Diagnostic codeP0151 refers to the first Oxygen Sensor (O2) located on bench 2, at the front of the catalytic converter. This oxygen sensor measures the amount of oxygen that is expelled by the exhaust. It plays a fundamental role in the control circuit, which constantly verifies that the air-fuel mixture is correct. It sends a signal which is used to handle closed-loop fuel delivery.
The meaning of this basic form code is that the voltage of the O2 (Oxygen Sensor) has remained low for more than 2 minutes. This is understood by the Engine Control Module (ECM) as a low voltage condition, and therefore establishes fault code P0151 OBD2.