Fuel & air metering · Powertrain · generic (SAE-defined)
P0038: HO2S Heater Control Circuit High (Bank 1 Sensor 2)
P0038 means the engine computer sees higher-than-expected voltage or current in the heater circuit of the downstream Bank 1 oxygen sensor, after the catalytic converter.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0038 sets
The powertrain control module (PCM) switches the heater inside the Bank 1 Sensor 2 heated oxygen sensor (HO2S) and checks the circuit state. A "high" code means the circuit reads higher than the PCM expects, such as a control wire shorted to battery voltage or a heater drawing excessive current. The exact logic differs between manufacturers.
Common causes of P0038
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Shorted heater inside the Bank 1 Sensor 2 oxygen sensor
- Heater control wire shorted to voltage
- Damaged harness rubbing on the exhaust or body
- Connector damage or wrong-fit aftermarket sensor
- PCM heater driver fault (rare)
P0038 symptoms
- Check engine light on
- Usually no noticeable drivability change
- Incomplete catalyst or oxygen sensor monitors
- May fail emissions testing
How P0038 is diagnosed
- Scan for codes and freeze frame
- Inspect wiring and connector along the exhaust
- Measure heater resistance; very low resistance suggests a shorted heater
- Check the control wire for a short to voltage
- Verify the correct part number if a sensor was recently replaced
- Repair and verify the code does not return
Typical fixes for P0038
- Replace the Bank 1 Sensor 2 oxygen sensor
- Repair wiring shorted to voltage
- Replace a damaged connector
- Install the correct direct-fit sensor
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
P0038 FAQ
What does code P0038 mean?
P0038 means the engine computer sees higher-than-expected voltage or current in the heater circuit of the downstream Bank 1 oxygen sensor, after the catalytic converter. The standard definition is "HO2S Heater Control Circuit High (Bank 1 Sensor 2)."
Can I drive with a P0038 code?
Yes, it is usually safe to drive because the engine typically runs normally. Get it fixed in the near term so the vehicle can pass an emissions inspection.
Why did P0038 appear right after replacing the oxygen sensor?
An incorrect sensor, a damaged connector or a wire pinched during installation can all set this code. Recheck the part fitment and wiring routing.
Does P0038 mean the catalytic converter is bad?
No. It is an electrical heater circuit fault on the downstream sensor, not a converter efficiency problem.
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.