Failed heater element inside the Bank 1 Sensor 3 oxygen sensor; Damaged, chafed or corroded wiring to the sensor heater, including short or open circuits; Poor connection at the sensor plug or a loose or corroded terminal; Blown fuse or faulty relay supplying the heater circuit (on models where the heater has a separate supply); Exhaust heat or road debris damage to the harness near the sensor; Faulty heater driver in the engine control unit, or an outdated calibration where the manufacturer has issued a fix.

P0147

O2 Sensor Heater Circuit Bank 1 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
47: FaultThe specific fault in that area

What it means

P0147 means the control unit has found a fault in the heater circuit of the oxygen sensor at Bank 1, Sensor 3. This sensor sits further downstream than the usual post-catalyst sensor, and few engines have one. The control unit monitors the heater's current or its driver circuit and sets the code when the readings fall outside the expected range, or the heater does not bring the sensor up to temperature in the expected time. Which sensor is Sensor 3 depends on the vehicle, so confirm its position for the model before testing.

Symptoms

Engine management light on
Usually no change in driveability
Possible slightly slower closed-loop catalyst monitoring
Other oxygen sensor heater or catalyst monitor codes stored alongside
Failed emissions test or readiness monitors not completing

Possible causes

Failed heater element inside the Bank 1 Sensor 3 oxygen sensorlikely
Damaged, chafed or corroded wiring to the sensor heater, including short or open circuitslikely
Poor connection at the sensor plug or a loose or corroded terminalpossible
Blown fuse or faulty relay supplying the heater circuit (on models where the heater has a separate supply)possible
Exhaust heat or road debris damage to the harness near the sensorpossible
Faulty heater driver in the engine control unit, or an outdated calibration where the manufacturer has issued a fixrare

How to diagnose

Read all stored codes and freeze frame data, and note whether other heater or oxygen sensor codes are present.
Check the vehicle's documentation to identify which sensor is Bank 1 Sensor 3 on this model and engine.
Inspect the sensor wiring and plug along its whole length for chafing, melting, contact with the exhaust, water ingress and corrosion.
Check the fuse and relay for the oxygen sensor heater supply, using the wiring diagram for the model.
With the sensor unplugged and the engine off, measure the heater element resistance and compare it with the manufacturer's specification.
Check the heater supply voltage and the ground or control signal at the harness plug with the ignition on, as the wiring diagram specifies.
Test the harness for continuity and for shorts to ground or supply between the sensor plug and the control unit.
Check for any applicable software updates or technical bulletins for the model before condemning the control unit.

How to fix

Replace the Bank 1 Sensor 3 oxygen sensor if the heater element is open circuit or out of specification.
Repair or replace damaged wiring and secure it away from hot or moving parts.
Clean or repair the connector terminals, or replace the connector if it is corroded or loose.
Replace the faulty fuse or relay, and find out why it failed.
Update the control unit calibration only if the manufacturer lists an outdated calibration as a known cause, or repair or replace the control unit if its driver is faulty.

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this fault rarely affects safety or causes engine damage. Get it diagnosed soon, as the fault will stop the catalyst monitor completing and may cause an emissions test failure.

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