Fuel Sender Circuit Short To Ground
Your fuel gauge sender has a short circuit touching ground, like a broken wire letting electrical current escape instead of reaching the gauge. The ECU detects abnormally low resistance where it should see varying levels as the fuel tank empties.
The ECU sends a reference voltage to the fuel sender and measures the returning resistance. As the float moves in the tank, resistance should vary from ~240Ω (full) to ~33Ω (empty). A short to ground causes abnormally low resistance outside normal operating parameters, triggering the fault code.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sender Resistance | 33–240 ohms depending on fuel level | 0–5 ohms (short to ground) |
| Sender Voltage Signal | 0.5–4.5 volts | Below 0.2 volts |
Code B1204 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, B1204 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.