What’s the Meaning of an Immobilizer?

Aside from being a means of transportation, vehicles are also assets that are worth a lot of money. To prevent them from being stolen, car manufacturers have installed a device called an immobilizer.

What Is an Immobilizer in a Car?

Immobilizer systems first appeared in the early 1990s in Europe and reduced car theft by nearly 80 percent. Also referred to as “passive anti-theft,” this system is primarily in place to prevent the car from being stolen rather than to prevent somebody from breaking into the car, which is referred to as “perimeter anti theft.”

Pro Tip: Perimeter anti-theft sounds an alarm, but OEM systems won’t sound if somebody breaks the vehicle’s door glass and doesn’t open the vehicle door.

An engine immobilizer is an electronic device present in most modern vehicles that deter vehicle theft. A vehicle engine starts when the driver turns a key that completes a circuit that connects the battery and starter motor. Hot-wiring a vehicle typically bypasses the ignition switch and starts the vehicle without a key.

However, an immobilizer adds an extra layer of security by verifying whether the correct key has actually been inserted into the ignition switch. If the immobilizer doesn’t detect the correct key, then the engine might start, but it will eventually die after a few seconds. Alternatively, it might not crank at all.

Vehicles without an immobilizer can be hot-wired, which means thieves can bypass the ignition switch and turn on the vehicle without a key. Such was the case in 2022 when a trend called the Kia Challenge went viral on TikTok. The videos showcased thieves easily stealing Kia and Hyundai vehicles that didn’t have immobilizers. Since immobilizers have been installed in vehicles, car theft has been greatly reduced.

What Does an Immobilizer Warning Light Mean?

You might be wondering, what does the car-with-key symbol on the dashboard mean? This is most likely the immobilizer warning light, but its appearance can vary depending on the vehicle. Some vehicles have a simple red LED on top of the dash while others may have a “theft” light. Still others may have various different symbols like a car and a key symbol or a car and lock.

The meaning of the immobilizer warning light can also vary depending on the vehicle. The immobilizer light will illuminate as soon as the key is turned into the on position. If the immobilizer detects that the correct key has been inserted, then the light will shut off once the engine has been started. However, the light will blink if the system doesn’t detect the right chip code in the key, which can lead to the engine either not spinning at all (starter disabled) or the engine may start and immediately die.

If this is the case, then you should have it checked at the dealership. Problems with the immobilizer can cause issues such as locking and unlocking issues, as well as being unable to start your vehicle.

Immobilizer systems technically do not require the key or fob to have a good battery, although some require the fob to be placed in a cavity or require it to be used to push the “start” button if the fob battery is weak.

Immobilizer systems technically do not require the key or fob to have a good battery, although some require the fob to be placed in a cavity or require it to be used to push the “start” button if the fob battery is weak.

Richard McCuistian, ASE Certified Master Automobile Technician

How Does an Immobilizer Work?

An immobilizer works by checking the transponder chip found in key fobs and keys. This does not require a battery in the fob or key.

The chip sends a passcode to the vehicle’s immobilizer unit, which may be built into the PCM, BCM, instrument cluster, smart junction box, or a standalone module. The unit verifies whether the passcode is correct before it starts the vehicle. If the incorrect key is used, then the immobilizer may trigger the vehicle’s alarm, though it usually just locks out the starter or the engine will start-and-die. Some newer vehicles will even notify a security service that’ll contact the owner.

Some companies have upgraded their immobilizers to a two-tier security system with a fixed code and a changeable code. The second code is stored in the transponder and is changed every time the vehicle is started. When the driver starts the vehicle, the immobilizer first verifies the permanent code, then requests the second changeable code. The computer compares it to its database and starts the car if it’s correct. The automobile won’t start unless the second code is entered.

Driving With an Illuminated Immobilizer Warning Light

If the immobilizer warning light is turned on and you’ve been able to start your vehicle, then it might have one of the following issues:

• Your key fob is low or has run out of battery. Check the owner’s manual on this.
• Your key’s immobilizer chip is faulty.
• The car battery has recently gone flat (note, however, that this is almost never a problem for the immobilizer).
• Issues with the vehicle’s locking system.

This warning light typically illuminates only when the key isn’t recognized, so you shouldn’t be concerned if it illuminates while you’re already driving. However, a glowing security light might indicate that your vehicle doesn’t trust the key you’re using.

The immobilizer security system could have been activated as a result of an attempted theft, but if it turns on while you’re driving it’s usually due to a battery problem.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Typically, if a vehicle immobilizer system has prevented the vehicle from starting, a B code (ex. B1601) will be stored.

If your security light is on and you can’t start your car, try another key if you have one. Most of the time, the security light indicates that the automobile no longer recognizes the key you’re using, and you might be able to reset the system by using a different key. If your vehicle still refuses to start, then you should seek the help of a professional mechanic.