When a Car Key Will Not Unlock the Door
A car key does not unlock the door when the remote battery is flat, the battery of the car is flat, the key blade or the door lock is worn, or the lock is blocked by dirt or ice.
Inta-Lock Car Key Guides. Updated October 2026.
Every one of those causes sits in one of three places, the key, the door lock or the car itself. Five checks at the car tell the three apart, and the sign you see at the door names the fault.
A flat car battery silences the remote and leaves the blade as the way in through the driver door. A blade that does not turn is never forced, because a snapped blade adds a second job to the first. Where the checks change nothing, the door is opened by non destructive entry, and what the visit covers is confirmed on the call.
What Do You Check First When the Key Does Not Unlock?
Five checks at the car, in this order, separate a key fault from a door lock fault and a car fault before anything is forced.
- Stand beside the driver door, press the unlock button on the remote and watch the indicators. Lights that flash show that the car has heard the key.
- Try the remote on the other doors and on the boot. One door that stays locked while the rest open points to that door and not to the key.
- Take the mechanical blade out of the remote, where the key carries one, and turn it in the lock of the driver door. On some models the keyhole sits under a cap on the door handle, and the handbook of the car shows it.
- Fetch the spare key and repeat the remote and the blade. A spare that works puts the fault in the first key.
- Look through the glass for a sign of power, an alarm light on the dashboard or a cabin light. A car with no light at all has a flat battery, and the key is not the fault.
A blade that stops or binds in the door lock is left alone at that point.
Which Sign Points to Which Fault?
Each sign at the door points to the key, the door lock or the car itself, and the table sets six signs against the fault behind each one.
| What you see at the car | Where the fault sits | What confirms it | What puts it right |
|---|---|---|---|
| No remote button does anything, and the car still shows a dashboard or cabin light | The key, in the remote battery or the remote electronics | The spare key unlocks the car from its remote | A new remote battery, then repair of the remote where the battery changes nothing |
| Neither key unlocks the car and the car shows no light at all | The car, in its own battery | The blade opens the driver door and the dashboard stays dark | The battery of the car charged or changed. The key is left as it is |
| The remote unlocks every door except one | That one door, in its lock motor or its latch | The same door stays locked from the central locking switch inside the car | Repair of the lock at that door |
| The blade stops before it is fully in the keyhole | The door lock, blocked by dirt, ice or a broken part | The spare blade stops at the same depth | The lock cleared, thawed or repaired |
| The blade goes fully in and does not turn | A worn blade, or a worn or seized door lock | A spare blade that turns names the first blade. A spare that also binds names the lock | A new blade cut for the lock, or the lock repaired |
| The blade turns freely and the door stays shut | The linkage or the latch inside the door | The key turns with no resistance and no sound from the door | The linkage or the latch inside the door repaired |
The table names the place a fault sits, not what the repair costs. A quote is agreed before work begins, so the figure is known before a key or a door lock is touched.
Key in your hand in Leicester or Leicestershire and the door still locked? Matt opens the car by non destructive entry, and a quote is agreed before work begins.
Call Matt on 0116 442 2084Why Does the Remote Stop Unlocking the Door?
The remote stops unlocking the door for one of five reasons, a flat remote battery, damage inside the remote, a lost pairing with the car, radio interference or a fault in the central locking of the car.
- A flat remote battery. The coin battery in the key weakens before it dies. The range shortens first, so the remote works only close to the door, and then the buttons do nothing.
- Damage inside the remote. Water, a drop on a hard floor and years of presses wear the button contacts and the circuit board.
- A lost pairing with the car. The car unlocks only for a remote it has stored. A remote that has lost that pairing sends a signal the car ignores, and a new battery changes nothing.
- Radio interference. Strong radio sources close to the car drown the signal of the key. Vehicle makers list television towers, radio stations, power plants and airports among them. The mechanical blade in the lock of the driver door does not depend on the radio signal.
- The central locking of the car. The receiver, a fuse, the wiring into the door or the lock motor fails on the car side. Both keys then fail in the same way, which is the sign that the remote is sound.
Thatcham Research advises a check that the car has locked after the remote is pressed, by the locking noise and the flash of the lights, as set out in the Thatcham Research car security guidance.
Why Does the Key Blade Not Turn the Door Lock?
The key blade does not turn the door lock when the blade is worn or bent, when the lock is worn, dirty or seized, or when ice holds the parts inside the lock still.
- A worn blade. The cuts of a blade round off with use, and a rounded cut no longer lifts the parts inside the lock to the right height. A copy made from a worn blade carries the same wear.
- A bent or cracked blade. A blade that is bent enters the lock at an angle and binds.
- A worn door lock. The parts inside the lock wear in step with the key. The lock then turns only with a wiggle, and later it does not turn at all.
- A door lock blocked by dirt or corrosion. Dirt and corrosion inside a door lock hold its moving parts. A car opened by remote does not turn its door lock, so a seized lock goes unnoticed until the day the blade is used.
