Patent Document ID: 9476387
Application ID: 13107023
Patent Flag: 1

Claim One:
1. An EGR system diagnostic method, comprising: operating an engine with an EGR bypass valve in a first state for a time greater than a threshold amount of time; requesting a transition in the state of the EGR bypass valve to a second state; determining an EGR gas temperature difference, the EGR gas temperature difference being a difference between a measured EGR gas temperature before and after the transition; comparing the EGR gas temperature difference to a temperature difference threshold; indicating a determined degradation condition of EGR cooler system degradation in response to each of: the request to transition the EGR bypass valve state, a determination that the engine has operated with the EGR bypass valve in the first state for greater time than the threshold amount of time prior to the transition, the EGR gas temperature difference being less than the temperature difference threshold, and an engine exhaust gas oxygen concentration difference being less than an oxygen difference threshold, where the engine exhaust gas oxygen concentration difference is a difference between a measured engine exhaust gas oxygen concentration before and after the transition; and adjusting an actuator responsive to the indication.