Powertrain Control Module: Notes

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.

For exact location of Powertrain Control Module (PCM), see COMPONENT LOCATIONS in SELF-DIAGNOSTICS - 1.8L VIBE article. PCM may also be referred to as an Electronic Control Module (ECM). Although the 2 units may process different signals, the 2 terms are interchangeable.

The Powertrain Control Module (PCM) is a precision 32-bit microprocessor and is an essential part of the electronic control system. The PCM is located below the Instrument Panel (IP) storage compartment. Communication with the PCM is through the data link connector located below left side, of the IP.

The PCM performs the OBD-II diagnostic tests of the emission related systems. The PCM supplies a buffered voltage, called reference voltage, to the various information sensors and switches. PCM controls most components with an electronic switch that completes a ground circuit when turned ON. The electronic switch is commonly referred to as an output driver. The PCM is also responsible for a self-diagnosis function and a fail-safe function. Battery positive voltage is supplied to the PCM even when the ignition switch is OFF. The battery positive voltage is used for the PCM keep alive memory and the air-fuel ratio adaptive control memory.