Nissan Altima wont start why?

1. Dead or Weak Battery: A common issue is a drained or faulty battery. Check the battery terminals for corrosion and ensure they are properly connected.
2. Faulty Starter: The starter motor is responsible for turning the engine over. A malfunctioning starter can prevent the engine from cranking.
3. Fuel-Related Problems: Check if the vehicle has sufficient fuel. A clogged fuel filter or a faulty fuel pump could also be the culprit.
4. Ignition System Issues: Check components like spark plugs, ignition coils, and ignition wires for any issues that could prevent a proper spark from reaching the engine.
5. Malfunctioning Sensors: Certain sensors provide vital information for the engine to operate. Faulty sensors can disrupt the engine's ability to start.
6. Immobilizer Problems: Some Nissan models have an immobilizer system to prevent theft. Issues with the key, transponder, or immobilizer module could immobilize the vehicle.
7. Electrical Issues: Faulty wiring or electrical connections can cause problems with the starter, fuel pump, or other systems necessary for starting.

Note: Without further diagnostic information, it's challenging to pinpoint the exact reason why your Nissan Altima won't start. It's always best to consult a professional mechanic or visit an authorized Nissan service center for a proper diagnosis and repair.