P015C
O2 Sensor Delayed Response - Rich to Lean Bank 2 Sensor 1.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 1
- AreaFuel and air metering
- 5C
- FaultThe specific fault in that area
What it means
P015C is the generic code for a delayed response from the upstream oxygen (air-fuel ratio) sensor on Bank 2, Sensor 1 when the mixture changes from rich to lean. The engine control unit monitors how quickly the sensor signal reacts after a switch from rich to lean and set the code because the response was slower than expected. Bank 2 is the side of the engine that does not contain cylinder number 1.
Symptoms
- Engine warning light on
- Poor fuel economy
- Slightly rough running or uneven idle
- Hesitation or reduced performance under load
- Raised exhaust emissions or a failed emissions test
- Possible fuel trim codes stored alongside
Possible causes
- Ageing or contaminated Bank 2 Sensor 1 (slow to react due to wear, soot, oil, coolant or silicone contamination)likely
- Damaged wiring, poor connector contact or corrosion in the Bank 2 Sensor 1 circuitlikely
- Exhaust leak upstream of or near the sensor letting in false air and distorting readingspossible
- Sensor heater circuit fault, so the sensor is not reaching or holding operating temperaturepossible
- Fuelling or air metering problem on Bank 2 such as a vacuum leak, leaking injector or fuel pressure faultpossible
- Engine misfire or oil or coolant burning, contaminating the sensorrare
- Faulty engine control unit or outdated software (only where the manufacturer has a known issue for the model)rare
How to diagnose
- Read all stored and pending codes and note the freeze frame data (engine temperature, load, speed, fuel trims) to see when the fault occurred.
- Check for other codes, especially misfires, fuel trim, heater circuit or other oxygen sensor codes, and deal with those first.
- Visually inspect the Bank 2 Sensor 1 wiring and connector for chafing, heat damage, water ingress, corrosion and bent or loose pins.
- Inspect the exhaust manifold, flexible joints and pipework before the sensor for leaks, and check for intake or vacuum leaks on Bank 2.
- With live data, watch the Bank 2 Sensor 1 signal and short and long term fuel trims at idle and steady load, comparing with Bank 1 to see whether the response is slow.
- Check the sensor heater circuit supply, earth and resistance against the manufacturer's specification for the model.
- Check fuel pressure, injector condition and for signs of oil or coolant consumption if the sensor looks contaminated.
- Check whether the manufacturer has a software update or technical bulletin for this code on the specific model and engine.
How to fix
- Repair or replace damaged wiring, terminals or connectors in the sensor circuit.
- Replace the Bank 2 Sensor 1 oxygen sensor if it is confirmed slow, contaminated or has a failed heater.
- Repair any exhaust leak near the sensor and renew faulty gaskets or joints.
- Fix any vacuum leak, fuel delivery or injector fault found on Bank 2.
- Correct the source of contamination, such as an oil or coolant leak into the engine, before fitting a new sensor.
- Apply a manufacturer software update only if a calibration issue is a known cause for the vehicle.
Can I keep driving?
The car can usually be driven for a short time, but have it checked soon as poor mixture control can raise fuel use and emissions and may eventually harm the catalytic converter. If the car runs badly or misfires, limit driving until it is repaired.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.