Passive and Active Diagnostic Tests

A passive test is a diagnostic test which simply monitors a vehicle system or component. Conversely, an active test, actually takes some sort of action when performing diagnostic functions, often in response to a failed passive test. For example, the exhaust gas recirculation (EGR) diagnostic active test will force the EGR valve open during closed throttle deceleration and/or force the EGR valve closed during a steady state. Either action should result in a change in manifold pressure. Some active diagnostic tests, are also intrusive tests. An intrusive diagnostic test is any on-board test, run by the diagnostic management system, that has an effect on vehicle performance or emission levels.