P0037: HO2S Heater Control Circuit Low (Bank 1 Sensor 2)

P0037 means the engine computer measured too little current or too low a voltage in the heater circuit of the downstream oxygen sensor on bank 1, the one after the catalytic converter. That is what a burned-out heater, a blown fuse or a broken supply wire produces. The sensor only checks the converter, so the car usually drives exactly as before. A new downstream sensor typically costs about 110 to 270 EUR fitted.

P0037 is a emissions-related diagnostic trouble code classified as low severity. When your vehicle's ECU detects this condition, it stores P0037 and illuminates the check engine light.

If your vehicle has triggered P0037, you may notice one or more of these symptoms:

• Check engine light on, usually with no change in how the car drives
• No noticeable effect on power or fuel economy in most cars
• Catalyst monitor slow to complete, or incomplete after the code is cleared
• Oxygen sensor heater readiness monitor incomplete after the code is cleared
• Possible rejection at an emissions inspection while the warning light is on

Here are the most common causes of P0037:

Generally yes, for short-term driving. Safe to drive. The sensor after the catalytic converter only checks how well the converter works; it does not set the fuel mixture, so the engine runs as before. Without its heater the sensor takes longer to warm up and the converter check may not complete. Fix it promptly: the warning light hides any new fault and can get the car rejected at an emissions inspection.

Follow these steps to pinpoint the root cause of P0037:

1. Read all stored codes and freeze frame. P0037 together with P0031, P0057 or other heater codes points to a shared fuse, relay or supply wire rather than several failed sensors
2. Check the oxygen sensor heater fuse named in the owner's manual or on the fuse box lid. Replace it if blown, and if it blows again look for a short in the heater or its wiring
3. Raise the car safely, unplug the Bank 1 Sensor 2 connector and measure the resistance across the two heater pins. Many downstream sensors read between about 3 and 15 ohms at room temperature; check your car's specification. An open circuit means the heater has burned out
4. With the key on, check for battery voltage on the heater supply pin on the harness side of the connector. No voltage points to the fuse, relay or supply wire
5. Inspect the connector and the wiring along the exhaust and underbody for corrosion, pushed-back pins, melted insulation or chafing, and repair as needed
6. After the repair, clear the code and drive a mix of town and steady faster driving. With a generic OBD2 reader, check that the oxygen sensor heater and catalyst readiness monitors complete before an inspection

Repair costs for P0037 vary depending on the root cause and your vehicle. Here are typical estimates:

P0037 behaves differently depending on your vehicle. Select your car below for model-specific causes and known issues:

These codes are often seen alongside P0037 or indicate related issues: