Cylinder 1 Injector Circuit High
The fuel injector for cylinder 1 has an electrical problem where the voltage is too high, preventing the injector from opening properly. Think of it like a water valve stuck closed because the electrical signal trying to open it is too strong.
The ECM monitors the voltage and current flowing through the fuel injector circuit during each firing event. It detects when the injector circuit voltage remains abnormally high during the opening command, indicating a short to voltage or open circuit in the injector wiring or driver.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Injector Circuit Voltage | 12V pulse during activation, 0V at rest | Voltage remains above 14.5V or fails to drop below threshold during injection cycle |
| Injector Current Draw | 1-4 amps during activation | No current draw or excessive resistance detected |
Code P0263 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, P0263 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.