Emission controls · Powertrain · generic (SAE-defined)
P0136: O2 Sensor Circuit (Bank 1 Sensor 2)
P0136 means the engine computer found a general fault in the downstream oxygen sensor circuit on bank 1, the sensor located after the catalytic converter.
Standard title per SAE J2012 / ISO 15031-6 · Updated 2026-11-07 · By CarWhere Research
How P0136 sets
The powertrain control module (PCM) uses the bank 1 sensor 2 oxygen (O2) sensor, mounted after the catalytic converter, to judge how well the converter stores and releases oxygen. Some systems also use it for small fuel trim corrections. If the signal is electrically faulty, out of range or implausible under steady warm conditions, the PCM sets P0136. Limits are manufacturer-specific.
Common causes of P0136
Roughly most likely first; the actual cause depends on the vehicle and needs testing to confirm.
- Failed bank 1 sensor 2 oxygen sensor
- Damaged wiring from road debris or exhaust heat
- Corroded connector, often from road salt and water
- Exhaust leak near the downstream sensor
- Signal circuit shorted to the heater circuit
P0136 symptoms
- Check engine light on
- Usually no drivability symptoms
- Possible failed emissions test or incomplete catalyst monitor
How P0136 is diagnosed
- Scan for codes and freeze frame; note any catalyst efficiency or heater codes.
- Locate the sensor after the catalytic converter on the cylinder 1 side and inspect its wiring and connector underneath the vehicle.
- Check for exhaust leaks around the converter flanges and sensor bung.
- With the engine warm, watch live data; a downstream sensor behind a healthy converter normally shows a fairly steady reading.
- Test signal, ground and heater circuits for opens and shorts.
Typical fixes for P0136
- Replace the bank 1 sensor 2 oxygen sensor
- Repair damaged wiring or replace a corroded connector
- Repair exhaust leaks near the sensor
Replace parts only after testing confirms the cause — a code names the circuit or condition that failed a check, not necessarily the faulty part. We don’t publish per-repair prices; for what households actually spend on upkeep, see car repair costs.
Related codes & warning lights
P0136 FAQ
What does code P0136 mean?
P0136 means the engine computer found a general fault in the downstream oxygen sensor circuit on bank 1, the sensor located after the catalytic converter. The standard definition is "O2 Sensor Circuit (Bank 1 Sensor 2)."
Can I drive with a P0136 code?
Yes, typically. The downstream sensor mainly checks catalytic converter performance rather than controlling fuel, so drivability is usually unaffected, but the car will likely fail an emissions inspection until it is repaired.
What does the bank 1 sensor 2 oxygen sensor do?
It sits after the catalytic converter and lets the engine computer verify that the converter is cleaning the exhaust. Some vehicles also use it to make small corrections to fuel control.
Can P0136 cause a catalytic converter code?
A faulty downstream sensor can produce misleading converter readings, so it is best to fix P0136 before condemning the converter for a P0420.
Keep researching
More emission controls codes
Sources
- SAE J2012 — Diagnostic Trouble Code Definitions (standard code titles)
- ISO 15031-6 — Road vehicles: communication between vehicle and external equipment for emissions-related diagnostics, Part 6: Diagnostic trouble code definitions
- U.S. EPA — Vehicle Emissions Inspection and Maintenance (I/M) programs
- U.S. EPA, 40 CFR 86.1806-17 — Federal onboard diagnostics requirements for light-duty vehicles
- California Air Resources Board — On-Board Diagnostic (OBD) Program
General information written by CarWhere Research, not a diagnosis of your vehicle. Manufacturers can add their own sub-definitions and test conditions; confirm with the factory service information for your year, make and model. Before paying for a repair, check NHTSA for open recalls and your warranty booklet: federal law requires an emissions warranty on major emission-control parts such as the catalytic converter and engine computer.