About Component Monitors

Component Monitors:

There are several components that will affect vehicle emissions if they malfunction. If one of these components malfunctions the Malfunction Indicator Lamp (Check Engine) will illuminate.

Some of the component monitors are checking for proper operation of the part. Electrically operated components now have input (rationality) and output (functionality) checks. Previously, a component like the engine coolant temperature sensor (ECT) was checked by the PCM for an open or shorted circuit. If one of these conditions occurred, a DTC was set. Now there is a check to ensure that the component is in fact working. This is done by watching for a sensor change over a given time period. In the case of the ECT sensor, if the reading does not move above 60°F after 10 minutes, a DTC will be set.

Refer to the Component Monitors chart for a list of the monitored components, the kind of test and their DTC's shown as the SAE J2012 codes for the Neon: