P0136: O2 Sensor Circuit — Bank 1 Sensor 2
What to do
No noticeable driveability impact, but the catalyst monitor cannot complete and the car will not pass an emissions test.
What this code means
A signal circuit fault in the downstream bank 1 sensor, positioned after the catalytic converter. This sensor does not trim fuelling — its job is to watch the converter's output and grade how well it is working. A fault here costs the catalyst monitor rather than driveability, which is why the car usually feels entirely normal while the code is stored.
Likely causes
Start here
- Faulty oxygen sensor · easy
- Corroded or loose connector · easy
- Road damage to underfloor wiring · moderate
Less common
- Exhaust leak before the sensor · moderate
- Open circuit in sensor wiring · moderate
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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