Patent attributes
Methods and apparatus for conducting engine related diagnostics during cylinder cutoff (DCCO) operation of an engine are described. In one aspect, changes in the amount of oxygen in the exhaust system are monitored while the engine is operating in the DCCO mode. Changes in the oxygen level are then analyzed to determine various faults. Some of the faults that can be detected using this approach include cylinder deactivation faults and exhaust system leak faults. In another aspect, the rate of change of manifold pressure within the air intake manifold is monitored while operating the engine in a DCCO mode with the throttle closed. A fault indicative of potential air leakage into the air intake manifold is indicated when it is determined that the rate of change of the manifold pressure exceeds a designated threshold.
