Engine diagnostics with control for intermittent ignition

Methods and devices for performing engine diagnosis during the operation of an engine with intermittent firing, while the vehicle is driven is described. Knowing the ignition sequence is used to determine the appropriate timing for the implementation of selected diagnoses and / or to assist in interpreting sensor input or diagnostic results better. According to one aspect selected diagnostics are performed if a single cylinder with respect to a sensor which is used in the diagnosis, several times is ignited isolated. In another aspect, selected diagnoses be made while the engine is operated by using an ignition sequence, which ensures that during a plurality of engine cycles, no cylinders are fired in a first bank of cylinders while cylinders are at least sometimes ignited in a second cylinder bank. The tests described can be performed opportunistically when conditions are appropriate or it can be ordered in order to achieve the desired isolation or shutdown of one or more selected cylinder specific ignition sequences.