Car Key Not Working? How to Open and Start Your Car Again

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Your car key is not working: the buttons no longer lock the doors, or your keyless car does not recognise you. Most of the time, the key’s battery is flat.

No need to panic. The emergency key hidden inside the fob lets you open the car, and often start it, with no battery at all.

Common symptoms and causes

• No button responds: flat battery, wrong battery type or battery fitted the wrong way round.
• The key stopped working after a battery change: battery not seated properly, dirty contacts or, on some models, a key that needs resyncing.
• The car beeps but the lights do not flash when you lock it: a door or the trunk is not fully closed.
• The buttons do nothing while the engine is running: that is normal, the remote is inactive with the ignition on.
• The key works only now and then: radio interference nearby, or a fob damaged by a drop, moisture or heat.
• Neither the key nor the spare opens the car: the car’s 12 V battery may be flat.

A keyless (hands-free) key opens and starts the car without pressing a button as long as it is on you. Skoda calls it KESSY, Renault talks about a hands-free card.

Before you start

• Keep the vehicle manual handy: the location of the emergency key and the start procedure vary by model.
• Find the metal emergency blade hidden in the key fob.
• Read the battery type, printed on the old battery or on the cover, for example CR2032.
• Get a small flat screwdriver and, if you have it, the spare key.

Warning: keep button cell batteries away from children, new or used. A swallowed battery causes serious internal burns within hours: call your local emergency number (911 in the US, 999 in the UK, 112 in the EU) right away. Do not throw the old battery in the trash, take it to a collection point or to the dealer.

Warning: opening the fob can damage it and void the warranty, so check the warranty end date first. A new key or a reset is done at the brand’s dealer, never by reprogramming the immobiliser yourself.

Solution 1: open the car with the emergency key and start it

To open the car without the remote:

1. Slide the metal emergency blade out of the key fob.
2. Find the driver’s door lock. On every Skoda, it is hidden under a cap.
3. Insert the blade in the lock and turn it to open the door.

The driver’s door opens. On a Renault with a hands-free card, locking, opening and starting remain possible with a flat card battery; the exact steps are in the model’s manual.

To start a keyless car whose key has no battery left:

1. Look in the manual for the backup spot designed for the key.
2. On an older keyless Skoda, hold the key against the start button, then press the button.
3. On a recent Skoda, put the key in the cup holder, then press the start button.
4. On a Renault, place the card where the manual shows, then start the car.

The engine starts. On a Skoda, the key’s coil works without a battery: that is what makes this start possible.

Good to know: on a hybrid Toyota, according to the US manual excerpts we read, the mechanical blade does not start the hybrid system. Follow the manual for your model.

Tip: on a Renault, the dashboard message Pile carte faible (low card battery) warns that the battery is nearly dead. Replace it as soon as it appears, before you are stranded.

Solution 2: replace the key battery correctly

1. Read the battery type and orientation, printed on the cover or on the old battery.
2. Buy a battery of the same type: on a Kia, a different type can make the key misbehave.
3. Open the fob at its slot with a small flat screwdriver.
4. Remove the old battery.
5. Check that the new battery has no ink marks on it.
6. Fit the new battery the right way round, following the polarity engraved on the cover.
7. Close the fob until it clicks, then refit the screw if there is one.

The buttons lock and open the car again. While you work, do not touch the circuit board attached to the cover.

Tip: take a photo of the battery before removing it. You can then check the new battery’s orientation at a glance.

The battery type is printed on the old cell. Here are two common coin battery types, to pick according to your key.

On a Renault hands-free card, the method is different:

1. Slide the rear shell down while pressing zone A.
2. Lift the battery cover at zone B.
3. Press one side of the battery and lift it out.
4. Insert the new battery, matching the polarity.
5. Reassemble the card and check that the cover is clipped in place.
6. Near the car, press a button on the card 4 times.

The card controls the car again, and the Pile carte faible message clears at the next start. For model-by-model details, see how to change a Renault key battery.

Good to know: on a Kia key, detach the mechanical key first, then pry off the cover. The battery is a 3 V CR2032. If in doubt, have the dealer change it.

Solution 3: rule out the 12 V battery and interference

1. Close all doors and the trunk fully: a beep without a flash means something is not shut properly.
2. Switch off the engine and the ignition: with the ignition on, the remote buttons are inactive.
3. Try again somewhere else, away from any source of radio interference you suspect.
4. Try the vehicle’s spare key.

If the spare key works, the first key is probably at fault. If no key opens the car, suspect the 12 V battery: on a Skoda, the car no longer opens when it is flat.

1. Open the driver’s door with the emergency blade.
2. Recharge the vehicle’s 12 V battery.

Once the battery is recharged, the keys control the car again. For charging or jump-starting, see dead car battery: what to do to restart.

If the 12 V battery is the culprit, here are two devices to recharge it or to jump-start without another vehicle.

Heat, cold, moisture and drops damage the fob’s electronics. Store the key somewhere safe.

Solution 4: car key not working after a battery change

1. Reopen the fob and check that the battery is the right type.
2. Check that it is the right way round and sits firmly against the contacts.
3. On a Renault hands-free card, go near the car and press a button on the card 4 times.
4. Look in the manual for a resync procedure: when one exists, it depends on the model.

The key responds again. If it does not on a Renault, the manual provides no user resync: replacing or resetting a key or card is done at the dealer.

According to user reports, some older models have a manual procedure. Warning: it resets the car’s keys, and any key you do not program during the procedure stops working. Gather all your keys before you start.

1. On a Clio 2, according to a forum, hold the interior lock button for more than 5 seconds.
2. Then press each key 3 times, within 10 seconds.

Every key included locks and opens the car. On a Peugeot, owners report that a battery change is usually enough, but some keys need the dealer’s tool.

If nothing works

Stop if the key stays dead with a new, correctly fitted battery while the spare key works. The key is then faulty or no longer recognised. Do not try to reprogram the immobiliser yourself.

Contact the brand’s dealer or an automotive locksmith. For Renault, bring the vehicle and all keys or cards, up to 4 per vehicle. Have ready:

• photo ID;
• the vehicle registration document (title or V5C);
• all the vehicle’s keys and cards, including the ones that still work.

Take better care of your car key: our toolbox

Spare batteries, a tool to open the case and a tracker so you never lose the key: here is what helps you look after your car key.

Frequently asked questions

Why is my car key not working after a battery change?

The battery is the usual culprit: wrong type, wrong orientation, poor contact or an ink mark. On a Renault hands-free card, press a button 4 times near the car. If nothing changes, some keys have to go to the dealer.

How do I open my car when the remote does not work?

Use the metal emergency blade hidden in the key. Slide it out of the fob, then open the driver’s door with its lock, sometimes hidden under a cap. Your model’s manual shows where it is.

How do I start a keyless car when the key battery is dead?

Place the key in the backup spot shown in the manual. On a Skoda, hold it against the start button on older models, or put it in the cup holder on recent ones. On a Renault, starting remains possible with a flat card battery.

Do I need to resync a car key after changing the battery?

Not always: it depends on the model, and the manual says so. Renault provides no user resync, only 4 presses of a button on the hands-free card. On other brands, according to owners, a procedure or the dealer’s tool is sometimes needed.

How long does a car key battery last?

About 2 years for a Renault remote, several years for a Kia key. The Toyota manual excerpts we read give 1 to 3 years. Replace it as soon as the dashboard flags a low battery.