An Oxygen Sensor generates a voltage that varies when the amount of oxygen present in the exhaust gas changes. By using this data, the PCM (Powertrain Control Module) can make short-term fuel adjustments so that the air-fuel mixture is kept within appropriate levels for proper exhaust system performance. Although the Oxygen Sensor tells the PCM whether the mixture is rich or lean, its design cannot tell the PCM how rich or lean is the mix. With this in mind, for the PCM to maintain the ideal mixture, it must vary the Oxygen Sensor signal voltage between rich and lean continuously and several times per second, and then adjust the injector pulse width.
In contrast, an air/fuel ratio sensor is based on a voltage differential between two independent measuring elements, which makes possible a stoichiometric mixture is maintained. If the PCM observes out-of-range voltages on the A/F Sensor in the signal output circuit, the fault code P1130 OBDII will be set.