Do it yourself
Frequently asked questions about cars and motorcycles
Car tutorial (Do it yourself) Motorcycle tutorial (Do it yourself) Frequently Asked Questions

How an Inertia Switch (or Impact Sensor) Works

Model: (Various brands) Various
Part: Checks and maintenance

The physical principle of the inertia switch is based on the law of inertia (the first principle of dynamics) whereby a body tends to maintain its state of rest or uniform straight motion until acted upon by an external force. Inside the sensor, there is a moving mass that normally remains at rest. When a sudden deceleration occurs, the mass continues to move forward, shifting from its resting position; it is usually a small ball on an inclined ramp with a slight drop and two electrical contacts. In its normal state, the ball is held in a cavity, and no electrical contact is made. In the event of an impact, the ball rolls down the ramp, overcoming the barrier and closing the circuit of the fuel pump to prevent fires. This signal is then detected by the ECU.

Posted on 31 May 2026 by ScegliAuto

Video tutorial

Related tutorials

How to Reset the Inertia Switch on an Alfa Romeo
How to Reset the Inertia Switch on an Alfa Romeo
(Various brands) Various In this video, you will see the procedure to reset the inertia switch in case of an accident or accidental activation. This switch is designed to cut…
How the Temperature Sensor Circuit Works
How the Temperature Sensor Circuit Works
(Various brands) Various Let's see how the temperature sensor circuit works: electrical energy is supplied by the battery; the ignition key acts as a switch, while the fuse i…
How to Replace the Front Impact Sensor?
How to Replace the Front Impact Sensor?
(Various brands) Various To remove the front impact sensor of the car, first, remove the front bumper and the left front headlamp by unscrewing the relevant securing screws a…

Other guides you may be interested in

    Frequently Asked Questions

    • Vari - What does it mean when the message "insp" appears on a car? Read answer
    • Vari - Why doesn't the Becker Map Pilot start? Read answer
    • Vari - What problems does the Kymco Downtown 300i have? Read answer

How to Check the Oil Level on a Jeep Renegade?

To check the oil level on a Jeep Renegade, you need to open the bonnet to access the components inside the engine bay: on the lower left side of the engine block, you will find the dipstick for checking the level. This should be pulled out and thoroughly cleaned with a cloth: once cleaned, reinsert it back into its tube and pull it out immediately after. This way, you can check that the oil mark is between the minimum and maximum levels; finally, you can place the dipstick back in its tube.

Watch the video!


by ScegliAuto

More videos