Faulty Bank 1 Sensor 4 oxygen sensor (failed element or heater); Damaged, chafed or corroded wiring to the sensor; Poor connection or water ingress at the sensor plug; Exhaust leak near the sensor affecting its reading; Blown fuse or faulty power or earth supply to the sensor circuit; Sensor contaminated by oil, coolant or silicone; Fault in the engine control unit.

P01F5

O2 Sensor Circuit No Activity Detected 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
F5: FaultThe specific fault in that area

What it means

P01F5 is a generic powertrain code meaning the engine control unit has detected no activity from the oxygen sensor circuit on Bank 1, Sensor 4. Sensor 4 is an additional downstream sensor, and its position depends on the exhaust layout of the particular engine. The control unit set the code because the signal stayed flat, absent or out of its expected range when the sensor should have been responding.

Symptoms

Engine management light on
Usually no noticeable change in driving
Possible slight rise in fuel consumption on some models
Other oxygen sensor or catalyst monitor codes stored alongside
Failed emissions test or monitor not completing

Possible causes

Faulty Bank 1 Sensor 4 oxygen sensor (failed element or heater)likely
Damaged, chafed or corroded wiring to the sensorlikely
Poor connection or water ingress at the sensor pluglikely
Exhaust leak near the sensor affecting its readingpossible
Blown fuse or faulty power or earth supply to the sensor circuitpossible
Sensor contaminated by oil, coolant or siliconepossible
Fault in the engine control unitrare

How to diagnose

Read all stored codes and freeze frame data, noting engine temperature, load and mileage when the fault set
Check the vehicle-specific exhaust layout to confirm where Bank 1 Sensor 4 is fitted, as this varies by model and engine
Inspect the sensor, wiring and plug for heat damage, chafing, corrosion, water and loose terminals
Check for exhaust leaks near the sensor and along the pipework upstream of it
Check the relevant fuses and the sensor's power and earth supplies against the manufacturer's wiring diagram
With a scan tool, watch the live sensor signal and compare it with the other oxygen sensors on warm-up and under varied load
Test the sensor heater circuit resistance and signal wire continuity to the control unit, to the manufacturer's specification
Clear the code and road test to confirm it does not return

How to fix

Repair or replace damaged wiring and terminals in the sensor circuit
Clean, dry and reseat the connector, replacing it if corroded or damaged
Replace the Bank 1 Sensor 4 oxygen sensor if it is faulty or contaminated
Repair any exhaust leak affecting the sensor
Restore the fuse, power or earth supply if faulty, after finding why it failed
Find and repair the source of any contamination, such as oil or coolant ingress, before fitting a new sensor

Can I keep driving?

Low severity

The car can normally be driven while you book a repair, as this fault usually has little effect on driveability. Do not leave it for long, because it can hide other emissions faults and may cause an MOT failure.

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