Faulty or aged Bank 2 Sensor 3 oxygen sensor giving a constantly low signal; Damaged, chafed or heat-affected sensor wiring shorting to earth; Corroded, loose or contaminated connector terminals at the sensor or harness plug; Exhaust leak near the sensor letting in air and skewing the signal; Sensor contaminated by coolant, oil or fuel additives; Fault in the sensor heater or reference circuit supply, depending on model; Fault inside the engine control unit.

P0163

O2 Sensor Circuit Low Voltage Bank 2 Sensor 3.

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
63: FaultThe specific fault in that area

What it means

P0163 means the control unit has detected a low voltage signal in the circuit of the oxygen sensor fitted at Bank 2, Sensor 3. This is normally the sensor downstream of the second catalyst or further back in the exhaust, and it is only fitted on some vehicles. The code sets when the signal voltage stays below the expected range, which points to a sensor fault, a wiring fault or an exhaust leak affecting the reading.

Symptoms

Engine warning light on
Usually no noticeable change in driving
Possible slight rise in fuel consumption on some vehicles
Other oxygen sensor or catalyst codes stored alongside
Failed emissions test

Possible causes

Faulty or aged Bank 2 Sensor 3 oxygen sensor giving a constantly low signallikely
Damaged, chafed or heat-affected sensor wiring shorting to earthlikely
Corroded, loose or contaminated connector terminals at the sensor or harness plugpossible
Exhaust leak near the sensor letting in air and skewing the signalpossible
Sensor contaminated by coolant, oil or fuel additivespossible
Fault in the sensor heater or reference circuit supply, depending on modelrare
Fault inside the engine control unitrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including engine temperature, load and fuel trims.
Confirm which sensor is Bank 2 Sensor 3 on this specific model and engine, as the layout varies, using the manufacturer's information.
Visually inspect the sensor, its wiring and the connector for chafing, melting, corrosion, water ingress or damage.
Check the exhaust around and ahead of the sensor for leaks, cracks or blown gaskets.
With a scan tool, watch the live sensor voltage at warm idle and when revving, and see whether it is stuck low or responds.
Check the sensor signal and earth wires for continuity and for shorts to earth, and measure the reference supply where applicable, following the model's wiring diagram.
Check for other faults such as misfires, fuel trim problems or coolant or oil consumption that could contaminate the sensor.
Clear the code after repair and road test to confirm it does not return.

How to fix

Repair or replace damaged wiring or the connector terminals.
Clean and secure the connector, and fix any water ingress.
Replace the Bank 2 Sensor 3 oxygen sensor if it is faulty or contaminated.
Repair any exhaust leak near the sensor.
Fix any underlying engine fault, such as oil or coolant burning, that contaminated the sensor.
Update or correct the control unit software only if the manufacturer lists an outdated calibration as a known cause for this model.

Can I keep driving?

Low severity

The car can normally be driven while you book it in, as this sensor is not usually critical to engine running. Have it checked soon to avoid a failed emissions test and to rule out an underlying fault.

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