Short answer
The key or immobilizer light means the car has not recognized the key, or the key fob battery is getting low. If the car started and runs normally, you can drive, but replace the fob battery soon. If it will not start, try the spare key and the backup position for a weak fob described in your owner's manual.
- Also shown as:
- Immobilizer light · Security light · “Key not detected” message · Key fob battery low
- What it looks like:
- A key outline, sometimes inside a car shape or with a padlock; a flashing security light when parked is usually normal.
Is it safe to keep driving?
If the car started, yes. If it will not start, the car has not recognised the key.
What causes the key / immobilizer light?
Most common first. Symbols and meanings vary by manufacturer; your owner's manual has the definitive meaning for your model.
- Key fob battery low or flat. The most common cause. The car may still start using a backup reading position, but the remote and keyless entry fade first.
- Key not in range or blocked. Phones, other keys or metal cases near the fob can block its signal, and keyless cars warn when the key leaves the car.
- Damaged transponder chip. A dropped or water-damaged key can lose the chip the immobilizer reads, so the engine will not start with that key.
- Immobilizer antenna or module fault. The ring around the ignition or the antenna in the cabin can fail, so no key is recognized.
What should you do right now?
- Try the spare key.
- Hold the fob against the start button or the marked spot on the steering column — most cars have an emergency reading position.
- Replace the fob battery; the type is usually printed on the old one.
What does the fix usually involve?
A new fob battery fixes most cases. A damaged key is replaced and programmed to the car by a dealer or automotive locksmith; an antenna or module fault is diagnosed from the codes.
How much does it cost to fix?
$5 – $400
A fob battery at the low end; a new programmed key at the high end.
A typical range, not a quote. Actual cost depends on the car, the shop and the fault.
Common questions
Why is my security light flashing when the car is off?
On many cars a slowly flashing security light while parked simply shows the immobilizer is armed. It is a problem only if it stays on or flashes fast when you try to start.
Can I start my car with a dead key fob?
Usually yes. Most keyless cars have a backup: hold the fob against the start button or put it in a marked slot, and many fobs hide a mechanical key for the door. The owner's manual shows where.
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