Key Fob Remote Not Working? Here's Why, and What to Do About It

Electronics have formed a growing proportion of your car’s systems for decades. Starting out as largely invisible components in engine, braking, and stability control systems, the electronic content of the latest vehicles extends to the very complex infotainment systems and driver-assistance functions that we take for granted today. Even the humble ignition key has been replaced in most contemporary vehicles by a wireless starting system, generally known as a smart key.

Unlike the physical keys of yore, today’s smart keys do not fit into a matching lock. You do not turn them to open and start your car. Instead, a radio frequency signal from a remote device does all the work. It’s easy to use and generally trouble-free. But when your smart key system fails, you may be unable to get into and start your car. That’s a major headache.

There can be many reasons why your vehicle’s smart key system is not working. Fixing it can be somewhere between very simple and extremely complex. Once you understand how your smart key system works and how to fix it, you can be back on the road, with you in command of your vehicle once more.

Here’s our guide to smart key problems, their causes, and how to fix them.

First, a brief history…

One of the first keyless entry systems was introduced on several higher-end Ford and Lincoln vehicles in 1980. These early systems allowed you to enter a code on a keypad placed near the door, which unlocked it and permitted you to enter. In the late 1990s, Mercedes-Benz vehicles offered a system called Passive Start and Entry System, which used a fob that generated an electronic radio frequency signal that worked over a short range to unlock the doors and start the car. These systems became popular and spread over time to most cars on the market, as consumers demanded this extra level of convenience. Today, nearly every new car sold has a keyless entry and push-button starting system, controlled by a smart key.

How your smart key works

Your smart key system consists of two primary components: a transmitter and a receiver. The transmitter is built into the fob that you can carry in your pocket or purse when you need to use your vehicle. As the transmitter gets near to your car, its short-range signal can be picked up by the receivers placed both inside and outside your car. The external antennas are used by the door locks to permit you to unlock the doors as you approach. The internal antenna enables the ignition once that the key is inside the vehicle. All you have to do to start the vehicle is push the start/stop button – no physical key is needed.

When you arrive at your destination, simply push the start/stop button to shut the car off, and then lock the doors once you are outside the vehicle. For added security, these radio frequencies are coded for each individual vehicle, which prevents other cars’ fobs from being used to open and your vehicle.

Reasons your smart key system isn't working

Let’s start with the most common problems that could be affecting your smart key system as a whole, followed by some more unusual issues that can cause your smart key system to malfunction.

Let’s first rule out human error:

Before we get into specific problems and fixes, let’s eliminate some possible self-inflicted issues:

1. Are you using the wrong key? (If you have more than one vehicle with a smart key system)
2. Did you leave your transmission in Drive or Reverse? (You need to be in Park or Neutral to start the car)
3. If it’s a cold day, is the fob warm? (Its operation can be affected by the cold)

RepairPal Tip 1: Before you do anything else, try opening and starting your car with the second fob that came with it. If you are like most drivers, you probably use one of your fobs all the time, while the second fob that came with the car sits in a drawer unused. The second, less-used fob will normally be in better condition, with a battery that has more of a charge. If doing this solves your problem, you are good to go – just fix whatever’s wrong with the primary fob right away so you will still have a backup! Keep reading for possible solutions.

RepairPal Tip 2: Also keep in mind that when your smart key system fails, you will likely not be able to open the doors. This will prevent you from getting inside to try starting the car, checking things inside like the fuses, or even accessing the hood release to check the car battery if necessary. To bypass the electronic system, use the physical key that is built into the car’s fob. It will allow you to open the doors. Check your owner’s manual for instructions on removing the key from the fob, as well as accessing the door locks if they are hidden behind removable access panels.

Fob issues

Dead fob battery: This is the most common reason why your smart key system has stopped working. The transmitter in your fob is usually powered by a coin-shaped lithium battery that lasts a long time – but not forever. After a few years, the battery gradually loses its charge, to the point where it may not have enough energy to send its signal to the receiver in your car. You may have previously noticed that the fob’s range was reduced, or it may have taken several tries to make it work. When that fob battery fails, you can’t unlock your doors or start the car.

Possible quick fix to get you going: Use the physical key to open the car door. Try starting the car using the inductive backup system, which is possible in some vehicles. This is done by first closing the car doors and then pushing the fob directly against the start button and depressing it. This should start the car.

Long-term solution: Replace the battery. This usually involves a few simple steps. Search online for “Replacing (your car’s year, make, and model) key fob battery” to find several YouTube videos that will take you through the process, step by step. Remove the old battery, insert the new one, and you’re good to go! If this does not work, keep reading…

Damaged/broken fob mechanism: If replacing the battery did not help, this may be the cause. Your smart key transmitter fob tends to get a lot of abuse while in your possession. It gets dropped, banged around, and exposed to heat and cold on a daily basis. Inside the fob is an integrated circuit board that can be damaged or destroyed with enough hard usage. The battery contacts inside are also somewhat delicate and can be bent or broken. In addition, the fob contains moving parts like the buttons you can push to lock and unlock the vehicle. Any damage to the fob can result in its signals not being sent to the receivers in your car. When this happens, you can neither open nor start your car with it.

