In short
- A used car should come with at least two working keys; replacing a lost coded key can be a genuinely large bill.
- The immobiliser must recognise the key every time - intermittent no-starts are often a failing immobiliser or worn key.
- Central locking, the boot release and the alarm should all work from each key, as these repairs add up quickly.
- Our inspection in Budapest confirms every supplied key works fully and that the security systems operate as they should.
Keys and security are among the most overlooked parts of a used-car purchase, right up until they become an unexpected bill. A modern car key is not a piece of cut metal but a coded electronic device paired to the car, and replacing a missing one can cost far more than buyers imagine. Meanwhile a failing immobiliser can leave you stranded with a car that cranks but will not start, and faulty central locking or an over-sensitive alarm are irritating and not always cheap to cure. This guide explains what a pre purchase inspection checks on a used car's keys, immobiliser and locking, and why two working keys in your hand is worth more than it might first appear.
Why the number of keys matters
A used car should ideally be supplied with at least two working keys. This is partly convenience and partly protection: keys are lost, and if a car comes with only one, you are one mishap away from a replacement that, on many modern cars, involves ordering a coded key, having it cut to the car and programming it to the immobiliser. Depending on the make, that can be a substantial and inconvenient expense.
A missing key can also, occasionally, hint at history. A car sold with a single key may simply have lost the spare, but it is worth understanding why, particularly on a car whose provenance is otherwise unclear. During an inspection we confirm how many keys are supplied and that each one performs every function, because discovering after purchase that the second key does not lock the car or start the engine is a common and avoidable annoyance.
The immobiliser and intermittent no-starts
The immobiliser is the anti-theft system that only allows the engine to start when it recognises the correct coded key. When it works, it is invisible; when it begins to fail, it produces one of the more frustrating faults on a used car - an intermittent no-start where the engine cranks but will not fire, often with a security light flashing on the dashboard.
The causes range from a worn key transponder or a failing receiver ring around the ignition to a fault in the immobiliser module itself. A worn key is cheap to address; a module fault is not. Because the problem is intermittent, it can easily be absent during a short viewing and appear a week after purchase, which is why we look for stored faults and test starting with each supplied key rather than relying on a single successful start.
Central locking, boot release and the alarm
Central locking seems trivial until a door or the boot stops responding, at which point the repair can involve a failed actuator hidden inside the door, wiring that has fatigued in the flexible loom between door and body, or a fault in a control module. These are common on older cars and, individually minor, can add up when several actuators are worn at once.
Testing every door and the boot
We operate the locking from each key and from any interior switch, checking that every door, the boot or tailgate, and the fuel flap where electrically operated all respond. A single lazy actuator is a modest repair, but a car where several are failing points to age-related wear that will keep generating bills.
The alarm and its quirks
An alarm that triggers without cause, or that will not set, is both irritating and a sign of a sensor or wiring fault. On some cars a failing alarm siren has its own small battery that degrades and causes false triggers. We note whether the alarm arms and disarms cleanly and whether any warning suggests a fault in the security system.
Comfort and convenience electronics that ride along
Keys increasingly do more than lock and start. Keyless entry and go, remote boot opening, folding mirrors on locking and memory functions tied to a particular key or fob are all conveniences that can fail, and on some cars a keyless system introduces its own security and battery-drain considerations. A key fob with a flat battery can also masquerade as a more serious fault, so establishing the simple causes first is part of a sensible check.
None of these are reasons in themselves to avoid a car, but they are worth confirming so the price reflects reality. A car advertised with keyless entry and two keys should deliver exactly that, and a buyer should not discover after handing over the money that one key is a basic blank that will not operate the convenience features.
Fob batteries, keyless theft and everyday security
Before assuming the worst about a key that behaves oddly, the simple causes are worth ruling out. A key fob with a flat internal battery can fail to lock the car or trigger keyless entry, mimicking a more serious fault, and it is a trivial and cheap thing to put right. Establishing whether a misbehaving key is simply flat, rather than faulty, saves both worry and money.
Keyless entry and start, convenient as it is, carries its own security considerations on the used market. Some keyless systems have been vulnerable to relay theft, where the signal from a key left near the front door is captured and repeated. It is worth knowing whether a car has keyless entry and whether the maker offers a fob that can be switched off or shielded. A working mechanical steering lock and any factory immobiliser add further, welcome layers.
How we check a used car's keys and security in Budapest
Our inspection confirms how many keys come with the car and tests each one fully: locking and unlocking every door and the boot, starting the engine, and operating any keyless or convenience functions. We watch for the immobiliser and security lights behaving correctly, and we read the fault memory for stored immobiliser or central-locking faults that a single successful start would not reveal.
For a buyer, this turns a set of easily overlooked details into a clear line in the report. Knowing that the car comes with two fully working keys, a healthy immobiliser and locking that operates on every door removes a category of unwelcome little surprises - and, where a spare key is missing or an actuator is failing, gives you a concrete point to raise on price before you commit.
Cars we inspect related to this guide
Browsing one of these? Open its inspection page to see the model-specific checks and book an on-the-spot pre purchase inspection in Budapest.
Frequently asked questions
How many keys should a used car come with?
Ideally at least two fully working keys. Keys are easily lost, and replacing a coded key on a modern car can be expensive because it must be cut to the car and programmed to the immobiliser. A car supplied with only one key is not a reason to walk away, but it is a fair point to raise on price, and we confirm that every supplied key performs all its functions during the inspection.
What causes an intermittent no-start on a used car?
A common cause is the immobiliser failing to recognise the key - perhaps a worn transponder in the key, a failing receiver around the ignition, or a fault in the immobiliser module - which leaves the engine cranking but not firing, often with a flashing security light. Because it is intermittent, it can be absent during a viewing and appear later. We test starting with each key and read the fault memory to catch it.
Is it expensive to replace a lost car key?
It can be, especially on premium and newer cars, because a modern key is a coded electronic device that must be ordered for the specific car, cut and then programmed to the immobiliser. Costs vary widely by make and model. This is precisely why we confirm the car comes with a spare working key, so you are not facing that expense shortly after purchase.
Why is central locking so often faulty on older cars?
Because each door and the boot has its own lock actuator, and the wiring flexes every time the door opens and closes, both of which wear with age. A single failed actuator is a modest repair, but several failing at once signals age-related wear that will keep generating bills. We test the locking from every key and switch so you know the true state before you buy.
Is a car with keyless entry less secure to own?
Some keyless systems have been vulnerable to relay theft, where thieves capture and repeat the signal from a key left near the front door. It is not a reason to avoid keyless cars, but it is worth knowing whether the fob can be switched off or shielded, and keeping it away from the door at home. We confirm which entry system a car uses so you can judge the everyday security for yourself.
Found the car? Get it checked.
Before you pay, book an independent, English-speaking inspection in Budapest. We come to the car and report in English - 35 999 Ft or 39 999 Ft with photos and video.
