P0286 indicates the engine computer (PCM) has detected an abnormally high voltage condition, excessive resistance, or a short-to-voltage in the electrical circuit controlling the fuel injector for cylinder 9. This typically means the injector coil, its wiring, or a connector is not allowing the circuit to operate within the expected range.
An open or high-resistance injector coil, or an internal short, is the most common cause. The injector may fail electrically even if it sounds normal during a basic click test.
The control or ground wire for cylinder 9 may be chafed, pinched, or shorted to another voltage source, producing the high-voltage signal the PCM reports.
Corroded, spread, backed-out, or damaged pins at the injector connector can create high resistance or an intermittent open circuit.
If the injector control wire touches a reference voltage, battery voltage, or another powered circuit, the PCM will see a circuit-high condition.
A failed or stuck-high driver inside the PCM is possible but uncommon; it should only be considered after the injector, connector, and wiring have been ruled out.
Most real-world cases are caused by a failing fuel injector, followed by connector or wiring problems. A PCM failure is much less common.
It is not advisable to drive for long; a misfiring cylinder can damage the catalytic converter and cause poor performance or unsafe drivability.
Usually not. PCM replacement is commonly suggested for injector circuit codes but is rarely the actual cause. Verify the injector, connector, and wiring thoroughly before considering the PCM.
Yes, if the cause is corrosion or a poor connection at the injector plug. However, if the injector coil itself is open or the wire is shorted, cleaning alone will not resolve it.