O2 Sensor Circuit (Bank 1, Sensor 2)
The P0136 code means the vehicle's onboard diagnostic system has detected: O2 Sensor Circuit (Bank 1, Sensor 2). This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- easy
- Estimated cost
- $50-$200
Test O2 sensor voltage (should fluctuate 0.1-0.9V). Do not replace a $150 sensor without confirming it is actually bad first.
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Shows real-time O2 sensor readings on your phone. See if the sensor is lazy, stuck, or actually working before spending money.
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Common Symptoms
- Check Engine Light on
- Emissions test failure
- Possible false P0420 trigger
- Slight fuel economy change
Probable Causes (Ranked by Likelihood)
- Failed downstream O2 sensor Very High
- Wiring damage or connector corrosion High
- Sensor heater failure Moderate
- Exhaust leak near downstream sensor Low
Step-by-Step Diagnostic Procedure
-
Monitor Bank 1 Sensor 2 voltage. At steady highway speed it should show a slow, mostly steady signal around 0.6-0.7V.
-
If signal is erratic or shows no voltage, check wiring and connector.
-
Test heater circuit resistance.
-
Replace sensor if confirmed faulty.
Common Fixes by Vehicle
What techs usually find when diagnosing P0136 on specific vehicles — tap your vehicle for the fix and the exact part:
2007-2017 Toyota Camry/Corolla 2.5L Easy DIY
Bank 1 Sensor 2 (downstream) O2 sensor circuit malfunction. The sensor monitors catalytic converter efficiency. Replace with Denso 234-4350. Before replacing, check for exhaust leaks between the cat and the sensor. Also check the sensor wiring for heat damage from the catalytic converter. If P0420 is also present, the cat may be failing.
Labor: 30 min2009-2020 Ford F-150/Explorer 3.5L/5.0L Easy DIY
Bank 1 downstream O2 sensor malfunction. Check the sensor connector for heat damage -- it sits close to the catalytic converter. Test the sensor heater resistance (should be 4-8 ohms). If the heater is open, replace with Motorcraft DY-1178. Also check for exhaust leaks at the cat-to-pipe connection that can contaminate the sensor reading.
Labor: 30-45 min2008-2019 Honda Accord/CR-V 2.4L Easy DIY
Downstream O2 sensor circuit malfunction. Honda downstream sensors last about 120-150K miles. Replace with Denso 234-4350. Check the sensor wiring near the catalytic converter for melted insulation. Also inspect the exhaust pipe gasket at the sensor location for leaks. Apply anti-seize to the sensor threads before installation.
Labor: 30 minFrequently Asked Questions
Will a bad downstream O2 sensor cause P0420?
Yes. A lazy or slow downstream sensor mimics the waveform signature of a failed catalytic converter. Always replace or test the downstream sensor before buying a catalytic converter.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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