Fuel Temperature Sensor #1 Circuit Open
The fuel temperature sensor isn't sending a signal to the engine computer, like a broken thermometer that can't tell you how hot the fuel is. The ECU can't adjust fuel injection timing and pressure properly without this data.
The ECU monitors voltage from the fuel temperature sensor to determine fuel density and optimize injection timing and pressure. An open circuit means zero or invalid voltage signal is received for an extended duration. The ECU expects a continuous analog signal within a specific range; anything outside triggers the fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor Voltage | 0.5–4.5V (varies by temperature) | Below 0.1V or above 5V for >2 seconds |
| Signal Continuity | Continuous valid signal | Open circuit / no signal detected |
Code B1223 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B1223 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.