P0038: HO2S Heater Control Circuit High (Bank 1, Sensor 2)
Key takeaways
- P0038 means the engine computer saw a voltage that was too high in the heater circuit of the downstream oxygen sensor on bank 1, the one behind the catalytic converter.
- The heater only helps the sensor warm up fast, and the rear sensor mainly checks the converter, so the car drives normally; expect a failed OBD emissions check.
- Depending on how the computer drives the heater, 'high' can mean a short to power or an open heater, so check wiring and the connector before a $150–$400 sensor.
- Several bulletins fix P0038 with software, including engine computer updates for the 2024 Jeep Wrangler and Gladiator, the 2024 Ram ProMaster and the 2021 Chrysler Pacifica.
What P0038 means
The heater in the oxygen sensor behind your catalytic converter on bank 1 isn’t behaving the way the engine computer expects. The scanner name is HO2S Heater Control Circuit High (Bank 1, Sensor 2). An oxygen sensor only reads accurately when it’s hot, so it has a small electric heater. The computer switches that heater on and off and watches the voltage on its control wire. When the voltage stays higher than it should for the heater’s commanded state, it sets P0038.
On many cars the computer switches the ground side of the heater, so a heater that has burned open can read “high” as well as a wire shorted to power; which one applies depends on the design. Sensor 2 is the downstream sensor, after the converter. Bank 1 is the side of the engine with cylinder 1; on a four-cylinder it’s the only bank.
Is it safe to drive?
Yes. The rear sensor mainly tells the computer whether the converter is working, and without its heater it simply takes longer to start reporting. The car drives the same; it will fail an OBD-based emissions inspection while the light is on, and the converter test may not run.
What changes the answer: a flashing check engine light, rough running, or several unrelated sensor codes at once. Those point to a bigger problem or a shared fuse or wiring fault worth finding before it strands you.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Heater element burned out inside the sensor | Heater resistance open or far out of spec at the sensor side of the connector | $150–$400 |
| Corroded, wet or melted connector | Green or burned pins; water in the plug; code comes and goes | $100–$250 |
| Chafed or shorted wiring under the car | Wire rubbed through on a bracket or melted on the exhaust; heater control wire shows voltage when it shouldn’t | $100–$250 |
| Engine computer software (some makes) | A bulletin for your exact model and year names P0038 | $100–$200, often $0 under warranty |
| Blown fuse for the O2 heater circuit | No power at the heater feed with the key on; other heater codes too | $0–$20 for the fuse, plus diagnosis |
A failed heater is the most common final answer, and it’s built into the sensor, so you replace the whole sensor. But wiring, the connector and software are worth ruling out first.
What to check first
- Look for a bulletin. P0038 has more software fixes than most sensor codes, and a reflash costs less than a sensor.
- Inspect the connector and wiring under the car with the engine cold. Unplug it, check for water, corrosion or melted plastic, and make sure the harness isn’t touching the exhaust.
- Measure heater resistance at the sensor side of the connector and compare with the service manual. Open or far off means a new sensor.
- Check power, ground and the control wire at the harness side with the key on. A control wire that shows battery voltage with the sensor unplugged points to a short in the harness.
- Check the fuse if other heater codes are set too, and find the short before replacing it.
- Clear the code and drive after a repair; the heater monitor reruns on the next cold start.
The bulletins lean heavily on software. Stellantis has engine computer updates naming P0038 for the 2024 Jeep Wrangler and Gladiator, the 2024 Ram ProMaster and the 2021 Chrysler Pacifica. Jaguar and Land Rover cover heated oxygen sensor codes on the 2013–2015 XF, 2015–2016 F-Type and 2016 Range Rover, and GM lists P0038 among oxygen sensor codes on 2013–2015 Acadia, Enclave and Traverse.
What it costs
The cheap outcome is a fuse or a cleaned and resealed connector, under $20 in parts, or a software update, often free under warranty. The common outcome is a new downstream oxygen sensor, $150–$400 installed. The other outcome is a wiring repair at $100–$250, sometimes plus a sensor. A $100–$180 diagnosis that checks the circuit and looks up bulletins keeps you from buying a sensor when the fix is a connector or a reflash.
Related codes
P0038 often appears with P0037 (same heater circuit reading low) or P0141 (heater performance for the same sensor). If the upstream heater codes P0030 or P0031 are also set, suspect a shared fuse, relay or power feed before replacing several sensors. A heater fault can also lead to P0138 readings on the same sensor. More on the light itself: can I drive with the check engine light on.
What owners report to NHTSA
2 complaints filed with NHTSA mention P0038, 1 of them since 2015, across 2 different models. The component owners most often filed it under: electrical system.
Manufacturer service bulletins that name P0038
40 technical service bulletins and manufacturer communications filed with NHTSA mention P0038, from 12 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- JEEP WRANGLER (2024), bulletin 11005721: "Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): **P…
- JEEP GLADIATOR (2024), bulletin 11006253: "Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): P00…
- RAM PROMASTER (2024), bulletin 11008749: "Flash: Powertrain Control Module (PCM) Updates Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Code (DTC): P0032…
- CHRYSLER PACIFICA (2021), bulletin 10198455: Flash: Powertrain Control Module (PCM) Updates This bulletin involves reprogramming the PCM with the latest available software. Customers may experience a Malfunction Indicator Lamp (MIL) illumination. Upon further inves…
- VICTORY MAGNUM (2016, 2017), bulletin 10178937: Victory has determined that some 2016-2017 106 ci motorcycles may set false-positive P0032 and P0038 trouble codes for the Oxygen Sensor heater circuit. Victory has developed an updated ECM calibration to improve the O2 …
- VICTORY HARDBALL (2016, 2017), bulletin 10178938: Victory has determined that some 2016-2017 106 ci motorcycles may set false-positive P0032 and P0038 trouble codes for the Oxygen Sensor heater circuit. Victory has developed an updated ECM calibration to improve the O2 …
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Can I drive with P0038?
Yes. The heater only speeds up how fast the rear sensor starts working, and the rear sensor mostly checks the catalytic converter. The engine runs normally; the light will fail an OBD-based emissions inspection.
Is P0038 the oxygen sensor itself?
Often, but not always. The heater is built into the sensor, and a failed heater means a new sensor. But a shorted or corroded connector, chafed wiring, or engine software can set the same code, so check those first.
What's the difference between P0037 and P0038?
Both are the heater circuit of the same rear sensor. P0037 means the circuit reads low, P0038 means it reads high. The checks are the same: fuse, connector, wiring, heater resistance, then the sensor.
Where is bank 1 sensor 2?
It's the oxygen sensor after the catalytic converter on the side of the engine with cylinder 1. On a four-cylinder there's only one bank, so it's simply the rear sensor, usually reached from under the car.
Will P0038 clear itself?
If a connector was loose or wet and is now making good contact, the light can go off after several drives. A burned-out heater or a short won't fix itself.
References
- NHTSA ODI complaints flat file (FLAT_CMPL)
- NHTSA manufacturer communications / technical service bulletins flat files
- 40 CFR 86.1806-17: Onboard diagnostics (EPA OBD requirements, incl. oxygen sensor monitoring)
- 13 CCR 1968.2: Malfunction and diagnostic system requirements (California OBD II, incl. sensor heater monitoring)