What Is a G-Sensor on a Dash Cam?
October 17, 2026 · 7 min read
Your dash cam chimes at every railroad crossing, and the memory card is filling with clips you never asked it to save. If that chime is why you searched what is G sensor in dash cam settings, this guide explains what the sensor does, why it misfires, and which sensitivity suits your roads.
Updated — first published
Quick answer
A G-sensor in a dash cam is a three-axis accelerometer that measures sudden force, and when a jolt crosses the sensitivity threshold you set, the camera locks the current clip so loop recording cannot erase it. Use low or medium sensitivity for driving, because high sensitivity locks clips on ordinary potholes and fills the card.
Who this guide is for
This guide is for dash cam owners who want the G-sensor set correctly. No technical knowledge needed.
This is for you if
- Your camera beeps or shows a padlock icon over bumps
- Your event folder fills with clips of nothing
- You are unsure whether low, medium or high is safe
Look elsewhere if
- You want parked-car coverage: read do dash cams record when the car is off?
- You are choosing a camera. This covers one setting
How this guide was researched
Everything here comes from manufacturer manuals and support pages.
How this guide was researched
- Cedar Buy read manuals and support pages from BlackVue, Garmin and other dash cam makers in October 2026.
- The road-type table is editorial guidance built from what makers say about sensitivity and bumps, not measured false-lock rates.
- No g-force thresholds are given, because makers do not publish comparable ones.
- Specifications come from manufacturer documentation. Cedar Buy does not physically test products — see our editorial policy.
What the G-sensor on a dash cam does
A G-sensor (short for gravity sensor; technically an accelerometer) measures how hard the camera is pushed forward and back, side to side, and up and down. When force spikes past a set limit, it tells the camera to protect the footage.
It cannot tell a crash from a pothole or a slammed door; each is just a sudden jump in force.
How event locking works
Event locking moves the clip being recorded at the moment of a jolt out of the normal loop, so it is never overwritten. Normal loop recording saves segments, typically 1 to 3 minutes long, and erases the oldest when the card is full.
BlackVue says its event files keep several seconds from before and after the impact and are excluded from loop overwrite. Garmin’s manual files automatic incident clips in a 100EVENT folder while ordinary video is recycled.
A rear-end hit trips the sensor too, but a front-only camera locks footage of the road ahead, not the car behind. That gap is the whole question behind do you need a rear dash cam?
Sensitivity settings explained
Sensitivity sets how big a jolt must be before a clip locks: high reacts to small bumps, low waits for a hard hit. Most cameras offer off, low, medium and high.
Low catches crashes and little else
A collision produces far more force than a pothole, so low still locks it. Use it on rough roads.
Medium suits smooth roads
Medium also locks hard braking and sharp swerves, and rarely misfires on well-kept highways.
High belongs to parking mode
A parked car barely moves, so a door ding stands out. Driving on high fills the card with speed bumps.
Driving and parking are separate settings
BlackVue, for example, lists driving impact and parking impact as two controls. Set both.
Parking mode needs power with the engine off, usually from the fuse box, so read how to hardwire a dash cam.
False triggers on rough roads
A false trigger is a locked clip with no incident in it, and high sensitivity on rough roads produces them constantly. Potholes, railroad crossings, bridge joints and gravel washboard all spike the force. BlackVue warns that a setting that is too high records unneeded events from road bumps, while too low can miss impacts.
Step down one level rather than switching the sensor off. With it off, a crash is saved only if you press the lock button yourself.
Why a full card stops protecting you
Locked clips escape the loop, so false triggers pile up until the protected space runs out. Then, depending on the model, the camera either recycles the oldest locked clips or stops locking new ones.
Either way, a week of speed-bump clips can push out Monday’s fender bender or stop Friday’s crash from being saved. Copy and clear the event folder every few weeks.
Recommended setting by road type
Match the setting to your roughest regular road, not your smoothest.
| Road surface | Low | Medium | High | Set it to |
|---|---|---|---|---|
| Smooth highway | Rare false locks | Rare false locks | Locks on expansion joints | Medium |
| City streets with potholes | Rare false locks | Locks on deep potholes | Frequent false locks | Low or medium |
| Gravel or washboard | Locks on bad patches | Frequent false locks | Near-constant locking | Low |
| Off-road trails | Frequent false locks | Near-constant locking | Near-constant locking | Low, or off and lock by hand |
| Parked, engine off | May miss a door ding | Catches most bumps | Catches light contact | Medium or high |
The labels are not a standard
Low on one brand can be as touchy as medium on another; no industry standard defines the levels. Treat the table as a starting point.
Key terms, explained
Menus use different words for the same three ideas, which makes guides seem to disagree.
Plain-language definitions
- G-sensor (also called impact sensor or shock sensor)
- An accelerometer that measures sudden force on three axes, in g, where 1 g equals Earth’s gravity.
- Event file (also called a locked, protected or emergency clip)
- A clip moved out of loop recording. It stays until you delete it or format the card.
- Loop recording
- Recording in short segments, erasing the oldest unlocked one when the card fills.
Mistakes that cost you the footage
The costliest mistake is driving on high sensitivity, which buries the clip you need under pothole clips.
- Turning the G-sensor off to stop the beepingMute the chime and lower sensitivity one step instead.
- Never emptying the event folderCopy keepers to a computer, then format the card in the camera.
- Using one setting for driving and parkingA parking-level setting misfires constantly on the road.
Frequently asked questions
What does the G-sensor do on a dash cam?
It detects sudden force and locks the current clip so loop recording cannot overwrite it. The sensor is an accelerometer watching three directions of movement. When a jolt passes your sensitivity setting, the clip moves to a protected event folder, usually with a few seconds from before and after the impact.
Should my dash cam G-sensor be on high or low?
Low or medium for driving, medium or high for parking mode. A collision creates far more force than a pothole, so low still locks real crashes. High sensitivity while driving locks clips on ordinary bumps, filling the protected space on the card.
Why does my dash cam keep beeping and locking files?
The G-sensor sensitivity is too high for your roads. Every pothole or speed bump crosses the threshold, so the camera chimes and saves an event file. Lower driving sensitivity one level, drive your usual routes for a week, then count the new event files.
Set it, then check it after a week
Cedar Buy’s recommendation: set driving sensitivity to low if your roads are rough and medium if they are smooth, set parking separately, and then let your own week of driving decide.
After seven days, open the event folder: if it is full of bumps, drop one level. Then set a reminder to clear the folder every few weeks, so the space is free the day you need it.
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