P0136: O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
Key takeaways
- P0136 means the engine computer doesn't like the signal from the downstream oxygen sensor on bank 1, the one after the catalytic converter.
- It's safe to drive on most cars, because the downstream sensor checks the converter rather than controlling the fuel mixture.
- Damaged wiring, a corroded connector or an exhaust leak ahead of the sensor are worth ruling out before buying a $150–$400 sensor.
- Most fixes cost $100–$600 at an independent shop, and the cheap ones are the common ones.
- 5 owner complaints filed with NHTSA mention P0136, and 4 manufacturer bulletins, from Jaguar and Land Rover, name it.
What P0136 means
The oxygen sensor behind your catalytic converter is sending a signal the engine computer can’t use. Scanners call it “O2 Sensor Circuit Malfunction (Bank 1 Sensor 2).” Bank 1 is the side of the engine with cylinder 1 (a four-cylinder has only bank 1), and sensor 2 is the downstream sensor after the converter. Its job is to show the computer how well the converter is cleaning the exhaust. A healthy downstream sensor holds a fairly steady voltage in the middle of its range. When the signal is out of range, missing, or doesn’t respond the way the computer expects, it sets P0136.
Is it safe to drive?
Yes. On most cars the downstream sensor only watches the converter; it doesn’t decide how much fuel the engine gets, so the car drives normally. Book a repair in the next few weeks, since a lit check engine light fails emissions inspections in most states and hides any new code.
The answer changes if the car also runs rough, the light flashes, or you get upstream or fuel codes such as P0171. Then the problem is bigger than this sensor and needs a look soon.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Exhaust leak ahead of the sensor | Ticking or puffing at a joint, soot at the converter flange or flex pipe; smoke test of the exhaust | $150–$600 |
| Damaged wiring or corroded connector | Wire melted on the exhaust, snagged or chewed, green corrosion or water in the plug; signal changes when the harness is moved | $100–$250 |
| Failed or worn-out sensor | Circuit tests good but the signal is dead, erratic or stuck in live data | $150–$400 |
| Oil or coolant fouling the sensor | Oily or chalky deposits on the tip; an oil leak dripping on the exhaust above it | $150–$400 for the sensor, plus fixing the leak |
| Engine computer software (some makes) | A bulletin for your exact model and year names P0136 | $100–$200, often $0 under warranty or a bulletin |
Trucks and sensors rusted into the pipe land at the top of these ranges.
What to check first
- Read every stored code. P0136 with the heater code P0141 points at the sensor or its harness. P0136 with P0137 or P0138 narrows it to a low or high signal.
- Inspect the harness under the car. Look for wires touching the exhaust, a broken clip, rodent damage, or water and corrosion in the connector.
- Check for exhaust leaks between the engine and the sensor, including the converter flanges. Outside air pulled in at a leak confuses the reading.
- Watch the sensor on a scan tool at warm idle and at 2,500 rpm, next to the upstream sensor. A dead or erratic downstream signal with good wiring means the sensor.
- Replace the sensor last, then clear the code and drive a few days of mixed trips to confirm it stays off.
- Check bulletins. The only makes with P0136 bulletins are Jaguar and Land Rover, covering heated oxygen sensor codes on the 2013–2015 XF, 2015–2016 F-Type and 2016 Range Rover.
5 owner complaints filed with NHTSA mention P0136, each on a different model, so no single car stands out.
What it costs
The cheap outcome is a wiring or connector repair at $100–$250. The common outcome is a new downstream sensor at $150–$400. The expensive outcome is an exhaust leak at a flange or flex pipe, $150–$600. An hour of diagnosis, usually $100–$180, tells you whether it’s the wiring, a leak or the sensor before you buy parts. Our O2 sensor guide covers the whole sensor family.
Related codes
P0136 often shows with P0137 (low voltage), P0138 (high voltage), P0139 (slow response) or P0141 (heater), all for the same sensor. If P0420 sets as well, fix P0136 first, because the converter test relies on this sensor. If the car feels fine otherwise, see check engine light on but the car runs fine.
What owners report to NHTSA
5 complaints filed with NHTSA mention P0136, 4 of them since 2015, across 5 different models. The component owners most often filed it under: engine and engine cooling:exhaust system:emission control .
Manufacturer service bulletins that name P0136
4 technical service bulletins and manufacturer communications filed with NHTSA mention P0136, from 2 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- JAGUAR F-TYPE (2015, 2016), bulletin 10097084: "ISSUE: THE CUSTOMER MAY OBSERVE A MIL IN THE INSTRUMENT CLUSTER RELATING TO THE ENGINE SYSTEM (CHECK ENGINE LIGHT) AND ONE OR MORE CODES STORED IN THE PCM RELATING TO HEATED OXYGEN SENSOR (HO2S) IN THE EXHAUST SYSTEM. T…
- LAND ROVER RANGE ROVER (2016), bulletin 10105881: "ISSUE: THE CUSTOMER MAY OBSERVE A MIL IN THE INSTRUMENT CLUSTER RELATING TO THE ENGINE SYSTEM (CHECK ENGINE LIGHT) AND ONE OR MORE CODES STORED IN THE PCM RELATING TO HEATED OXYGEN SENSOR (HO2S) IN THE EXHAUST SYSTEM. T…
- JAGUAR XF (2013, 2014, 2015), bulletin 10096822: "SITUATION: THE ENGINE MALFUNCTION INDICATOR LAMP (MIL) MAY BE ILLUMINATED. UPON DIAGNOSIS, THE TECHNICIAN MAY FIND DIAGNOSTIC TROUBLE CODES (DTC) RELEVANT TO THE MID-CATALYST AND POST-CATALYST HEATED OXYGEN SENSORS (HO2…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
Can I drive with a P0136 code?
Yes, on most cars. The downstream sensor mainly checks the catalytic converter, so the engine runs the same. Fix it before your next emissions test, because the lit light fails the inspection and hides any new code that sets.
Where is bank 1 sensor 2?
It's the oxygen sensor after the catalytic converter on the side of the engine with cylinder 1. On a four-cylinder there's only one bank, so it's simply the rear sensor, usually reached from under the car.
Is P0136 a bad catalytic converter?
Usually not. A tired converter normally sets P0420. P0136 is about the sensor's circuit or signal, which points to the sensor, its wiring, or outside air leaking into the exhaust ahead of it.
Will a new O2 sensor fix P0136?
Often, but check the wiring first. The downstream harness runs under the car where it gets heat, water and road salt, and a corroded plug sets the same code with a new sensor.