P0038 Oxygen sensor heater control circuit high (bank 1, sensor 2)
What P0038 means
The engine computer sees a voltage that is too high in the heater control circuit of the downstream oxygen sensor on bank 1. Typically the control wire is shorted to a power source or the heater element has gone open, so the computer cannot regulate the heater.
P0038 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 80–350 €
- Workshop time
- 0.5–1.5 h
- Repair difficulty
- Easy
- DIY possible
- Yes
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on
- Car usually drives normally
- Catalyst readiness monitor not completing
- Possible failed emissions test
Common causes
- Failed (open) heater element in the downstream oxygen sensor
- Heater control wire shorted to battery voltage
- Melted harness where heater and other wires touch the exhaust
- Engine control unit heater driver fault (rare)
Can I keep driving with P0038?
You can keep driving, but book a repair within a week or two. It does not harm the engine, but the car is likely to fail an emissions test.
What to check first
- Inspect the downstream sensor harness for melted or fused wires near the exhaust.
- Measure the heater resistance at the sensor connector and compare it with the specification.
- With the sensor unplugged, check the control wire for a short to battery voltage.
- If the wiring is sound and the heater is open or out of specification, replace the downstream oxygen sensor.
Related codes
- P0037 Oxygen sensor heater control circuit low (bank 1, sensor 2)
- P0036 Oxygen sensor heater control circuit (bank 1, sensor 2)
- P0030 Oxygen sensor heater control circuit (bank 1, sensor 1)
- P0045 Turbocharger/supercharger boost control A circuit/open
- P0021 Intake (A) camshaft timing over-advanced or system performance (bank 2)
- P0020 Intake (A) camshaft position actuator circuit/open (bank 2)
- P0019 Crankshaft/camshaft position correlation, bank 2 sensor B (exhaust)
- P0018 Crankshaft/camshaft position correlation, bank 2 sensor A (intake)
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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