Monitored Components

There are several electrical components that will affect vehicle emissions if they malfunction. If one of these components is malfunctioning, a Diagnostic Trouble Code (DTC) will be set by either the Powertrain Control Module (PCM) or the Engine Control Module (ECM). The Malfunction Indicator Lamp (MIL) will then be illuminated when the engine is running.

These electrically operated components have input (rationality) and output (functionality) checks. A check is done by one or more components to check the operation of another component.

Example: The Intake Manifold Air Temperature (IAT) sensor is used to monitor intake manifold air temperature over a period of time after a cold start If the temperature has not risen to a certain specification during a specified time, a Diagnostic Trouble Code (DTC) will be set for a problem in the manifold air heater system.

All open/short circuit checks, or any component that has an associated limp-in will set a DTC and trigger the MIL after 1 trip with the malfunction present. Components without an associated limp-in will take two trips to illuminate the MIL.