Faulty oxygen sensor (Bank 1 Sensor 4), through age, contamination or internal failure; Damaged, chafed, melted or corroded sensor wiring or connector; Exhaust leak near the sensor affecting the reading; Blown fuse or fault in the sensor heater power supply or ground; Sensor contaminated by oil, coolant or silicone sealant; Fault in the engine control unit or the sensor control module (depends on model).

P01F1

O2 Sensor Circuit Bank 1 Sensor 4.

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
F1: FaultThe specific fault in that area

What it means

P01F1 is a generic code for a fault in the oxygen sensor circuit for Bank 1, Sensor 4. Bank 1 is the side of the engine with cylinder number one. Sensor 4 is the fourth oxygen sensor along that exhaust path, so it only appears on certain exhaust layouts, and which sensor it is depends on the model and engine. The control unit set the code because the signal or circuit for that sensor was outside its expected range or behaviour. The exact test that failed (voltage, heater or response) is not stated by the code title, so check the freeze frame and any related codes.

Symptoms

Engine management light on
No noticeable change in driving in many cases
Possible slight rise in fuel consumption
Failed emissions test or readiness monitors not completing
Other oxygen sensor or catalyst efficiency codes stored alongside

Possible causes

Faulty oxygen sensor (Bank 1 Sensor 4), through age, contamination or internal failurelikely
Damaged, chafed, melted or corroded sensor wiring or connectorlikely
Exhaust leak near the sensor affecting the readingpossible
Blown fuse or fault in the sensor heater power supply or groundpossible
Sensor contaminated by oil, coolant or silicone sealantpossible
Fault in the engine control unit or the sensor control module (depends on model)rare

How to diagnose

Confirm which physical sensor is Bank 1 Sensor 4 on this model and engine using the manufacturer's data, as layouts vary.
Read all stored and pending codes and note the freeze frame data, including engine load, temperature and fuel trims.
Visually inspect the sensor, wiring and connector along the full length for heat damage, chafing, water ingress or corrosion.
Check for exhaust leaks around the sensor and upstream of it, and for any sign of fuel, oil or coolant contamination.
Check the relevant fuses and relays for the sensor heater supply.
With a scan tool, view live sensor data and see if the signal responds sensibly to changes in throttle and fuel trim, or sits fixed.
Test the sensor circuit for supply, ground, signal continuity and shorts, and measure heater resistance to the manufacturer's specification.
Clear the code and road test to see if it returns, checking readiness monitors afterwards.

How to fix

Repair or replace damaged wiring and connectors, and secure the harness away from hot or moving parts.
Replace the faulty oxygen sensor with a correct specification part.
Repair any exhaust leak near the sensor.
Replace the blown fuse after finding and fixing the cause of the overload.
Fix the source of any contamination (such as oil or coolant ingress) before fitting a new sensor.
If all wiring and the sensor test fine, have the control unit checked and any outdated calibration addressed per the manufacturer.

Can I keep driving?

Low severity

The car can usually be driven normally in the short term, but book it in for diagnosis soon. If other faults such as misfires appear or the car runs poorly, have it checked sooner.

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