Solution: Open the fob, remove the battery for a better view, and look for obvious signs of damage: cracks in the circuit board, teeny electronic components not completely attached to the circuit board, buttons that are loose or out of position, bent or oxidized battery contacts. If you spot any damage (or even if you don’t), you may need to replace the fob and have it programmed for your car. Call your mechanic for suggestions on the most cost-effective and convenient way to get this done.

Fob needs to be reprogrammed: Your smart key system depends on the transmitter in your fob being recognized by the receiver in your car, every single time that it is used. The programming in these devices is designed to have them recognize each other without fail, using a code that is unique to your vehicle. Depending on your specific vehicle, you may need to program or reprogram your fob when the car battery is disconnected or replaced, when a new fob is purchased, or even when you replace a dead battery in your existing remote.

Solution: You may be able to reprogram your fob for the purpose of locking and unlocking your car. After installing a fresh battery in your fob, check your owner’s manual for instructions, or contact your mechanic if the manual doesn’t help. Reprogramming your fob yourself for starting your car may not be possible, due to the car’s immobilizer function and other security concerns. This may require the help of your mechanic or an automotive locksmith. If all else fails, you may have to visit the service department of your brand’s new-car dealership.

Receiver issues

Damaged receiver: The signal sent by your fob must be received by a radio frequency receiver inside the vehicle. If the receiver is bad, the fob’s signal will be unable to open or start the car.

Solution: Try placing the fob right next to the outside door handle and try to open it. If this does not work on either front door, contact your mechanic. Your receiver may be to blame. If your car is still under warranty, the dealer may be able fix it for free – but check the fine print first!

Radio interference: Because your smart key system uses a low-power, short-range signal, it can be blocked by the much stronger radio frequencies from many different sources, including:

• Your cellphone sitting in the console
• The Wi-Fi hotspot in your car or phone
• A Wi-Fi router in a nearby building
• Cellphone towers
• Two-way radios
• Home alarm systems
• Radio stations
• Airports
• Military bases

Solution: If you can’t open or lock your car, use the physical key. Put your phone in the backseat and turn off your Wi-Fi hotspot. Try starting your car by pushing the fob against the start button. If your car still won’t start, contact your mechanic.

Car battery issues

Dead car battery: If you have no electrical power flowing to your smart key system, it will not let you open your doors or get your car started. If nothing else in the car works, you could have a dead battery.

Solution: Use the physical key to open the car door. Verify whether your vehicle has power – the interior lights should come on when you open the door. Call your mechanic, auto club, or roadside assistance to have your car’s battery and charging system checked. Replace the battery if necessary.

Fuse issues

Blown fuse: As with many of your car’s electrically-powered systems, the smart key circuit incorporates a fuse. This fuse will blow in the event that its circuit is overloaded, shorts out, or has some other problem. The fuse basically gives its “life” to prevent serious damage to the smart key system.

Solution: First check your owner’s manual for the location of your vehicle’s fuse box. Next, determine the location of the smart key or start button fuse within the fuse box, as well as the proper rating of that fuse. With the car shut off, open the fuse box and remove the fuse (use the small plastic tweezers or other tool for this task if one is provided). Now check the fuse and see if the wire inside it is broken. Also check that the fuse has the correct rating, according to the information in the owner’s manual.

If a fuse is blown, replace it with a new one of the correct rating (never install a fuse of a higher or lower rating). Close everything up, start the car, and see whether the smart key system now operates. If it does, you have fixed it! If it still won’t work or a new fuse blows again, you may have a more serious problem that requires your mechanic’s attention.

Do you have a phone app that will unlock and start your car?

Many newer cars offer a phone app which provides many different functions. Most of them will allow you to remotely unlock and start your car, using a combination of cellular and satellite technology. If your car is so equipped, try using it to bypass the problem with your smart key system. If the app will let you get into the car and start it, you are in luck! Drive your car to your mechanic right away and have the system repaired.

Can I drive with a bad smart key?

In most cases, no. A locked car that won’t start is not going to do you much good. You may be able to use the phone app mentioned above to bypass the system temporarily, but remember that it will not work in areas with poor cell service and/or satellite reception. It’s best to get your car to your mechanic promptly and have your smart key system returned to normal operation.

Here are some tips to help you avoid the distress of a future smart key failure:

1. Make sure you have a second smart key fob to use as a backup, and bring it with you on longer trips
2. Keep your key fob away from moisture or dirt
3. Be aware of the signs of a low fob battery: reduced range, multiple attempts required
4. Keep extra batteries on hand