Fuel & air metering · Powertrain · generic (SAE-defined)
P0037: HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
P0037 means the engine computer sees lower-than-expected voltage or current in the heater circuit of the Bank 1 downstream oxygen sensor, the one after the catalytic converter.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0037 sets
The powertrain control module (PCM) controls the heater in the Bank 1 Sensor 2 heated oxygen sensor (HO2S) and monitors the circuit. A "low" code generally means the PCM sees the circuit voltage or current lower than expected, which can point to an open heater, an open wire or a short to ground, depending on how the manufacturer designed the circuit.
Common causes of P0037
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Open heater element in the Bank 1 Sensor 2 oxygen sensor
- Wire shorted to ground or broken under the vehicle
- Corroded or water-damaged connector
- Blown fuse feeding the heater
- PCM driver fault (rare)
P0037 symptoms
- Check engine light on
- Typically no drivability symptoms
- Readiness monitors incomplete
- Possible failed emissions inspection
How P0037 is diagnosed
- Scan for codes; note any P0036 or P0038
- Inspect wiring and connector for damage, corrosion or contact with the exhaust
- Check the heater fuse and supply voltage
- Measure heater resistance at the sensor
- Test the control wire for shorts to ground
- Repair and confirm with a completed drive cycle
Typical fixes for P0037
- Replace the Bank 1 Sensor 2 oxygen sensor
- Repair grounded or broken wiring
- Clean or replace the connector
- Replace the fuse after correcting the short
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0037 FAQ
What does code P0037 mean?
P0037 means the engine computer sees lower-than-expected voltage or current in the heater circuit of the Bank 1 downstream oxygen sensor, the one after the catalytic converter. The standard definition is "HO2S Heater Control Circuit Low (Bank 1 Sensor 2)."
Can I drive with a P0037 code?
Yes, you can normally keep driving because engine performance is rarely affected. Repair it reasonably soon so the emissions monitors can complete.
What is the difference between P0037 and P0038?
P0037 indicates the heater circuit reads low, often from an open or short to ground, while P0038 indicates it reads high, often from a short to voltage.
Can a universal oxygen sensor fix P0037?
A universal sensor can work if spliced correctly, but a direct-fit sensor with the factory connector avoids wiring errors that can cause the code to return.
Keep researching
Engine guides by brand (known issues, specs)
More fuel & air metering codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.