Key Turns but the Car Won't Start? Check These First
When a key turns but the car will not start, the immobiliser often is not recognising the key. What the light means, what to try, and when it is the key.
A key that turns but won't start the car usually isn't being recognised by the immobiliser. The cause is often a weak battery or a failed chip.
What the immobiliser is checking
Most cars built in the last twenty years have a small chip in the key. When you turn the key, the car reads that chip and only lets the engine run if the code is right. A wrong or unreadable code leaves the key turning the ignition but the engine not starting.
The manufacturer's manual describes the same behaviour. Hyundai's says that if the immobiliser indicator starts to blink, the system does not recognise the coding of the key. Mazda's says the engine may not start, and the security light may flash, if the key sits where the system struggles to read it.
What to check first
- Look at the security light. A short flash when you turn the key on is normal. A light that keeps blinking, or stays on, points to the immobiliser.
- Take other keys and metal off the key. Hyundai's manual warns that metal objects near the key can interfere with the signal. Mazda's names another registered key, or keys for other vehicles, near the ignition or start button.
- Turn the ignition off, then try again. Both manuals suggest switching off and restarting once before anything else.
- Try your spare key. If the spare starts the car, the original key is the problem, and the car is fine.
- Check the car battery. A weak 12V battery can cause a no-start that looks like a key fault.
If it still won't start after a few tries, stop. Both manuals say to contact the dealer or a specialist if the system keeps rejecting the key.
When it is the key
A chip can fail, or stop being read, for a few ordinary reasons:
- the key has been dropped, crushed or gone through the wash
- the shell has been swapped and the chip was left behind
- the key was cut at a hardware store and never programmed to the car
- the chip has simply worn out
If the spare works and the main key doesn't, that points to the key. A damaged key may be repairable, which is covered in can a broken car key be repaired. One that has lost its chip needs a new key programmed to the car, which is transponder key programming.
When it is not the key
A flat car battery, a starter fault and a fuel problem can all leave the car not starting while the key is fine. We can tell you quickly whether it looks like a key fault, and we won't claim to fix a problem that isn't one.
Keyless cars are different. If the car says it can't find a smart key, see smart key not detected. If the key won't turn at all, or the steering wheel is locked, see the VW, Audi and Skoda ignition guide or steering lock jammed.
Getting it sorted in Hamilton
We come to the car anywhere in Hamilton, test the key, and tell you what is wrong before any work starts. If the key needs programming or replacing, the price is confirmed first. Send the make, model, year and what the light does and we will tell you what is involved.
Where the fault is the car's immobiliser itself, our immobiliser programming service covers that.
Common questions
Why does my car key turn but the car won't start?
Usually because the immobiliser isn't recognising the chip in the key. Other causes are a weak car battery, interference near the key, or a fault in the car. Trying your spare key quickly shows whether the key is the problem.
What does a flashing security light mean?
On many cars it means the immobiliser doesn't recognise the key. Hyundai's manual says a blinking indicator means the system does not recognise the coding of the key. The exact meaning varies by car, so check your own manual.
Can a flat key battery stop the car starting?
On a keyless car, yes, it can. On a traditional chip key the chip is usually read without the remote's battery, so a flat remote is a less likely cause. If the buttons stopped working too, replace the battery as a first step.
Can you program a new key at my home in Hamilton?
Yes. We come to the car and program the key there. A transponder key is usually $120–$180, depending on the make, model and year, and the price is confirmed before any work starts.