Faulty heater element inside the Bank 1 Sensor 3 oxygen sensor; Heater control wiring shorted to a voltage supply or chafed against other wiring; Damaged, corroded or contaminated connector at the sensor or in-line plug; Heater supply or relay fault feeding the sensor heater circuit; Exhaust or heat damage to the sensor wiring near the sensor; Fault in the control unit heater driver.

P0044

HO2S Heater Control Circuit High 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
0: AreaFuel and air metering, auxiliary emission controls
44: FaultThe specific fault in that area

What it means

P0044 means the control unit has detected a high voltage or high-side fault in the heater control circuit of the Bank 1 Sensor 3 heated oxygen sensor, which is the third sensor downstream on the bank 1 side of the exhaust. The unit monitors the heater driver and sets the code when the circuit state does not match the commanded state, typically from a short to voltage or a driver fault. Sensor 3 is only fitted on some engines and exhaust layouts, so its exact position depends on the model.

Symptoms

Engine warning light on
Usually no noticeable change in driving
Possible slight rise in emissions readings at test
Other oxygen sensor or catalyst monitor codes stored alongside
Readiness monitors for the oxygen sensor heater or sensor not completing

Possible causes

Faulty heater element inside the Bank 1 Sensor 3 oxygen sensorlikely
Heater control wiring shorted to a voltage supply or chafed against other wiringlikely
Damaged, corroded or contaminated connector at the sensor or in-line plugpossible
Heater supply or relay fault feeding the sensor heater circuitpossible
Exhaust or heat damage to the sensor wiring near the sensorpossible
Fault in the control unit heater driverrare

How to diagnose

Read all stored codes and freeze frame data, and note whether other oxygen sensor codes are present.
Confirm from the vehicle's documentation which sensor is Bank 1 Sensor 3 on this model and engine.
Visually inspect the sensor wiring and connector for heat damage, chafing, melted insulation, water ingress and corrosion.
Check the heater supply voltage and earth or control signal at the sensor connector against manufacturer data.
Measure the heater element resistance at the sensor and compare with the specification for that model.
Check the wiring between the sensor and control unit for a short to voltage, and check related fuses and relays.
Clear the code, run the car through a drive cycle and watch the heater control and sensor data to see if the fault returns.

How to fix

Replace the Bank 1 Sensor 3 oxygen sensor if the heater element is out of specification.
Repair or replace damaged wiring, correcting any short to voltage and securing the loom away from heat and sharp edges.
Clean or replace the corroded or damaged connector and terminals.
Replace a faulty relay or repair the heater supply circuit as found.
If all wiring and the sensor test correctly, have the control unit heater driver checked and repaired or replaced per manufacturer guidance.

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as this fault rarely affects driveability. Book it in soon so it does not cause a failed emissions test or hide other faults.

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