Description - Monitored Components: Notes

Fig 1: Locating Emission Control Monitored Components

Courtesy of DAIMLERCHRYSLER CORP.

There are several components that will affect vehicle emissions if they malfunction. If one of these components malfunctions, the Malfunction Indicator Lamp (MIL) 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 as well as continuity tests (opens/shorts). Previously, a component like the Throttle Position Sensor (TPS) was checked by the Powertrain Control Module (PCM) for an open or shorted circuit. If one of these conditions occurred, a Diagnostic Trouble Code (DTC) was set. Now there is a check to ensure that the component is working. This is done by watching for a TPS indication of a greater or lesser throttle opening than Manifold Absolute Pressure (MAP) and engine RPM indicate. In the case of the TPS, if engine vacuum is high and engine RPM is 1600 or greater and the TPS indicates a large throttle opening, a DTC will be set. The same applies to low vacuum and 1600 RPM.

Any component that has an associated limp-in will set a fault after 1 trip with the malfunction present.

Refer to the appropriate Engine ELECTRICAL DIAGNOSTICS article for diagnostic procedures. 

The following is a list of the monitored components:

• Catalyst Monitor
• Comprehensive Components
• Exhaust Gas Recirculation (EGR)
• Fuel Control (rich/lean)
• Oxygen Sensor Monitor
• Oxygen Sensor Heater Monitor
• Purge
• Misfire
• Evaporative Vacuum Leak Detection (EVLD)