Car Immobilizer Problems: 5 Common Issues & Solutions

New cars have an immobilizer that is a great security system. It will prevent thieves from unlocking and taking your car. On the flip side, it can prevent you from safely using your car if it has an issue.

Many different issues can cause the immobilizer to stop working, so we’ve put together the most common issues and their solutions to keep your car from locking you out by mistake.

#1 – Your Car Illuminates The Key Symbol In The Gauges

Most car owners don’t realize there is a key symbol in their gauge cluster to indicate the immobilizer has a problem.

The more common light that shows up is the Check Engine Light (CEL) which indicates a trouble code for the engine or a related system.

When the key symbol illuminates, consider it a potential problem that could leave you stranded.

How to Fix It

When you initially start your car, the gauges cycle through the diagnostic lights. If the immobilizer system detects a problem, the key symbol will flash for 2-3 seconds.

Most of the time the key and immobilizer reconcile the problem and the light will stop flashing.

In some cases, there is a definite miscommunication or lack of communication between the immobilizer system and the transponder key. When that happens, the key symbol will stay illuminated.

There are two potential paths to take to resolve this issue.

The key fob has a battery inside the housing that emits a signal to the immobilizer system. The battery could be close to dead in the key fob and not sending the required signal to pair with the immobilizer.

If your key fob requires you to be closer to the car than previously, the battery needs to be replaced.

If the key fob isn’t the cause, the immobilizer system is to blame. Aftermarket electronics can block the signal emitting from the key fob. If you recently had something new added to your car, it may be the source of the problem.

The immobilizer can also lose connection to the key fob if you have had the car battery replaced or there has been a disruption to the Body Control Module (BCM) in the car. If it loses its programming, it can be reprogrammed to connect the key fob to the immobilizer system.

#2 – Your Car Has Trouble Starting Or Staying Running

The key transponder and the immobilizer system work together to prevent theft of your vehicle. Your key fob may allow you in the car, but the immobilizer can prevent your car from starting or running longer than a few seconds.

How to Fix It

New cars have a transponder chip that emits a coded signal to your immobilizer system to prove that they are registered to work together.

If a key with an unregistered code tries to start the car, the immobilizer system is designed to prevent the car from starting or running for very long as a theft deterrent.

If your car shows the key symbol in the gauges, the immobilizer system doesn’t recognize the key being used or the system has identified another problem.

One way to rule out the key as the issue is to try another key that is programmed to the car. Most new cars come with two keys. If one key doesn’t work, try the other one to know if it truly is just one key causing the no-start condition.

If both keys cause the same problem, the immobilizer system doesn’t recognize the transponder chip in either key. Both need to be reprogrammed and paired to the car, and the problem should be resolved.

If they can’t be programmed to the car, the immobilizer module should be replaced.

#3 – You Can’t Lock or Unlock Your Car

Many new cars have the option of a physical key to unlock the driver’s door, but some newer cars are strictly electric for locking and unlocking the doors.

If your car requires a key fob to operate the locks, you may be stuck outside your car with no way to get in if the immobilizer system has a problem.

How to Fix It

Older cars have physical keys for the door locks and the ignition cylinder, but more and more cars are moving away from keys to just key fobs with transponder chips paired to the immobilizer system.

Physical keys will still unlock and lock the driver’s door if it has a key cylinder around the door handle, but that may not be enough to start the car.

If you’re unsure of where the key is, you need to read through the owner’s manual for your car. The key may be inside the key fob, and you just need to know how to release the key.

If your car uses an Intelligent Key (I-Key) it may have a push-start button instead of a key cylinder. This requires the immobilizer to recognize the transponder chip to start the car.

Always check the key fob battery as a potential problem as they can prevent the I-Key from working. Batteries are relatively cheap to replace. You can try a second key fob for the car to prove the first is or is not the problem for the no-start condition.

If neither key fob works and the batteries are good, then the key fobs should be reprogrammed to the car. If they can’t be programmed to your car, the immobilizer system has a problem, and it should be repaired or replaced.

#4 – Your Car Alarm Doesn’t Work Correctly

Your car has a built-in alarm system that should prevent your car from being stolen and make a lot of noise to attract attention.

If the immobilizer system isn’t working, your car alarm may go off when you open the door, or it may never go off even if there is a real problem.

How to Fix It

This issue can have two different problems depending on the symptoms. If your immobilizer recognizes the transponder chip in your key fob, it shouldn’t sound the alarm.

If the alarm frequently goes off, the car doesn’t recognize the key. You can have it reprogrammed to the car or try a secondary key fob.

If the second key fob doesn’t work either, the immobilizer has lost its programming and should be reprogrammed or replaced.

If the car alarm never goes off, the immobilizer system needs to be investigated.

Some car models have the option to turn off the alarm completely, and you may have turned it off by accident. Many times turning the alarm off and on can be done with the ignition turned on and a select few buttons pressed in sequence.

Check your owner’s manual for the proper sequence. If the alarm is on and it doesn’t work, the immobilizer module may need to be replaced.

#5 – Your Key Doesn’t Allow the Ignition To Turn On

The immobilizer system controls a physical lock in the steering column that prevents the ignition cylinder from turning.

If the transponder chip in the key or the key fob doesn’t allow the ignition to turn on, the immobilizer is preventing your car from starting.

How to Fix It

The correct key for your car will work in the door lock and ignition cylinder, but the transponder chip isn’t recognized by the immobilizer system. Check the battery in the key fob as it may lose power and prevent your car from recognizing the correct key.

Another possibility is that the transponder chip key has been damaged from being dropped or exposed to moisture. Try a second key or key fob if you have one to know if the first one is the problem.

If both keys exhibit the same issue, the immobilizer system should be reprogrammed to both keys. If that isn’t possible, the system should be replaced.

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