Analyzing PCM Data

Look for abnormal events or values that are clearly incorrect. Inspect the signals for abrupt or unexpected changes. For example, during a steady cruise most of the sensor values should be relatively stable. Sensors such as the throttle position (TP) or mass airflow (MAF), as well as RPM that changes abruptly when the vehicle is traveling at a constant speed, are clues to a possible fault area.

Look for agreement in related signals. For example, if the APP1 and APP2 are changed during acceleration, a corresponding change should occur in TP1, TP2, LOAD, RPM and MAF PIDs.

Make sure the signals act in correct sequence. An increase in RPM after the TP1 and TP2 are increased is expected. However, if RPM increases without a TP1 and TP2 change, then a fault may exist.

Scroll through the PID data while analyzing the information. Look for sudden drops or spikes in the values.