Why Won't My Key Fob Work?

Why has my car key fob stopped working

A car key fob is a small radio transmitter with a battery, buttons, a circuit board and a chip inside a plastic shell. Any one of those parts can fail, and each failure looks slightly different. The diagnosis ladder below puts them in the order worth checking, so you start with the cheap and simple cause and only move on when it is ruled out.

Car key fob battery: the first thing to check

Start with the battery. A coin battery in a key fob lasts a long time, and it fades gradually, so the first sign is a fob that works only when you stand close to the car, or a fob that needs two or three presses before the doors respond. A battery that has gone flat altogether gives no response at all.

Changing the battery is a legitimate owner task, and it is worth trying before you call anyone. Find the correct coin battery for your fob, using the vehicle handbook or the markings on the old battery, and fit it the same way up as the one you remove. Open the case gently at the seam, and never force it: a cracked case can damage the buttons or the chip inside. Test the buttons near the car once the case is closed.

If a new battery fixes the fob, the job is done. If the fob still does not work, the fault sits beyond the battery, and the next steps on the ladder are the ones to work through. Do not keep buying batteries: one fresh battery is enough to rule the battery out.

Worn car key fob buttons and damaged car key fob shells

Buttons wear out from use. The lock button is pressed far more often than the boot button, so it fails first. If one button has stopped working while the others still respond, the button itself is the likely fault, not the battery and not the chip. A button that needs a hard press, or a button that works only when pressed at an angle, points the same way.

The shell matters too. A fob that has been dropped can crack, and a cracked shell lets the buttons sit badly, so they do not press the contacts underneath. A shell that has come apart can also let moisture in, which damages the circuit board. A new shell and a new set of buttons can put a fob right when the electronics inside are still sound, and that repair is far simpler than replacing the whole fob.

If the case is damaged, stop forcing it. Tape is not a repair, and a fob held together with tape will fail again. The key fob repair and replacement in Solihull service can fit a new shell and new buttons at the car, and test the fob with you before leaving.

Failed car key fob chips and water damage

The chip is the part the car looks for. It holds the code the vehicle expects, and when that code cannot be read the car treats the key as a stranger, so a fresh battery changes nothing. A fob whose chip has failed gives no sign of life at all, even with a new battery fitted.

Water is the most common cause of a failed chip. A fob dropped in a puddle, left in a wet pocket, or put through a washing machine can suffer damage that no battery will fix. Drying the fob out may help if it was a brief splash, but a fob that has been soaked is beyond a home fix. Do not open the fob and touch the circuit board: the board is delicate, and handling it can finish what the water started.

A failed chip means the fob needs replacing rather than repairing. The new fob is cut and programmed to the car at the vehicle, and the old fob can be removed from the memory of the car where the vehicle allows it.

One point of confusion is worth clearing up: a fob that has been dropped can look fine on the outside while the chip inside has cracked. The shell protects the electronics from knocks, but a hard drop onto concrete can still damage the chip or lift the circuit board from its contacts. If the fob stopped working right after a drop, say so on the call: it points the locksmith straight at the chip, and it rules the battery out without a wasted visit.

When a car key fob needs reprogramming

Sometimes the fob is fine and the car has lost the pairing. The fob looks sound, the battery is fresh, the buttons press cleanly, and still the car ignores it. That points to reprogramming: the fob and the immobiliser of the car need to be paired again through the OBD port, so the car recognises the fob as its own. That pairing is car key programming in Solihull, and it is done at the vehicle.

Reprogramming is locksmith work, not an owner task. It needs the right equipment for the make and model, and it needs proof of ownership for car keys, because a programmed key starts the car. Have the V5C logbook and photo ID ready when you call, and tell us the make, model and year of the car.

A fob can also lose its pairing after a flat car battery, or after the car battery has been disconnected for other work. If the fob stopped working right after the car was jump-started or the battery was changed, say so on the call: it points the locksmith at the pairing rather than at the fob itself, and it saves time at the car.

When your car key fob needs a locksmith

Call a car locksmith when a new battery has not fixed the fob, when the case or the buttons are damaged, when the car does not recognise the key at all, or when the fob has been soaked. Those are the signs that the fault sits in the fob or its programming, and forcing the case open will only make it worse.

Call or WhatsApp 07367 634032, 24 hours a day, and describe the fob and what it does when you press the buttons. Tell us the make, model and year of the car, and whether any key still works. We will tell you plainly whether the fob can be repaired or whether it needs replacing, and we will give you a clear quote before we travel. Full details are on the contact Car Locksmith Solihull page, and car key replacement in Solihull covers a new key from the start.

• Thatcham Research on vehicle security
• Sold Secure on lock and key security