Abstract: Methods and systems are provided for on-board diagnostics of an exhaust gas recirculation (EGR) system of an engine coupled to a hybrid vehicle. In one example, a method may include, upon receiving an engine shut-down request, prior to engine spin-down, rotating the engine at an idling speed via an electric motor and carrying out diagnostics of the EGR system. EGR diagnostics may include estimating a ratio of accumulated difference between a measured EGR flow and an EGR limit to accumulated intake air flow, over a duration of time, and indicating EGR system degradation in response to the ratio being higher than a threshold.

Abstract: Methods and systems are provided for on-board diagnostics of an exhaust gas recirculation (EGR) system of an engine coupled to a hybrid vehicle. In one example, a method may include, upon receiving an engine shut-down request, prior to engine spin-down, rotating the engine at an idling speed via an electric motor and carrying out diagnostics of the EGR system. EGR diagnostics may include estimating a ratio of accumulated difference between a measured EGR flow and an EGR limit to accumulated intake air flow, over a duration of time, and indicating EGR system degradation in response to the ratio being higher than a threshold.

Abstract: To provide a substrate of aluminum with a dark surface layer of high absorption/emission ratio for luminous energy, the degreased and pickled substrate is immersed in a hot chromating bath until an oxide coating of not more than 2.5.mu. thickness is formed thereon. This coating is then colored black in a hot, acidic dyeing solution (pH between about 0.5 and 5) of potassium permanganate and a nitrate of cobalt or copper.