P0043 HO2S Heater Control Circuit Low Bank 1 Sensor 3

P0043 points to a low heater control circuit for bank 1 sensor 3. The heater circuit is grounded, missing voltage, or below expected current.

Code details

Generic OBD-II · P0

System: Fuel / Air
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not clear heater codes repeatedly; unresolved heater faults can prevent emissions monitors from completing.

Symptoms of P0043

Check-engine light on, sometimes with rough or uneven running.
Hesitation, surging, or a noticeable change in fuel economy.
Occasionally hard starting or a smell of unburnt fuel.

Common causes of P0043

A failing or contaminated sensor (MAF, MAP, oxygen or air-fuel sensor).
Intake or vacuum leaks, or an exhaust leak near an upstream sensor.
Wiring, connector, or fuel-delivery problems that skew the reading.

Useful checks before replacing parts

Measure heater control voltage, feed, ground, resistance, and current draw while checking for short-to-ground faults.
Inspect sensor wiring near the exhaust, connector fit, fuse or relay supply, heater driver output, and melted insulation.
Compare the low heater circuit with oxygen sensor warm-up behavior, readiness monitor status, and related heater codes.

Related OBD-II codes

These nearby fuel / air entries can help compare wording and pin down the fault area.