What Is an Engine Immobiliser & How Does It Work?


Jun 26th, 2020

What Is an Engine Immobiliser & How Does It Work?

You've probably seen people hotwire a car a million times in movies. A guy breaks into a vehicle, connects a few wires under the steering wheel, and voila, the car starts, and they drive off. To correct this, manufacturers came up with the idea of fitting cars with engine immobilisers. 

All new vehicles sold in Australia from 2001 had to be fitted with engine immobilisers. They have been highly effective in curbing car thefts with an impressive reduction rate of more than 40%. And the icing on the cake: You can forget about your key being stuck in the ignition. To fully appreciate their essence, you have to know how they work.

How do engine immobilisers work?

The car keys distributed by dealerships today can be looked at as additional security features. The key fobs or smart keys contain transponder chips. These chips send a security code to the car's immobiliser system when you put it into the ignition or have the key fob inside the vehicle (If it's a push-to-start). The car will start if the security code in the key fob matches the one in the immobiliser system. Otherwise, your car will not hum to life.

Some manufacturers have even levelled up their immobilisers to a two-tier security system that has one permanent code and a second changing code. The second code is changed each time you start the vehicle and is saved in the transponder. When you want to start the car, the immobiliser first reads the permanent code then requests for the second (changing) code, and if it matches the one saved in the system, then it runs. Without the second code, the car will not start.


Sometimes the immobiliser might malfunction. If you experience these issues, the transponder may need replacing.

Unlocking and locking issues

If by any chance, your remote unlock fails you, the immobiliser may be damaged. Also, if you find it impossible to lock the car using the smart key, you will need to have it checked.

Key in the ignition won't turn

If your key fob has a physical key that you must insert in the ignition and after inserting you notice that the key won't turn, the transponder chip in the key fob may be faulty; it's not sending the security code to the immobiliser.

How do you fix an immobiliser malfunction?

A transponder relies on a battery which may need replacing. You can replace it yourself, being careful to avoid accidentally damaging the transponder chip. If this fails, you should contact your dealership because the problem could be the transponder.

If you happen to lose your key fob or the transponder chip, your only option will be getting a replacement from the dealership, which is expensive. On rare occasions, the issue may be the immobiliser system in the vehicle. The problem may be corroded or damaged wires, a faulty ECU, or it's sensors. This would also warrant a call to your dealership or auto repair shop specialising in car electrical systems.

For your car part needs, or informative articles like this, you may refer to Carpart.com.au! It’s your one-stop automotive website, not only for news and how-to articles, but also for buying and selling auto parts, accessories, and even entire vehicles!

By Eric Anyega