* Faulty injector: The injector itself might be internally shorted or stuck open. This means the solenoid inside remains energized, even when the engine control unit (ECU) isn't signaling it to inject fuel. This is the most likely cause.
* Wiring harness problem: A short circuit in the wiring harness leading to the injector can provide constant power. This could be a broken wire touching ground or another positive voltage source.
* ECU malfunction: A faulty ECU could be sending a continuous signal to the injector, though this is less common than a wiring or injector problem. The ECU typically controls the precise timing and duration of the injector pulses.
* Power supply issue: A problem with the vehicle's main power system (e.g., a short in the positive battery cable) could cause constant power to the injector circuit. This is less specific to the injector itself, but would have broader consequences.
* Relay failure: The fuel injector relay might be stuck closed, constantly providing power to the circuit.
In short, constant power to a fuel injector is a serious problem that will result in excessive fuel consumption, a rich fuel mixture (potentially leading to engine damage), and likely a misfire or poor engine performance. You need to diagnose and fix the underlying cause, not just address the symptom. A mechanic can diagnose the issue with diagnostic equipment and determine whether the fault is with the injector, the wiring, or the ECU.
