Code Definition

P0043 — HO2S Heater Control Circuit Low (Bank 1 Sensor 3)

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P0043

P0043 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0043 is stored, the module has detected a signal or supply voltage lower than the expected operating range; a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine; and a sensor-related fault — the reported value from the named sensor is out of spec.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0043 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

DTC P0043 sets when the Engine Control Module detects a low voltage or high current condition in the heater control circuit of the oxygen sensor in the bank 1 sensor 3 position, the third sensor in the bank 1 exhaust on vehicles with extra post catalyst monitoring. The heater brings the sensor to operating temperature quickly so it gives a stable signal, and the ECM switches it through a low side driver while watching the circuit. The Low code points to the control circuit being pulled low, most often a short to ground in the heater wiring, a heater element shorted internally and drawing exces...

Join TaT to view the complete code information and diagnostic details.

Quick Facts