Heated Oxygen Sensor (HO2S) Heater Circuit Low Voltage Bank 1 Sensor 2
The oxygen sensor heater on Bank 1, Sensor 2 (downstream of catalytic converter) isn't getting enough electrical power to warm up properly. Think of it like a car's seat warmer not heating because the electrical circuit is weak or broken.
The ECM monitors the voltage supply to the HO2S heater circuit during cold start and idle conditions. The heater element must reach operating temperature quickly so the sensor can generate an accurate voltage signal for fuel trim calculations. If the ECM detects voltage below threshold for too long, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| HO2S Heater Supply Voltage | 12-14V during operation | Below 10.5V or open circuit detected |
| Heater Circuit Resistance | 4-14 ohms cold | Open or shorted circuit condition |
Code P0037 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, P0037 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.