“My key isn’t working” can mean several different faults. A modern car key usually has three parts: a remote that locks and unlocks the doors, a transponder chip that tells the immobiliser the engine may run, and a blade that turns the locks and ignition. Working out which part has stopped working is the quickest way to the right fix.
The remote won’t lock or unlock, but the car starts
If the engine starts normally but the buttons do nothing, the problem is the remote, not the immobiliser. The usual suspects are:
- A flat remote battery. Most remotes use a small coin cell. If the range has been getting shorter for a while, this is the first thing to check.
- Worn buttons or a damaged circuit board. Keys that have been dropped, sat on or put through the wash often fail here.
- The remote has lost its pairing with the car, which can happen after a battery change or a flat car battery on some vehicles.
Try your spare remote. If the spare works, the fault is in the first key. If neither works, the problem is more likely on the car’s side, such as the central locking receiver or a fuse.
The doors open, but the car won’t start
If the key turns but the engine will not start, or starts and dies after a second, and a key or security light flashes on the dashboard, the immobiliser is probably not recognising the transponder chip. Common causes are a chip that has cracked or fallen out of a broken key shell, a key that was never programmed to this car, or a fault with the immobiliser’s reader around the ignition.
A weak car battery can also cause confusing symptoms that look like a key fault, so it is worth ruling that out. If the engine clicks rather than turning over, read our guide to a car that won’t start and just clicks.
The key won’t turn in the ignition or door
A key that will not turn is usually mechanical. The blade may be worn or bent, or the steering lock may be under tension. Gently move the steering wheel left and right while you turn the key. If that does not help, the ignition barrel or lock may be worn.
Never force a key that will not turn. A snapped blade stuck in the ignition turns a simple job into a much bigger one.
Push-to-start: “key not detected”
On keyless cars, a “key not detected” message usually points to a flat fob battery. Most of these vehicles have a backup method, often holding the fob against the start button or placing it in a marked spot, which lets you start the car with a weak fob. Your owner’s manual shows where.
Cheap replacement shells and keys
Replacement key shells and blank keys bought online vary a lot in quality. Moving the electronics into a new shell can work well, but a poorly cut blade can wear the locks, and a chip that does not match the vehicle will not start it no matter how well the blade is cut. If you are unsure, ask before you buy.
Getting it sorted
Tell us the make, model and year, what the key does and does not do, and whether you have a spare that works. That usually narrows it down before we arrive. We cut, code and program car keys at your location in Kempton Park. See our car keys and programming service.
Next step
Need help in Kempton Park? See our car keys & programming service or send your vehicle details to arrange a mobile assessment.