PCM Function

The Powertrain Control Module (PCM) supplies either 5 or 12 volts to power various sensors or switches. This is done through resistances in the PCM which are so high in value that a test light will not light when connected to the circuit. In some cases, even an ordinary shop voltmeter will not give an accurate reading because its resistance is too low. Therefore, a 10 megohm input impedance digital voltmeter is required to assure accurate voltage readings.

The Powertrain Control Module (PCM) controls most components with electronic switches which complete a ground circuit when turned ON. These switches are arranged in groups of 4 and 7, called either a surface mounted Quad Driver Module (QDM), which can independently control up to 4 outputs, PCM terminals, or Output Driver Modules (ODM)s, which can independently control up to 7 outputs. Not all outputs are always used.