P0038 means HO2S Heater Control Circuit High (Bank 1 Sensor 2). The computer has found the heater control circuit for the bank 1 sensor 2 oxygen sensor, after the catalytic converter, reading high voltage, so the sensor may not warm up quickly. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0038 means
Oxygen sensors measure the oxygen left in the exhaust. Sensor 1 sits before the catalytic converter and is used for fuel control; sensor 2 sits after it and mainly monitors the converter. Most sensors have a heater so they start working soon after a cold start. A traditional zirconia sensor switches between about 0.1 volt (lean) and 0.9 volt (rich); many newer upstream sensors are wide-band air-fuel sensors that report differently, so check which type your engine uses.
P0038 symptoms
- Check engine light
- Slower warm-up of fuel control after a cold start
- Possible poor fuel economy
Common causes of P0038
- Open heater circuit or blown heater fuse
- Failed oxygen sensor heater
- Unplugged or corroded connector
How to diagnose P0038
- Check the oxygen sensor heater fuse
- Measure heater resistance at the sensor connector
- Check power and the control circuit to the heater
- Inspect wiring near the exhaust
Can you drive with P0038?
Usually yes; fix it to restore normal fuel control and emissions readiness.
P0038 tips
An unplugged downstream sensor after exhaust work is a common cause; check that the connector is latched and clipped away from the pipe.
Will P0038 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0038 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0141 | O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) |
| P0037 | HO2S Heater Control Circuit Low (Bank 1 Sensor 2) |
| P0030 | HO2S Heater Control Circuit (Bank 1 Sensor 1) |
Guides that help
When it is more than a sensor
Oxygen sensor codes are fixed with a sensor, wiring, a fuse or an exhaust leak repair. An engine burning oil or coolant contaminates sensors quickly; if new sensors keep failing, check for blue or white exhaust smoke and a head gasket leak, and compare engines by code on our engines page if the engine is worn out.
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