Failed or aged downstream oxygen sensor (Bank 1 Sensor 2); Damaged, chafed, burnt or contaminated sensor wiring or connector; Open or high resistance in the sensor heater circuit or its fuse or relay supply, where fitted to this circuit; Exhaust leak near the sensor affecting its reading; Sensor contaminated by oil, coolant or fuel additives from an engine fault; Fault in the engine control unit.

P0136

O2 Sensor Circuit Bank 1 Sensor 2.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
1: AreaFuel and air metering
36: FaultThe specific fault in that area

What it means

P0136 is the generic code for a fault in the oxygen sensor circuit for Bank 1, Sensor 2, which is the sensor downstream of the catalytic converter on the side of the engine with cylinder number one. The engine control unit has seen a signal from this sensor that is out of range, stuck, shorted, open circuit or otherwise not behaving as expected, so it cannot reliably judge catalyst performance.

Symptoms

Engine warning light on
Usually no noticeable change in driving
Slightly poorer fuel economy in some cases
Failed emissions test
Other oxygen sensor or catalyst codes stored alongside

Possible causes

Failed or aged downstream oxygen sensor (Bank 1 Sensor 2)likely
Damaged, chafed, burnt or contaminated sensor wiring or connectorlikely
Open or high resistance in the sensor heater circuit or its fuse or relay supply, where fitted to this circuitpossible
Exhaust leak near the sensor affecting its readingpossible
Sensor contaminated by oil, coolant or fuel additives from an engine faultpossible
Fault in the engine control unitrare

How to diagnose

Read all stored and pending codes and note freeze frame data such as engine temperature, load and speed when the code set
Confirm which sensor is Bank 1 Sensor 2 for this engine, as layout varies by model, and check it is plugged in and secure
Inspect the sensor wiring and connector for chafing, melting, corrosion, water ingress and contact with the exhaust
Look for exhaust leaks between the catalyst and the sensor and around the sensor mounting
Check the live data for the sensor voltage at idle and when warm: a signal stuck high, low or flat suggests a sensor or wiring fault
Check the heater circuit resistance, supply voltage and fuse against the manufacturer's data for the model
Test the signal and earth wires for continuity, short to earth and short to supply with the connector unplugged
Check for engine faults such as oil or coolant burning that could contaminate the sensor

How to fix

Replace the downstream oxygen sensor with a correct specification part if it fails testing
Repair or replace damaged wiring or the connector, including any corroded terminals
Restore the heater circuit supply by repairing the fuse, relay or wiring fault found
Repair any exhaust leak affecting the sensor reading
Fix the underlying engine fault that contaminated the sensor, then replace the sensor if it is damaged

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this fault rarely affects drivability. Do not leave it for long, because it may fail an emissions test and can mask a developing catalyst or engine problem.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.