Hyundai Ioniq Won’t Unlock – Somethings flat!

Car problems are never good at any time, but your Hyundai Ioniq won’t unlock well. Don’t panic; I have the solution to open your car.

Reasons your Hyundai Ioniq won’t unlock include:

  • Dead Key Fob
  • Dead 12V Battery
  • Door handle is frozen

In this article, we’ll look at how to open your Hyundai Ioniq and get you going again.


Dead Key Fob

The most common reason that your Hyundai Ioniq won’t unlock is a problem with your key fob. The first thing to check is the distance from the vehicle. This probably sounds obvious, but there is a limit to how far away from the vehicle you can be for the fob to work. It needs to be between 28 – 40 inches from the door handle for auto unlock to work.

If it’s not working even with repeated pressing of the fob, then your fob’s battery is probably dead. There are a couple of options if this is the case:

  • Try another fob
  • Replace the battery
  • Use the mechanical key

Try Another Fob

Trying an alternate fob might be easier said than done. Your fob might be at home, and you’re not, or it might be with someone else, and you have no way of getting it currently.

If you have access to another fob, then try and open your car with it. If it opens, then the battery in the first fob is definitely dead and needs to be replaced. (see below).

If it doesn’t open the car, then the fob is not the problem. It is then the 12V battery that needs to be investigated. (Skip to the next section for 12V battery problems)

Replace the battery

The battery in your fob lasts about 3-4 years. To replace the battery, you need to open the fob. Follow the steps below:

  1. Press the small dot on the button side of your fob
  2. Remove the mechanical key
  3. With a small file or screwdriver, press down on the slot on the right-hand side with the fob facing the button side up.
  4. The case will break into two
  5. The battery is now visible
  6. Remove the old battery
  7. Carefully insert the new battery (CR2032) – widely available in-store and online.
  8. Try to avoid touching the face of the battery
  9. Click the casing back together
  10. Reinsert the mechanical key

Your fob should now unlock/lock your car as normal.

Use the Mechanical Key

You may not have access to a replacement battery, but all is not lost. Thankfully Hyundai has inserted a mechanical key in all fobs (Jun 22). To release the key, you need to press on the small circle at one end of the button side of your fob. The key will release, and you must pull it towards you.

Now that you have the key, where do you put it? I know, right! No keyhole in the door! Well, actually, there is. It’s just hidden. This is either for aesthetics or to deter the would-be thief.

Bending down under the handle, you can see a small rectangle hole. Pull the handle as normal towards you, and as you do, insert the mechanical key into the hole.

Using Mechanical Ioniq Key

This releases a small lever/connection behind the triangle portion of your handle. Gently lever the key towards you. This should release the bottom of the casing. Lift it upwards, and the piece should come away in your hand. Behind it, you should see the keyhole. It doesn’t feel very intuitive and actually feels like you’re breaking something, but you’re not. Go with it.

Put the handle piece somewhere safe.

Your alarm will go off when you unlock the car, so be prepared for the noise. This is because your fob normally immobilizes your alarm.

When you sit in, the alarm will go off as soon as you press the start/stop button, but because your fob is dead, this might not work.

However, even though your fob is dead, it has a chip internally that the car recognizes. Holding the fob to the start/stop power button will power your car on.

It’s actually worth doing this procedure, even if there’s nothing wrong with your fob. If it happens for real, you won’t be so panicked. As I say, I don’t think it feels very natural, and car problems are stressful enough without figuring out how to use your mechanical key. It’s invariably wet, dark, and somewhere far from home. It’s good to have the heads up.

Dead 12V Battery

Every electric car has two batteries. The main high-voltage battery powers the car (drive), and a second 12V traditional battery powers everything else. Some EVs are moving away from the lead acid 12V and replacing them with Lithium Ion batteries. But most are still using the 12V acid, which is cheaper to produce. The Hyundai Ioniq uses the traditional (Jun 22), but the Ioniq 5 has Li-Ion installed.

The 12V powers all the auxiliary items in your car, such as locking and unlocking windows and media. When your car doesn’t unlock, and you’ve ruled out the key fob, there’s a high possibility that your 12V is flat.

This is where your mechanical key again saves the day. Without it, you can’t gain entry to your car or access the 12V. Follow the instructions as before to gain entry with the mechanical key.

If you try to start the car, you will most likely get the dash error ‘Key not Detected.’ Even pressing the power button with the fob won’t work. Your 12V will require a boost.

You can either call roadside assistance and wait for them to get you going. Or, if you have a booster pack or jump cables, you can do it yourself. You can’t jump an EV from another EV. It damages the onboard computers.

So, pull the hood lever. It’s located in the footwell, nearest the driver’s door. It has a small icon of an open hood. Pull it towards you. The hood will lift slightly, and an additional internal latch at the front center of the hood needs to be released. Lift the hood and prop correctly using the rod on the right-hand side.

Once the hood is secure, you can locate the 12V. It is behind the right-hand side headlights as you look at the car. Remove the terminal caps and connect your booster or jump cables in the following order:

  • Red (+) on Ioniq to Red (+) donor
  • Black (-) on the donor to Black (-) on Ioniq

Start the donor (booster) and let it run for a few minutes. Disconnect the cables in the reverse order

  • Black (-) on Ioniq to Black (-) donor
  • Red (+) Donor to Red (+) Ioniq

This allows you to start your Ioniq, which will then begin to charge your 12V from the high voltage.

The high voltage battery in your car monitors your 12V, and when it needs it, it gives it a charge. Well, how can it be flat? It only charges the 12V if your car is running. If you are sitting in your car listening to music, have interior lights on, or have something plugged into the 12V adaptor, but the car is powered off, you’re draining your 12V.

Leaving you in quite a pickle. Remember to power your car on if you’re using anything internally.

Frozen Door Handle

Frozen handles and charge ports could well be part of your routine, depending on where you live. EVs don’t really like extremely hot or cold. Extreme cold leads to not being able to access your car.

If your locks/door handles are frozen, then your fob won’t be able to open them. You can try giving the handle a firm bang with the side of your hand. This hopefully will loosen enough of the ice to open the lock.

If not, you will need a de-icer. Spray the entire handle with a de-icer, which will loosen the ice.

If you don’t have a de-icer, you can try a hair dryer (not always practical or possible). Alternatively, try heating your mechanical key. However, if the handle is frozen, likely, you won’t be able to loosen the part to access the door with the mechanical key.

Once you are inside the car, be sure to completely thaw the car before you set off on your journey.

I’ve covered a few of the other common Hyundai issues which you hopefully won’t experience, but if you do, we have you covered with these posts:

If you are curious about other EV models, check out the EV FAQ category.

John Cunningham

John Cunningham is a technical writer here at He's a Red Seal qualified Auto Service Technician with over twenty-five years experience working on Classic and Modern Cars. He's worked for GM, Jaguar, Land Rover, Volvo, Audi, and VW main dealers.

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