Fuel Temperature Sensor B Circuit High Input
Your fuel temperature sensor is sending a signal that's too high, like a thermometer stuck at the hottest reading even when conditions are normal. The engine computer thinks the fuel is much hotter than it actually is, which can affect fuel injection timing and efficiency.
The ECU monitors resistance from the fuel temperature sensor (typically located in the fuel rail or tank) to calculate fuel temperature. When voltage input exceeds the maximum threshold (usually around 4.5V, indicating extremely cold/impossible conditions), the ECU registers a high input fault. This voltage-to-temperature conversion helps the engine adjust fuel injection parameters for optimal combustion.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Fuel Temperature Sensor Voltage | 0.5V to 4.5V (−40°C to +125°C) | >4.5V (circuit shorted high or sensor failed) |
| Sensor Resistance | 100–10,000 Ohms (varies by design) | Open circuit or extremely low resistance |
Code P0189 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, P0189 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.