Immobilizer light flashing and car won't start

Symptoms

• Small key-shaped or padlock icon flashes on the dash
• Engine cranks but doesn't fire, or won't crank at all
• May start fine with a different key
• Sometimes resolves after a wait or several attempts

Likely causes

• CommonKey transponder chip not being read properlyWear, damage, or interference can prevent the chip's signal from being confirmed.
• CommonLow key fob or transponder batteryWeak battery power reduces the chip's transmission strength.
• PossibleToo many keys or metal objects on the keyringExtra items can interfere with the antenna ring reading the correct key.
• PossibleImmobilizer module or antenna ring faultThe ring around the ignition that reads the chip can fail or corrode.
• Less commonAftermarket alarm or remote start conflicting with the factory immobilizerPoorly installed aftermarket systems can interfere with the factory security signal.

What to do

1. Remove all other keys and fobs from the ring and try starting with just the one key.
2. Try your spare key, since a worn chip in the primary key is a common and simple explanation.
3. Replace the key or fob battery if it hasn't been changed recently.
4. Turn the key to 'on' and leave it for 5–10 minutes, then try again, since some systems have a timeout/reset behavior.
5. Check your owner's manual for any model-specific reset steps for the immobilizer light.
6. If you've had an aftermarket alarm or remote start installed, have the installer check for interference with the factory system.
7. Have a dealer or qualified locksmith test the key chip and the antenna ring around the ignition if basic steps fail.
8. Avoid using uncut or improperly programmed aftermarket keys long-term, since they can cause recurring immobilizer faults.

Tools and parts

• Spare key if available

When to call a pro

If a spare key and a fresh battery don't clear the flashing immobilizer light, a dealer or automotive locksmith with the right equipment can diagnose the key and antenna ring.

Safety