Powertrain Control Module

The PCM is the control center of the vehicle that controls the following:

• Fuel metering system.
• Transmission shifting.
• Ignition timing.
• On-board diagnostics for powertrain functions.

For model specific PCM locations, see POWERTRAIN CONTROL MODULE  under COMPONENT LOCATIONS.

The PCM supplies either 5 or 12 volts to power various sensors and switches. This is done through resistances in the PCM. The resistance is so high in value that a test light does not illuminate when connected to the circuit. In some cases, even an ordinary shop voltmeter does not give an accurate reading because the voltmeters resistance is too low. Therefore, a DVOM with a minimum of 10 megohms input impedance is required to ensure accurate voltage readings.