P00D6
HO2S Sensor Correlation Bank 2 Sensor 1/Bank 2 Sensor 2.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 0
- AreaFuel and air metering, auxiliary emission controls
- D6
- FaultThe specific fault in that area
What it means
P00D6 means the engine control unit has found that the readings from the bank 2 sensor 1 (upstream) and bank 2 sensor 2 (downstream) heated oxygen sensors do not correlate as expected. The control unit compares how the two sensors respond to the exhaust gas and sees a mismatch. The cause can be a sensor, its wiring, an exhaust leak or an engine fault that affects exhaust gas content. Sensor layout and test criteria vary by model and engine.
Symptoms
- Engine management light on
- Poor or uneven fuel economy
- Rough idle or hesitation under load
- Possible smell of fuel or rotten eggs from the exhaust
- Failed emissions test
- Other fuelling or oxygen sensor codes stored alongside
Possible causes
- Faulty, slow or aged bank 2 oxygen sensor (upstream or downstream)likely
- Exhaust leak near the bank 2 manifold, flexible joint or catalytic converter letting in outside airlikely
- Damaged wiring, poor connector contact or corrosion in the bank 2 sensor circuitspossible
- Sensor contamination from oil, coolant, silicone or poor-quality fuelpossible
- Degraded bank 2 catalytic converter changing downstream sensor responsepossible
- Fuelling or misfire fault on bank 2 (vacuum leak, injector fault, ignition fault) skewing exhaust contentpossible
- Wrong sensor type fitted, or sensors swapped between positions or banksrare
How to diagnose
- Read all stored and pending codes and note the freeze frame data (load, engine temperature, fuel trims) from when the fault set.
- Check for related codes such as misfires, fuel trim faults, lean or rich codes or other oxygen sensor codes, and deal with those first.
- Visually inspect the bank 2 sensor wiring, connectors and plugs for chafing, heat damage, water ingress and corrosion.
- Inspect the exhaust from manifold to catalytic converter for leaks, cracks, blown gaskets and loose joints, especially upstream of the sensors.
- Check that the sensors are in the correct positions and are the correct type for the engine.
- With a scan tool, watch live data for both bank 2 sensors at operating temperature and compare their switching speed and voltage against bank 1 and the manufacturer's specification.
- Check sensor heater circuit supply, earth and resistance against the manufacturer's figures for your model.
- Check fuel trims and look for vacuum leaks or injector faults, then assess catalytic converter condition using the manufacturer's test procedure.
How to fix
- Repair or replace damaged wiring or connectors in the bank 2 sensor circuits.
- Repair exhaust leaks, using new gaskets or sections as needed.
- Replace the faulty bank 2 oxygen sensor once testing confirms it is at fault.
- Fix any underlying misfire, vacuum leak or fuelling fault and cure the source of any contamination (oil or coolant consumption).
- Replace the catalytic converter only if testing proves it is degraded and the root cause has been fixed.
- Fit the correct sensor type in the correct position if it was wrong.
Can I keep driving?
The car can usually be driven for a short time, but book it in soon. Fuel economy and emissions may suffer, and an underlying misfire or fuelling fault could damage the catalytic converter if left.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.