P0136: O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)
Updated November 7, 2026
Sensor 2 is the oxygen sensor after the catalytic converter on bank 1. It mainly checks how well the converter is working. P0136 means its signal is stuck, missing or outside the range the computer expects.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- A failed downstream oxygen sensor
- Damaged wiring or a corroded connector (it sits low, near hot exhaust and road debris)
- A signal wire shorted to ground or to voltage
- An exhaust leak near the sensor, which can make it read lean
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Check engine light
- Usually no change in how the car drives
- Emissions readiness monitors may not complete, causing a failed inspection
Is it safe to drive?
Generally safe to drive with a steady light, but get it fixed; the computer can't confirm the catalytic converter is working, and the car may fail inspection.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Check for other O2 or heater codes such as P0141; a heater fault can affect the signal.
- With the engine fully warm, watch sensor 2 voltage in live data. Downstream sensors are almost always regular (narrowband) sensors that read about 0.1 to 0.9 volts; a reading that stays stuck at one value (often near 0 volts) and doesn't move at all when you raise the engine speed and then let off points to the sensor or wiring.
- Inspect the wiring and connector for melting or chafing, and look for exhaust leaks near the sensor. Let the exhaust cool before touching it.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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Questions
What does P0136 mean?
P0136 is the generic OBD2 code for "O2 Sensor Circuit Malfunction (Bank 1, Sensor 2)." Sensor 2 is the oxygen sensor after the catalytic converter on bank 1. It mainly checks how well the converter is working. P0136 means its signal is stuck, missing or outside the range the computer expects.
Is it safe to drive with P0136?
Generally safe to drive with a steady light, but get it fixed; the computer can't confirm the catalytic converter is working, and the car may fail inspection.
How do I check P0136 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Check for other O2 or heater codes such as P0141; a heater fault can affect the signal. With the engine fully warm, watch sensor 2 voltage in live data. Downstream sensors are almost always regular (narrowband) sensors that read about 0.1 to 0.9 volts; a reading that stays stuck at one value (often near 0 volts) and doesn't move at all when you raise the engine speed and then let off points to the sensor or wiring. Inspect the wiring and connector for melting or chafing, and look for exhaust leaks near the sensor. Let the exhaust cool before touching it.
Related codes
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