Why won t my key fob work after i changed the battery

After a long period of using the keyless entry remote of your Toyota, one day, you can’t turn it on.

When a car key remote stops working, most drivers think it’s because of a dead battery and buy a new replacement battery.

However, in some cases, a fresh battery could not help solve the problem, and your key fob is still inactive. So what should you do when the Toyota key fob not working after battery change? 

If you are having the same problem, this article is for you. Getting more understanding about this issue will help you solve it on your own.

We’ll go into details about the function of the key remote control, why a key fob stops working, and how to fix it. Without further ado, let’s dive in.

Toyota Keyless Entry System

Keyless Entry System

Some new Toyota models come with the Toyota keyless entry system, and the key fob is one of the most important parts of this system.

This electronic device works by authentication mechanism through security codes.

Like Token Card, which uses disposable and randomly generated OTPs to make transactions, the key fob also authenticates users in real time.

The device will generate random code snippets, change periodically, and code redemption cycles are usually around 30 – 60 seconds.

Because of the encryption and constant changes in the codes that key fob generates, it is very difficult for anyone to copy the waves of these keys.

Therefore, the safety when using Toyota keyless entry system is highly appreciated by users.

How Does The Key Fob Work?

This system works based on the verification code (ID) matching mechanism between 3 parts of the system: the smart key controller, the fob control device and the vehicle’s central processor.

The central processing unit (CPU) of the SCU controller will be started when the user presses the ignition key.

At this time, the built-in Antenna will compare the confirmation code with the key fob control device.

It should be noted that this reconciliation process only takes place within the range of signal exchange allowed and when the remote key is on.

When it is off, even within the range of the permitted signal exchange, this code matching process cannot occur.

At the end of the verification code comparison process between SCU and the key fob, the driver can turn the lock knob to switch the ignition off or on, unlock the car’s neck, and lock the saddle.

And when the driver turns the ignition knob to the “On” position, the SCU intelligent control unit will send a synchronous ID to the central processor.

The ECM central processor will compare this ID with the code installed and stored in memory. Only when the matching is complete can the engine be started.

The problems of the car key fob not working after replacing battery might derive from a worn-out button, broken key or lock, defective programming, or other electrical issues.

You must find the root cause and then replace or repair that part.

Worn Buttons

The worn-out buttons on your fob may be the culprit behind the key fob not working after changing battery. When the driver presses the buttons, contacts will transmit information to a circuit board.

These contacts may deteriorate over time, or the buttons may be so damaged that they no longer reach the contacts.

The most visible indicator of a battered button is that the cover has disintegrated, and you can see the contact inside. Or you can rely on other contexts to make a guess about the buttons’ conditions.

For instance, with a remote that can’t unlock the drive side doors, yet the lock button does function, you may have a battered button.

In order to detect the problem you are facing, you can test a spare fob you have.

If both keys show similar signals and issues, the cause of your key fob not functioning after a battery replacement is likely not a faded button and contact.

Symptoms:

• The key takes many times and strength to receive signals and start your car.
• Faded icons on the fob.
• Buttons only function when they are pressed in a specific manner.
• One button functions properly, while another does not.

Solutions:

• Change the cover.
• Change the key fob.

Broken Locks

The reasons for a key fob not working after battery replacement may be unrelated to the key fob.

It’s very likely that your car key won’t work because the lock is faulty or worn out. In some circumstances, it’s possible that a piece of the lock has broken.

Since these locks are on the outside of the vehicle, environmental changes and external forces can affect the lock.

This can get trapped by dirt and debris if it is not cleaned regularly. Or the lock may be impaired by an external impact.

To determine whether a damaged lock is the cause of the problem, you can check by pressing the remote to open all the locks.

If some of them can’t open, the key fob isn’t responsible for this malfunction.

Neglecting your car door locks can threaten your safety, as it is a main safety feature of the car. When the doors can’t open properly, you can experience unexpected accidents.

Remember to repair your locks immediately when the damage begins to impact their usability.

Symptoms:

• Some door locks can be opened with a fob, while others cannot.
• The door locks move visibly without getting involved or disengaging.
• Locks do not lock or open with the key or when manipulated directly.

Solutions:

• Go to a car mechanic for fixing 
• Replace car lock 

Deprogramming

With a car remote not working after battery change, it is possible that it was deprogrammed.

Deprogramming is the process of instructing the car’s onboard computer to eliminate all current keys out of its access control list.

If the car key does not work with your vehicle, it is likely that the key has not been programmed or has been erased.

This is a common case when you make extra cheap keys. The remote control must be programmed to communicate with your vehicle.

If you don’t do this, what you can do is unlock your car doors and trunk.

You should go to the manufacturer’s website or look into the car manual to find out whether your vehicle has this feature.

If yes, look for guidelines on key fob programming and try to program it on your own. Still, this process can be challenging as it necessitates the use of professional tools.

Symptoms:

• The spare remote is also inoperable.
• The key fob abruptly stops working.

Solutions:

• Try to reprogram on your own
• Ask a locksmith agency for help
• Contact the manufacturer’s customer service

Damaged Key

A damaged key refers to the harm done to the key fob other than normal wear and tear resulting from impacts of external factors.

Improper handling and maintenance and prolonged use may interfere with the pattern and grooves on the key, affecting its performance.

A damaged key can be the root cause of your key fob can’t unlock your car after you have replaced the battery. Damage might be obvious yet not in every case.

You need to change the faulty key completely. As a result, if you have this problem, you will most likely have to pay a higher replacement cost.

Suppose your problems are solely due to broken housing; you can opt for replacing a part of the key fob to save more.

Symptoms:

• Problems arise as a result of the key being destroyed suddenly.
• The key is clearly broken.
• A spare key works while the main key does not.

Solution:

• Replace the full key fob or faulty parts only

Electrical Issues

In other situations, the key fob doesn’t work after replacing battery due to failures of the car’s electrical system.

When the voltage is weak, the contacts receiving the signal from the key do not work. Therefore, when we press the key, it will no longer work.

If you just had your electrical system removed and installed for maintenance, you should check your electricity in the car again.

Other electrical errors that may occur in conjunction with key fob issues include the car horn no longer working, lights not turning on, and so on.

This is a serious and complicated problem, which goes beyond an automobile locksmith service’s depth.

It is a car mechanic with more knowledge and tools to troubleshoot general electrical issues that can help you deal with them.

Symptoms:

• Other electrical problems are occurring in the vehicle.
• The issues began when the wiring was exposed, accessed, or worked on.

Solutions:

• Reconnect wires.
• Change damaged wires.

Can You Fix A Key Fob Not Working After A Battery Change?

100% YES. We have already included the solution for each cause as above. Check whether your ultimate problem lies with the key fob or the car.

After finding your underlying issue, fix or replace the broken parts.

Conclusion

Now you know why changing a battery can impair your Toyota key fobs. It could be due to the damaged locks, worn-out buttons, or faulty programmin.

When your Toyota key fob not working after battery change, you should first track down the root of the problem, then replace the damaged part.

Do you need to reprogram a key fob after changing the battery?

Why is my car not responding to my key fob?

How do you resync a key fob?