About 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 Throttle Position Sensor (TPS) 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 working. This is done by watching for a TPS indication of a greater or lesser throttle opening than MAP and engine rpm indicate. In the case of the TPS, if engine vacuum is high and engine rpm is 1,600 or greater and the TPS indicates a large throttle opening, a DTC will be set. The same applies to low vacuum and 1,600 rpm.

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

HIGH AND LOW LIMITS
The PCM compares input signal voltages from each input device with established high and low limits for the device. If the input voltage is not within limits and other criteria are met, the PCM stores a diagnostic trouble code in memory. Other diagnostic trouble code criteria might include engine RPM limits or input voltages from other sensors or switches that must be present before verifying a diagnostic trouble code condition.


Idle/Neutral 2500 RPM/Neutral
Load Value 2% to 8 % of Max Load 2% to 7% of Max Load



LOAD VALUE 8% to 15% of Maximum Load 6% to 12% of Maximum Load