P0136: O2 Sensor Circuit Low Voltage (B1S2)
Severity: low
What it means: The oxygen sensor at bank 1 sensor 2 (downstream) circuit isn't working properly.
Safe to drive? Usually drivable, but fuel economy and emissions can suffer. Get it checked.
Common symptoms
- Check-engine light
- Possible worse fuel economy
- Possible rough running
Likely causes, ranked
- Failing oxygen sensor$254DIY
CarMD 2024 national average about $254
- Wiring damage or connector corrosionDIY
- Exhaust leak near the sensorShop
- Fuel mixture problem that the sensor is correctly reportingShop
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What it means: The oxygen sensor at bank 1 sensor 2 (downstream) circuit isn't working properly.
Severity: Low. Safe to drive? Usually drivable, but fuel economy and emissions can suffer. Get it checked.
DIY or shop?
An O2 sensor swap with a sensor socket is commonly 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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