5 Signs Of A Bad Immobilizer Or Transponder Key (& Replacement Cost)

The modern vehicle is packed with safety and anti-theft functions. It used to be that all you need to hotwire a car was a screwdriver, a razor blade, and a little know-how – that’s not the case anymore.

Although it's a great way to watch television, today's car theft requires much more sophisticated technology.

But while those anti-theft features are a nifty feature to keep your car in your driveway, when they stop working, that’s precisely where it can leave you stranded. How do transponder keys and engine immobilizers work? Where are they located and what is the cost of fixing them?

We’ll break down everything you need to know to diagnose and repair these critical components here. First, let’s take a look at the signs to look for:

An immobilizer problem or transponder issue is most obvious if there's a symbol of the key on your dashboard. Your car may become difficult to unlock and lock, which can cause it to alarm randomly.

This is a detailed listing of all five symptoms that indicate a defective transponder or engine immobilizer.

Bad Engine Immobilizer or Traponder Key Signs

1. The key symbol for Dashboard

When there are problems with the immobilizer, your car will have a warning lamp on its dashboard. If the immobilizer is in communication with your key, the light will blink for 2-3 seconds.

The light will stay on if there is a problem either with the immobilizer control or transponder keys.

2. Trouble starting your car?

While locking or unlocking your car is directly related to the key transponder; problems with getting it started may be caused by either the engine immobilizer, or both.

If your transponder or immobilizer keys are defective, it is possible for your vehicle to start but stop working after a few seconds. It is an indication that your immobilizer may be defective.

You can push the start button on a push-start vehicle by using the key fob. Although it may sound absurd, if your problem is due to a dead key fob battery, the vehicle will still start. You’ve also narrowed down the source of your problem, so it’s a win-win!

3. Push Start - Problems unlocking your car

Although the immobilizer doesn't directly interact with the immobilizer, it could be that there is a problem with your whole car key. This will cause problems locking the vehicle and starting it.

One of the first problems you’ll notice there is a problem with the whole transponder key is that you might not be able to unlock your car and neither it will unlock the immobilizer.

While this is becoming more of a concern now that vehicles don’t always have a keyed lock on the door, many vehicles still offer both – you just have to know how to take apart your key fob to access the physical door key.

You can save money by replacing your key fob's battery before calling a locksmith. This battery is only a couple of dollars and could save you tons on your locksmith bill!

RELATED : How to reprogram key fobs yourself at home

4. Push Start: Problems with Locking your Car

Just like you’ll have problems unlocking your car if you have a faulty transponder key, you’ll probably have issues locking it with the key fob too.

Manually locking the doors will still work, but if you don’t have a keyed door lock and your key transponder isn’t working, you won’t be able to get back in!

RELATED: How to Unlock & Start a Car With a Dead Key Fob

5. Continue to Push Start your Car Alarm

The transponder key could be the issue if you open your car door and unlock it only to trigger the alarm. The transponder key may communicate with your car so that you can tell who is in the vehicle.

If someone picks your lock and gains entry, it will sound the alarm and scare them off. Of course, if the transponder isn’t working, the alarm can go off even if you are the right person!

The Transponder Key Function or Engine Immobilizer

Transponder keys and the engine immobilizer work together as anti-theft devices to make sure your car is not stolen. They work in tandem, so if you’re having a problem with one of the components, the other won’t work either.

Each transponder key contains a unique code which it sends to the engine ignition system. When the engine immobilizer gets the right code, it knows that the right person is trying to get into or start the vehicle, and you’re good to go. When the code doesn’t match, the vehicle won’t start, and sometimes it will set off the alarm.

This system is also why it’s crucial to protect your key fob with a signal blocking case. All it takes is someone with a signal spoofer to copy the key fob’s signal, and then it’s just like they have the key to your vehicle.

Locate Engine Immobilizer/Transponder Key Problems

Two components are the engine immobilizer receiver and key transponder. The engine immobilizer receiver is usually located in your vehicle’s steering column, close to the ignition. You will find the transponder keys attached to your key fob.

If you’re driving a vehicle with a push start, the transponder key is part of the electronic key you need to keep with you when you start your car. If you’re driving a vehicle with a non-push start ignition, the transponder key is attached to the back of the physical key that you put into the ignition.

How to Repair Engine Immobilizer/Transponder Key Issues

If you’re having problems with your engine immobilizer or transponder, the first thing you should do is replace the battery in your key fob. This is true only for cars with push-start ignitions, but these issues are much more prevalent with this system.

If that doesn’t fix the problem, you’ll likely need to get a new key from a dealership. If the problem with your vehicle is with the transponder or engine immobilizer, you’re going to need to get it reprogrammed, so you can’t just get a new immobilizer or key and expect everything to work.

While this can be frustrating, it’s a good thing. Otherwise, that’s all thieves would need to do to steal your vehicle.