'How do immobilizers work?' [Newbie Guide]

Updated Apr 15, 2021 | Same topic: Beginner's Guide

That flashing icon when your car is locked should give you peace of mind.

A car is a serious financial decision, which is why we take great pains to ensure that it’s protected against unwanted intrusion. Door locks are a default feature towards this end, but those only prevent unauthorized entry inside the vehicle.

Car theft

This is one of the things you wouldn't want happening to your car

To keep the car from actually being driven off by thieves, it needs something a little more sophisticated. Enter the immobilizer. It’s a form of electronic security that allows the car’s engine to be started only in the presence of the authorized key, otherwise, the vehicle is immobilized.

Immobilizers have been around longer than many people think. The first one was patented in 1919, using double-contact switches that needed to be connected in a certain order; otherwise, the engine could not be started and the alarm will be triggered.

The system settings can be changed on every occasion the car was driven. Modern immobilizers use rolling codes that change automatically without driver intervention.

Immobilizer 1919

The first car immobilizer was patented in 1919

How does it work? A standard immobilizer is made up of two components: a transponder within the key fob and a receiver inside the vehicle’s ECU. The key fob’s transponder contains the necessary electronic security code or password.

For every attempt to start the engine, the vehicle’s receiver sends a request to the key fob, and if the transponder returns the correct code, the ECU activates the fuel system and ignition circuit, allowing you to start the car. If the codes don’t match, no ignition takes place.

Key fob

The key fob has a transponder that holds the correct code for the car to start

Some higher-end models have immobilizers that use two-tier security, comprising a permanent personal code and a second, alterable code. The system changes the second code and stores it in the key each time the engine is started.

If both codes match, the engine is started. Even if only one of the codes ends up matching, the engine will be unable to start, preventing vehicle theft.

When the car is locked, you’ll probably notice the immobilizer icon flashing on the instrument panel.

This is normal since it shows that the feature is in operation and is busy protecting your vehicle, serving as an effective visual deterrent against would-be thieves. And no, it doesn’t affect your car’s battery consumption that much.

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Joseph Paolo Estabillo

Joseph Paolo Estabillo


Joseph holds a degree in Journalism from the University of the Philippines Diliman and has been writing professionally since 1999. He has written episodes for CNN Philippines' motoring show Drive, and has worked on corporate projects for MG Philippines and Pilipinas Shell. Aside from being Philkotse.com’s Content Lead, he also writes content for numerous car dealerships in the U.S., spanning multiple brands such as Alfa Romeo, Chrysler, Dodge, Jeep, and Maserati, among others.

Facebook: https://www.facebook.com/kapatilya

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