Cylinder 8 Injector Circuit High
The engine's computer detected that cylinder 8's fuel injector isn't responding correctly—the electrical signal is staying too high instead of cycling on and off normally. Think of it like a light switch stuck in the partial-on position instead of flicking between fully off and fully on.
The ECM monitors injector voltage and pulse patterns through the injector driver circuit. It expects the voltage to drop to near 0V when the injector fires and return to battery voltage when off. A continuously high voltage signal indicates a wiring short, stuck relay, or internal injector failure.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Injector Circuit Voltage | 0-12V cycling at fuel pressure demand | Voltage remains above 10V continuously |
| Injector Pull-Down Time | 1.5-3.5ms pulse width | No voltage drop detected over 100ms period |
Code P0284 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0284 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.