Why Can the Key Unlock but Not Start the Car?

[DelaneyLee]

Key can unlock but not start the car because it needs decoding and installing a chip to start. Here are the specific reasons and solutions: 1. The key does not have a chip: Nowadays, cars use electronic injection keys with built-in chips. If only the key is duplicated without the chip, it cannot function properly. Solution: Drive to a car locksmith shop to match the chip and decode it. 2. The key is not registered: The car has an engine immobilizer function, and the key contains a chip. Solution: The new key must have a chip and needs to be decoded and registered using a computer. Only after the key is properly configured can the car be started. 3. The car does not recognize the key: The car's anti-theft system may not recognize a key that was not originally provided by a 4S store and has not been matched with the vehicle. This means the duplicated key's teeth may match the original, but the car's anti-theft system prevents starting as it considers it a theft attempt. Solution: Match the key with the vehicle.

[StClaire]

As a veteran driver with twenty years of experience, I've encountered this situation several times. If the key can unlock the door, it means the remote and lock cylinder are fine. The most common reason for the engine not starting is a dead battery, especially in older cars. Try honking the horn or turning on the headlights to see if they work. If the lights are dim or the dashboard is flickering, it's almost certainly a battery issue. There's also a small chance it could be a key chip sensor malfunction—though rare, the repair shop handled a few cases like this last year. If all else fails, calling for roadside assistance to jump-start the car is the easiest solution. Don't force the key and risk burning out the starter.

[OAdriel]

It depends on whether it's a new or old car. For vehicles within three years, it's likely due to insufficient battery power. In hot weather, the dashcam continues to drain the battery after parking, making it hard to start the next day. Also, check if the steering wheel is locked - gently wiggle it while turning the key. For older cars, consider aging components like ignition coils or crankshaft position sensors. Last month, my neighbor's car broke down for this reason. Avoid turning the key continuously for more than five seconds, and it's best to call a professional mechanic for inspection.

[BennettLynn]

If the key can unlock but fails to start the car, first check three things: battery status (see if the dashboard flickers after power-on), gear position (automatic transmissions must be in P), and whether the brake pedal is fully depressed. Once I was in a hurry to leave work and turned the key without pressing the brake—the car didn’t respond at all. If the dashboard doesn’t light up at all, it might be a main relay failure; if the dashboard lights but the engine makes no sound, there’s a high chance the starter motor is broken. These parts aren’t expensive to replace at a repair shop.