Code Definition

P0042 — HO2S Heater Control Circuit (Bank 1 Sensor 3)

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

About P0042

P0042 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 P0042 is stored, the module has detected 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 P0042 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 P0042 identifies a fault in the heater control circuit for the oxygen sensor in the bank 1 sensor 3 position, the third sensor in the bank 1 exhaust stream found on vehicles with additional post catalyst monitoring. This sensor has an internal heater element that the Engine Control Module switches to bring it to operating temperature quickly so it delivers a stable signal for emissions monitoring. P0042 sets when the ECM detects an open, a short, or an out of range condition in that heater control circuit, most often an open heater element or a wiring fault on the low side driver. While th...

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