* Ignition Switch: This is the most likely culprit. The ignition switch is a complex mechanism that controls power to various systems. If it fails internally, it can prevent the key from turning, locking the steering wheel. A faulty ignition switch often exhibits intermittent problems before completely failing.
* Ignition Cylinder: This is the part where the key goes. While less common than a failing ignition switch, a problem with the cylinder itself (wear, damage, etc.) could prevent the key from turning properly and locking the steering.
* Steering Column: Less likely, but possible, damage to the steering column's locking mechanism could prevent the key from turning and unlocking the steering wheel. This would usually be due to a collision or significant impact.
* Binding in the Steering Wheel: Sometimes, if the steering wheel is turned slightly at an awkward angle while the car is off, the locking mechanism can engage tightly. Try gently jiggling the wheel while turning the key. (This is less likely if the car was running normally moments before.)
How to try to diagnose:
1. Gently jiggle the steering wheel: See if you can freely move it. If it's very stiff or stuck, the problem might be mechanical in the steering column or lock mechanism itself.
2. Try the key in different positions: Sometimes a slightly misaligned key or a dirty cylinder can cause problems. Try very slightly turning the key and jiggling it in various positions. Clean the key (if needed) and the keyhole with compressed air.
3. Listen for any unusual noises: When you try to turn the key, listen for any clicking, grinding, or other sounds that might indicate a problem with the ignition switch or cylinder.
Important Note: If you can't resolve this easily, it's best to call a locksmith or tow the car to a qualified mechanic. Forcibly trying to unlock the steering wheel or ignition could cause further damage. Improperly handling the situation can lead to damage that results in an expensive repair.
