P0155: O2 Sensor Heater Circuit Malfunction (B2S1)
Severity: low
What it means: The heater circuit inside the oxygen sensor at bank 2 sensor 1 isn't working. The heater helps the sensor reach operating temperature quickly.
Safe to drive? Yes, generally safe to drive.
Common symptoms
- Check-engine light
- Possibly slightly worse fuel economy
Likely causes, ranked
- Failed heater inside the O2 sensor (sensor replaced)$254DIY
CarMD 2024 national average about $254
- Blown fuse or wiring faultDIY
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What it means: The heater circuit inside the oxygen sensor at bank 2 sensor 1 isn't working. The heater helps the sensor reach operating temperature quickly.
Severity: Low. Safe to drive? Yes, generally safe to drive.
DIY or shop?
Check the fuse, then replace the sensor. Usually DIY.
Before you replace parts
- Read all stored codes and freeze-frame data. Fix misfire, fuel or sensor codes before chasing emissions codes.
- Check the simple things first: connectors, vacuum hoses, fluid levels and the gas cap.
- Clear the code only after a repair, then confirm it stays off after a few drives.
- Check your VIN for recalls and service bulletins.
Safety / mechanic note
Generally not urgent, but a code only points to a system, not always a specific part. Verify with a mechanic before buying expensive parts.
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