sensitivity, not storage.

Parking mode and the G-sensor

The G-sensor plays a central role in parking mode. When the engine is off, the camera may enter a low-power state to save energy. It can wake up when the G-sensor detects a bump, when motion detection sees movement, or when both are enabled. A bump in a parking lot is often the clearest warning that a collision just happened.

Parking mode does not run forever on the car battery alone. A dash cam with parking mode usually needs a hardwire kit or an external power source. Without reliable power, the camera may shut down before an impact occurs. If you want impact protection while parked, look for a dash cam that supports parking mode and has a power plan that fits your car.

Check the camera's menu for a separate parking sensitivity setting. Some dash cams let you set a higher G-sensor sensitivity for parked recording and a normal sensitivity for driving. That can give you strong protection in the lot without producing false events on every drive.

How to set your G-sensor

Start with the default or medium sensitivity and adjust after a few days. Pay attention to the alerts and event files the camera creates. If you are seeing many events on smooth roads, lower the sensitivity. If a clip you expected to be protected is missing, raise it.

Use this as a starting point:

Medium is a good default for daily driving. High works better for parked vehicles and light impacts. Low helps on rough roads or when false alerts are a problem. Review event files periodically so the protected folder does not fill up. Learn how your camera responds before you need the footage.

• Medium is a good default for daily driving.
• High works better for parked vehicles and light impacts.
• Low helps on rough roads or when false alerts are a problem.
• Review event files periodically so the protected folder does not fill up.
• Learn how your camera responds before you need the footage.

What to pick for your use

Questions

What does the G-sensor do on a dash cam?

It detects sudden acceleration, braking, or impact and marks the current footage as an event. The event file is protected from normal loop recording so you can review it later.

What is the best G-sensor sensitivity setting?

Medium is a good starting point for most drivers. Use high for parking mode if you want to catch light impacts. Use low if you get too many false events on rough roads.

Does the G-sensor work while the car is parked?

It can, if the dash cam has parking mode and enough power. In parking mode the camera may wake up when the G-sensor detects a bump. A hardwire kit or external battery can keep it running.

Why does my dash cam keep saving event files?

The sensitivity is probably too high for your driving conditions. Lower the G-sensor setting to reduce false events. You may also want to clear the event folder periodically.

Will lowering the G-sensor cause me to miss a crash?

It can, if the impact is very light. Low sensitivity filters out small bumps, but a real collision is usually strong enough to trigger the sensor. Test the setting to see what it catches.