Patent ID: 8577645

Claim:
An air/fuel imbalance diagnostic system comprising: a filtering module that receives an oxygen signal from an oxygen sensor, that selectively samples the oxygen signal, and that generates imbalance data samples using: a Kalman filter; estimates of the imbalance data samples generated based on a first matrix having elements that reflect a cyclical nature of imbalance data samples of an engine cycle; oxygen signal data generated based on samples of the oxygen signal and samples of a reference oxygen signal determined based on an average of a predetermined number of oxygen signal samples; and estimates of the oxygen signal data generated based on a second matrix having elements that reflect respective contributions of cylinders of a cylinder bank to the oxygen signal; wherein the oxygen sensor measures oxygen in the exhaust from the cylinders of the cylinder bank; an imbalance determination module that determines one air/fuel imbalance (AFIM) value for the entire cylinder bank based on a variance of a plurality of the imbalance data samples; an imbalance diagnostic module that selectively indicates that an AFIM is present in the cylinder bank based on the AFIM value; and a cylinder identification module that, in response to the imbalance diagnostic module indicating that the AFIM is present in the cylinder bank, attributes the AFIM to one of the cylinders of the cylinder bank.