* Ignition switch failure: The ignition switch might be faulty and not properly breaking the circuit when turned off. This is a common culprit.
* Wiring short: A short circuit in the wiring harness could be providing power to the starter or fuel system, bypassing the ignition switch. This could be a frayed wire, a damaged connector, or a wire touching a ground point where it shouldn't.
* Stuck relay: Relays control various electrical components. A relay related to the ignition system or fuel pump might be stuck closed, constantly supplying power.
* Faulty starter: In rare cases, a faulty starter could be engaging even without the ignition key. However, this is less likely, as it typically manifests as cranking without starting.
* Aftermarket accessories: If any aftermarket accessories have been installed, their wiring could be interfering with the ignition system's circuitry.
It's crucial to address this immediately. Running the engine with the key off is extremely dangerous:
* Battery drain: The battery will quickly discharge, leaving you stranded.
* Fire hazard: A short circuit can lead to overheating and potentially a fire.
* Accidental injury: Someone could accidentally start the car when it's not intended.
Do not attempt to drive the car. Have it towed to a qualified mechanic or auto electrician to diagnose and repair the problem. They have the tools and expertise to safely locate and fix the short circuit or faulty component.
