P0044 — Oxygen sensor heater control circuit high — bank 1, sensor 3

P0044 indicates an abnormally high electrical level in the heater control circuit for bank 1, sensor 3. This is the third sensor on this bank; its exact position depends on the multi-sensor exhaust layout. “High” concerns electrical control, not a rich mixture or exhaust temperature. Supply wiring and heater control strategies differ between vehicles.

Affected system: Powertrain

Symptoms

• Engine warning lamp and a stored code.
• The vehicle may drive normally while emissions monitoring remains incomplete.

Possible causes

• Short to supply or between wires near the exhaust.
• Incorrect or internally faulty heater; a control circuit fault is also possible.

What to check

• Confirm B1S3 in the engine diagram and save related codes and freeze-frame data before clearing anything.
• With the exhaust cold, inspect the B1S3 harness for melted insulation, rubbing, water in the connector and loose terminals.
• Check whether the controlled wire is accidentally connected to supply; interpret voltage or excess current using the OEM circuit information.
• Test element resistance and control response separately using suitable equipment; do not apply voltage directly to unidentified pins.
• After correcting the confirmed fault, repeat the OEM monitor conditions and check for code recurrence, beyond merely extinguishing the lamp.

Also written as: P0044-00, P004400, PO044 (some scan tools add the fault-type byte, e.g. -00).