PCM Function

The PCM constantly looks at the information from various sensors and other inputs, and controls systems that affect vehicle performance and emissions. The PCM also performs diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the driver via the Malfunction Indicator Lamp (MIL). When the PCM detects a malfunction, it stores a Diagnostic Trouble Code (DTC). The problem area is identified by the particular DTC that is set. The PCM supplies a buffered voltage (5V or 12V) to various sensors and switches. The input and output devices in the control module include analog to digital converters, signal buffers, counters, multiple function drivers, and output drivers. The multiple function drivers (i.e., EGR control, fuel pump relay) are electronic switches that supply ignition voltage to energize the circuit. The output drivers are electronic switches that, when energized, complete the ground path. Most PCM controlled components are operated via output drivers. The PCM monitors these driver circuits for proper operation. In most cases, if a problem is detected, a DTC corresponding to the controlled device will set.