HO2S Heater Control Circuit High (Bank 1, Sensor 3)
The oxygen sensor heater for Bank 1, Sensor 3 (located after the catalytic converter) isn't warming up properly, like a heating element that's stuck on high. The ECU detected excessive voltage in the heater circuit, indicating an electrical problem rather than a sensor malfunction.
The ECU monitors the voltage supplied to the O2 sensor heater element, which pre-warms the sensor for faster response. When voltage exceeds the safe operating threshold (typically above 14.5V or sensor resistance drops too low), the ECU logs a fault. The heater should cycle on and off, not run continuously at high voltage.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Heater Circuit Voltage | 0-14V with normal cycling | >14.5V sustained or open/short condition detected |
| Heater Resistance | 4-14 ohms at idle | <2 ohms (short) or >25 ohms (open) |
Code P0044 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, P0044 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.