What are the reasons why a car cannot be turned off?

[McGraham]

The reason why a car cannot be turned off is likely due to damage inside the ignition switch. The ignition switch has ACC, ON, and START positions. Turning to ACC powers the car's electrical equipment; ON powers the ABS (Anti-lock Braking System), AIRBAG (airbag), fuel pump, and ECU power supply, among others; while START is for ignition. Solutions for not being able to turn off the car are as follows: 1. Directly disconnect the fuel line switch. This mechanical fuel line switch varies in location depending on the car model—some are under the seat, while others are on the lower left side of the steering wheel. 2. For electronically controlled diesel engines, similar to car keys, they only power on when in the ON position, with the ECU controlling the fuel injectors to spray fuel. Therefore, turning off the key for such diesel engines stops the fuel injectors, effectively cutting off the fuel supply.

[Matthew]

I've seen many cases where a car won't shut off. The most common issue is a faulty ignition switch—worn or stuck internal contacts prevent the circuit from breaking, so the engine keeps running even after turning the key. Relays often fail too; if stuck in the "on" position, the power supply won’t cut off. Electrical shorts are another possibility, such as damaged wiring allowing continuous current flow. Anti-theft system malfunctions can cause the ECU to ignore shutdown signals, or the engine control module itself may be defective. Start troubleshooting with simple steps: check the fuse box for blown fuses and try turning the key repeatedly to see if it resolves. If not, seek professional repair immediately—prolonged operation risks engine damage or fire hazards, especially if ignored while driving.

[LaCarson]

I always pay attention to these issues when driving. When my car had difficulty turning off, I personally experienced a situation with aging relays—the engine kept roaring even after removing the key, which was quite unsettling. There can be many reasons, such as loose switch buttons or short circuits caused by water in the wiring, especially in humid weather. For new cars, sometimes a computer bug can be resolved with a restart, but for older cars, it's necessary to check if the contacts are oxidized. It's advisable to regularly maintain switches and circuits to prevent long-term issues. If this happens, pull over, engage the handbrake, and try turning off all power sources. Don’t delay repairs to avoid battery drain or the risk of spontaneous combustion—safety should always come first.

[RicardoLee]

A car that won't shut off is quite dangerous. I've seen cases where damaged ignition coils or poor wire connections caused the engine to keep running even after turning off the key. Continuing to drive could lead to engine overheating, significantly increased fuel consumption, and even potential fire hazards. From a safety perspective, immediately pull over, turn off the lights, lock the car and restart the anti-theft system to see if it resolves. If not, disconnect and reconnect the battery. For prevention, regularly inspect ignition components and wiring connections. Timely repairs are crucial - don't skimp on small expenses when safety is at stake.

[LeArcher]

From a holistic system perspective, the difficulty in stalling a small car may stem from a faulty ignition switch, relay malfunction, wiring short circuit, anti-theft module conflict, or ECU control error. When addressing the issue, proceed step by step: first, check if the fuses are intact; inspect whether the key turns smoothly; verify if the relay makes normal sounds; examine the grounding wire. DIY repairs carry risks, but understanding these aspects can facilitate better communication with technicians, saving trouble. Early detection and repair of issues can prevent the escalation of faults.