S&T Series Blazer, Bravada, Envoy, Jimmy, Rainier, Trailblazer, Xtreme

Passive & Active Diagnostic Tests


A passive test is a diagnostic test that simply monitors a vehicle component or system. 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 EGR active test will force the EGR valve open during closed throttle deceleration and may not force the EGR valve closed during a steady state mode. Either action should result in a change in manifold pressure on the MAP sensor.

Intrusive Diagnostic Tests

An intrusive test refers to a test controlled by the PCM as part of OBD II that may have an effect on vehicle performance or emission levels.