- Ice in the lock. Water inside the lock freezes in cold weather and holds the moving parts. The lock turns again once the ice has thawed. Force on the key does not thaw it.
A blade that does not turn with normal hand pressure is not turned harder. Extra force bends or snaps the blade, and the lock stays as it was.
Does a Flat Car Battery Stop the Key Unlocking the Door?
Yes, a flat car battery stops the remote unlocking the door, because the central locking and the receiver that hears the key both run on the battery of the car.
The remote is not at fault in this case, and a new remote battery changes nothing. Manufacturer handbooks state that a discharged vehicle battery prevents keyless entry from working normally.
The mechanical blade is the way in. Manufacturer handbooks state that the driver door unlocks from outside with the key or the emergency key when the battery of the vehicle is discharged. On some models with an alarm, the alarm sounds as the door opens on the blade and stops once the ignition is switched on.
When Does a Locked Door Become a Job for a Locksmith?
A locked door becomes a job for an auto locksmith when both keys fail, when the blade does not turn without force, or when the blade turns and the door stays shut.
At that point the car is closed to its own key, and the fault is in the door lock or behind it. Inta-Lock opens a car by non destructive entry for a driver locked out of the car, and what the visit covers for the key or the door lock is confirmed on the call.
A quote is agreed before work begins. Matt is with you within the hour in Leicester, and the same day across Leicestershire.
Identity and authority to request the work are checked before the car is opened. The V5C vehicle registration certificate, which names the registered keeper, and photo identification are common examples, and what applies is confirmed on the call.
A child or an animal shut inside the car changes the order of the calls. The police list an immediate danger to life as an emergency on the Police.uk contact page, so that call goes to 999 first and the key fault waits.
Which Related Faults Belong to a Different Repair?
Four situations sit beside the key that does not unlock the door, and each one belongs to a different repair.
How Does a Key Fault Differ From a Door Lock Fault?
A key fault follows the key, while a door lock fault stays with the door. A faulty key fails on the door and the spare key works. A faulty door lock refuses both keys, and the same keys still work the other locks of the car.
The repair differs in the same way. A key fault ends with a key repaired or a new key cut and programmed. A lock fault ends with car door lock repair, where the lock, the latch or the linkage inside the door is put right and the existing keys are kept.
What About Worn Buttons or Water in the Remote?
A remote that fails on one button, works only when squeezed, or stopped after getting wet has a fault in its own electronics. The remote is repaired and the key is kept. That work is key fob repair, which covers the remote electronics, the buttons, the case and the battery.
What Follows When a Fob Is Past Repair?
A fob with a cracked circuit board or heavy corrosion is replaced and not repaired. A new fob is supplied, its blade is cut and the fob is programmed to the car. The steps and the factors that move the figure are set out under replacing a key fob.
What Is the Opposite Fault, a Car Locking Itself?
The opposite fault is a car that locks when nobody asked it to. The keys often end up shut inside. The causes are covered under why a car locks itself automatically.
A car in Leicester that stays locked to its own key is opened by non destructive entry, and the phone is answered 24 hours a day.
Frequently Asked Questions
Why does my key fob not unlock the car after a new battery?
A key fob that does not unlock the car after a new battery has a fault beyond the battery, in the battery contacts, the circuit board, the pairing with the car or the car itself.
A battery fitted the wrong way round or of the wrong type gives the same result. The spare key is the test. A spare that unlocks the car places the fault in the first fob.
Why does my key work in the ignition but not in the door?
A key that works in the ignition but not in the door points to the door lock, because the same blade turns one lock and not the other.
The door lock and the ignition are two separate locks, so wear or dirt in the door lock does not show at the ignition. A car opened by remote does not turn its door lock, and the fault goes unnoticed until the blade is used.
Why does the remote unlock every door except one?
A remote that unlocks every door except one points to a fault at that door, in its lock motor, its wiring or its latch.
The key is sound, since the other doors answer it.
Where is the keyhole on a car with keyless entry?
The keyhole on a car with keyless entry sits on the driver door, and on some models it is hidden under a cap on the door handle.
The mechanical blade stored inside the keyless key fits it. The handbook of the car shows where the cap is and how the blade comes out of the key.
Does cold weather stop a car key unlocking the door?
Yes, cold weather stops a car key unlocking the door when water inside the lock freezes and holds the moving parts still.
The lock turns again once the ice inside it has thawed, and force on the key does not thaw it.
Is it safe to force a key that does not turn in the door?
No, a key forced in a door lock that does not turn bends or snaps, and the broken piece of the blade stays in the lock.
The door then holds a broken key as well as the first fault.
How much does it cost to fix a key that does not unlock the door?
The cost of fixing a key that does not unlock the door depends on where the fault sits, and a quote is agreed before work begins.
A remote battery sits at the low end of the cost. A fob repair, a new key cut and programmed, and a door lock repair each raise the figure, and the key type and the vehicle move it further. No price list is published.