Simple Checks (but potentially dangerous - use caution):
* Battery: This is the most common culprit. Check the battery terminals for corrosion (white or green buildup). Clean them with a wire brush and baking soda solution if necessary. If the terminals are clean, try jumping the car with another vehicle's battery. If it still doesn't work, the battery itself is likely dead or failing.
* Battery Cables: Inspect the cables connecting the battery to the car. Are they loose, damaged, or corroded? Tighten loose connections (but don't overtighten).
* Ignition Switch: A faulty ignition switch can prevent power from reaching the rest of the system. This is harder to diagnose yourself.
Things that likely require a mechanic:
* Alternator: While the alternator charges the battery while the engine is running, a faulty alternator can drain the battery when the car isn't running. A dead battery after sitting overnight might point to this.
* Starter Motor: A completely dead starter won't crank the engine at all. This usually involves a lack of cranking noise. While it *might* explain a lack of power, other symptoms usually accompany this.
* Wiring Issues: A short circuit or a broken wire in the main power supply can cut off all power. This is very difficult to diagnose without specialized tools.
* Immobilizer System: If your car has an immobilizer system, the key might not be recognized. Try a spare key if you have one.
* Fuse Box: Check your car's fuse box (usually under the hood or dashboard) for blown fuses. Replace any that are blown, but ensure you replace them with the correct amperage.
* Ignition Coil (less likely): This is less likely to cause *complete* power loss, but worth considering if you've ruled out the above.
Important Safety Considerations:
* Don't attempt any major repairs yourself unless you are experienced. Working on a car's electrical system can be dangerous.
* If you smell burning rubber or smoke, turn off the ignition and do not attempt to start the car.
* If you are on the side of the road, call for roadside assistance. This is safer and more efficient than trying to diagnose the problem yourself in a potentially hazardous location.
If none of the simple checks work, you *absolutely* need to have the car towed to a mechanic for proper diagnosis and repair. Describing the symptoms accurately to the tow truck driver and the mechanic will help them determine the most likely cause.
